# SIMULATING N₂O EMISSIONS USING THE STICS SOIL-CROP MODEL IN LOW-INPUT CROPPING SYSTEMS IN SW FRANCE

Daniel Plaza-Bonilla¹²*, Joël Léonard³, Céline Peyrard³, Pierre Perrin¹, Bruno Mary³, Eric Justes¹

¹INRA, UMR 1248 AGIR, Toulouse, France

²EEAD-CSIC, Soil and Water Department, Zaragoza, Spain

³INRA, UR Agrolmpact, Barenton-Bugny, France

*E-mail: dplaza@eead.csic.es

INRA
SCIENCE & IMPACT

<figure><img src="image_1.png" /></figure>

## Introduction

* Soil N₂O emissions account for ca. 40% of total agricultural greenhouse gas emissions in EU (Eur. Environ Agency, 2015).

* Need to quantify N₂O emissions and identify mitigation options, in particular in low input systems where N fertilizer is reduced.

* Process based models are able to integrate a range of pedoclimatic conditions and agricultural management practices.

**Objective:** test the ability of the soil-crop model STICS to simulate the emissions of N₂O in low-input cropping systems

## Materials and Methods

* MicMac cropping systems experiment (2010-): Auzeville, SW France (43.5 N, 1.5 W). Annual rainfall: 685 mm; Temperature: 13.7°C; PET: 905 mm.

* Cropping systems: 3-yr innovative prototypes (with or without cover crops) as an alternative to the traditional durum wheat-sunflower rotation (Fig. 1).

<figure><img src="image_2.png" /><figcaption>Figure 1 Conceptual diagram of the 3-year cropping systems tested.</figcaption></figure>

<figure><img src="image_3.png" /><figcaption>Figure 2 Automatic chambers for N₂O fluxes quantification</figcaption></figure>

* N₂O fluxes determined 4 times per day using automatic chambers (0.7 x 0.4 m) (Fig. 2) (Peyrard et al., 2016).

* Different N₂O-driving variables measured: soil temperature, mineral N, water content and bulk density.

* Simulation of N₂O using STICS model (Brisson et al., 1998; Bessou et al., 2010) (Fig. 3). Plant and soil parameters calibrated and evaluated on the site (Plaza-Bonilla et al., 2015).

<figure><img src="image_4.png" /><figcaption>Figure 3 STICS model functioning: inputs required, some simulated processes and outputs used.</figcaption></figure>

## Results

* Our preliminary results show a fairly good capacity of the STICS model to simulate soil N₂O emissions, in different cash crop and cover crop periods of such complex rotations in low-input cropping systems, including grain legumes and cover crops.

* STICS simulated reasonably well different N₂O driving factors, such as soil temperature, and water, nitrate and ammonium contents in the 0-15 cm soil layer (Fig. 4).

* Simulated cumulative N₂O emissions during different faba bean and durum wheat cropping seasons (2010-2011, 2011-2012, 2012-2013 and 2013-2014) showed similar ranges of magnitude (i.e. between 0.45 and 1.7 kg N₂O-N ha⁻¹) than observed ones (Fig. 5).

* STICS seemed able to capture the main trends of N₂O emissions, with greater values at higher levels of soil nitrate during the growing season of crops and cover crop incorporation in the soil. However, the model predicted some peaks of N₂O after N fertilizer application that were not observed in the field (Fig. 6) indicating that we still need to better understand the impact of driving variables on N₂O emissions.

<figure><img src="image_5.png" /><figcaption>Figure 5 Observed and simulated cumulative N₂O emissions of different faba bean (FB) and durum wheat (W) cropping seasons.</figcaption></figure>

<figure><img src="image_6.png" /><figcaption>Figure 6 Observed and simulated N₂O emissions dynamics of a durum wheat-sorghum rotation with vetch-phaceliel as cover crop.
*Indicate nitrogen fertilizer applications</figcaption></figure>

<figure><img src="image_7.png" /></figure>

## Conclusions

Our preliminary results show the potential of the STICS soil-crop model to simulate the range of values of N₂O emissions of such complex crop rotations with cover crops without great time investments in calibration.

Some improvement is still needed to better mimic the dynamics of emissions and obtain more precise estimations of the impact of agricultural management practices and cropping systems on N₂O emissions.

## References

Bessou, C. (2010), Eur. J. Soil Sci., 61, 348-363.
Brisson, N. et al. (1998), Agronomie 18, 311-346.
EEA (2015), Trends and projections in Europe. ISSN 1977-8449.
Peyrard, C. et al. (2016), Agric. Ecosys. Environ. 224, 145-156.
Plaza-Bonilla, D. et al. (2015), Agric. Ecosys. Environ. 212, 1-12.

**Acknowledgements:** We acknowledge the field and laboratory assistance of Didier Chesneau, Michel Labarrère and Didier Raffaillac. This research was supported by GLIP FP6 EU Project, French ANR-09-STRRA-06 (MicMac project), French Ministry of Agriculture CASDAR Leg-N-GES project and French National Research Agency ANR-13-AGRO LEGITIMES project.
# Simulating N2 O emissions using the stics soil-crop model in low-input cropping systems in sw France

Daniel Plaza Bonilla, Joël Léonard, Céline Peyrard, Pierre Perrin, Bruno Mary, Eric Justes

## ► To cite this version:

Daniel Plaza Bonilla, Joël Léonard, Céline Peyrard, Pierre Perrin, Bruno Mary, et al. Simulating N2 O emissions using the stics soil-crop model in low-input cropping systems in sw France. 19. Nitrogen workshop, Jun 2016, Skara, Switzerland., 464 p., 2016, Efficient use of different sources of nitrogen in agriculture - from theory to practice. *hal-01602868*

HAL Id: hal-01602868

https://hal.science/hal-01602868

Submitted on 3 Jun 2020

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<figure><img src="image_1.png" /></figure>
N 19th
NITROGEN
WORKSHOP

Efficient use of different sources of nitrogen in agriculture
– from theory to practice

Skara, Sweden 27 June – 29 June 2016

<figure><img src="image_2.png" /></figure>

Abstracts

<figure><img src="image_3.png" /></figure>
# Contents

## Oral presentations

<table><tr><td>AGRONOMIC CRITERIA TO DESIGN A VARIABLE RATE NITROGEN STRATEGY IN CROPPING SYSTEMS</td><td>14</td></tr><tr><td>REFINED N-FERTILIZATION OF WINTER WHEAT</td><td>17</td></tr><tr><td>SENSING COINCIDENT NITROGEN DEFICIENCY AND WATER STRESS IN WHEAT</td><td>18</td></tr><tr><td>DETERMINATION OF FERTILISER REQUIREMENTS IN DAIRY PRODUCTION SYSTEMS BASED ON PASTURE NITROGEN CONCENTRATIONS</td><td>20</td></tr><tr><td>APPLICATION OF A NITRIFICATION INHIBITOR (PIADIN®) ALONG WITH SLURRY USING STRIP TILL APPROACH FOR OPTIMIZING N FERTILIZER EFFICIENCY - LABORATORY AND FIELD RESULTS</td><td>22</td></tr><tr><td>PLANT-MEDIATED NITROGEN CYCLING IN AGRICULTURAL SYSTEMS</td><td>24</td></tr><tr><td>NITROGEN BUDGETS OF ORGANIC AND CONVENTIONAL CROPPING SYSTEMS: SIGNIFICANCE OF SPECIFIC INPUTS AND OF SOIL NITROGEN STOCKS</td><td>26</td></tr><tr><td>DESIGNING AND EVALUATING ARABLE CROPPING SYSTEMS WITH CASH AND COVER CROP LEGUMES IN SOLE CROP AND INTERCROP TO IMPROVE NITROGEN USE EFFICIENCY</td><td>28</td></tr><tr><td>NITROGEN - LOSS, SOURCE, TRANSFORMATION AND ATTENUATION WITHIN AN INTENSIVE DAIRY FARM IN SE IRELAND</td><td>30</td></tr><tr><td>NITROGEN USE EFFICIENCY - AN IMPORTANT INDICATOR FOR THE UTILIZATION OF NITROGEN IN CROP PRODUCTION</td><td>32</td></tr><tr><td>IMPROVED MANURE MANAGEMENT - FROM RESEARCH RESULTS TO IMPLEMENTATION ON FARM</td><td>34</td></tr><tr><td>DESIGNING AN INNOVATIVE NITROGEN FERTILIZATION METHOD FOR WHEAT BASED ON THE DIAGNOSIS OF USES OF CURRENT TOOLS</td><td>38</td></tr><tr><td>CROPSAT - A SATELLITE-BASED SUPPORT SYSTEM FOR VARIABLE-RATE SUPPLEMENTARY FERTILIZATION OF NITROGEN IN SMALL GRAINS PRODUCTION IN SCANDINAVIA</td><td>40</td></tr><tr><td>FARMER ATTITUDES AND POTENTIAL BARRIERS TO THE USE OF PROCESSED ORGANIC FERTILISERS</td><td>42</td></tr><tr><td>NITROGEN USE EFFICIENCY WITHIN THE VITTEL MINERAL WATERSHEDS: A PARTICIPATORY INVESTIGATION AIMING AT SETTING BEST MANAGEMENT PRACTICES AT DIFFERENT SCALES</td><td>44</td></tr><tr><td>ECOLOGY OF MICROBES CAUSING N LOSS AND RETENTION IN ARABLE SOILS</td><td>47</td></tr><tr><td>COVER CROPS TRIGGER NITROGEN UPTAKE BY SOIL MICROORGANISMS</td><td>50</td></tr><tr><td>DINITROGEN EMISSIONS FROM CODENITRIFICATION IS THE MAIN LOSS PATHWAY FROM URINE AMENDED GRASSLAND SOIL</td><td>52</td></tr><tr><td>OPPOSING EFFECTS OF NITROGEN AND PHOSPHORUS ON SOIL MICROBIAL METABOLISM AND SOIL CARBON STORAGE</td><td>54</td></tr><tr><td>NITRIFICATION, DENITRIFICATION AND NITROUS OXIDE EMISSION AS AFFECTED BY SOIL PH MANAGEMENT</td><td>56</td></tr><tr><td>DEVELOPMENT TRENDS AND SOLUTION SCENARIOS FOR IMPROVED N EFFICIENCY</td><td>58</td></tr></table>
<table>
  <tbody>
    <tr>
      <td>NITROGEN CASCADE AT THE LANDSCAPE SCALE: MODELLING THE EFFECT OF CLIMATE, SOILS AND AGRICULTURE ON DIRECT AND INDIRECT N EMISSIONS IN CONTRASTED RURAL SITES</td>
      <td>60</td>
    </tr>
    <tr>
      <td>USING FIELD NITROGEN BALANCES AS AN INDICATION OF NITROGEN SOURCE PRESSURE CHANGE ON WATER QUALITY</td>
      <td>62</td>
    </tr>
    <tr>
      <td>IMPACT OF NITROGEN USE IN AGRICULTURE ON GLOBAL EMISSIONS OF NITROUS OXIDE (N2O) AND CARBON DIOXIDE (CO2)</td>
      <td>64</td>
    </tr>
    <tr>
      <td>EFFECTIVENESS OF AGRI-ENVIRONMENTAL MEASURES TO REDUCE AIR AND WATER N POLLUTION ACROSS VENETO REGION, ITALY</td>
      <td>66</td>
    </tr>
    <tr>
      <td>CHANGES IN FOOD CONSUMPTION PATTERNS AND NITROGEN DEMAND RELATED TO CHINA'S URBANIZATION</td>
      <td>68</td>
    </tr>
    <tr>
      <td colspan="2">Poster presentations presented in parallel workshops</td>
    </tr>
    <tr>
      <td>IMPROVING NITROGEN RECOVERY FROM GREEN MANURE ON CONTRASTING SOIL TYPES UNDER COLD CLIMATE CONDITIONS</td>
      <td>72</td>
    </tr>
    <tr>
      <td>NITROGEN TRANSFER IN THREE-SPECIES MIXTURES OF GRASS, CLOVER AND FORBS</td>
      <td>74</td>
    </tr>
    <tr>
      <td>NITROGEN SUPPLY AND DYNAMICS IN WINTER WHEAT FOLLOWING DIFFERENT GRAIN LEGUMES IN ORGANIC FARMING ROTATIONS</td>
      <td>76</td>
    </tr>
    <tr>
      <td>BIOLOGICAL NITROGEN FIXATION AND TRANSFER IN A HIGH LATITUDE GRASS-CLOVER GRASSLAND</td>
      <td>78</td>
    </tr>
    <tr>
      <td>STRATEGIC BIOMASS MANAGEMENT INCREASES NITROGEN FIXATION IN THE GREEN MANURE LEY OF AN ORGANIC ARABLE CROPPING SYSTEM</td>
      <td>80</td>
    </tr>
    <tr>
      <td>LARGE VARIATION IN NITROGEN EFFICIENCY AMONG ORGANIC AND NON-ORGANIC DAIRY FARMS</td>
      <td>82</td>
    </tr>
    <tr>
      <td>SIGNIFICANCE OF LEGUME COVER CROPS AS NITROGEN SUPPLY FOR CORN IN AN ORGANIC MANAGED SOYBEAN-WINTER_WHEAT-CORN SYSTEM IN SOUTHERN ONTARIO, CANADA</td>
      <td>84</td>
    </tr>
    <tr>
      <td>SYMBIOTIC NITROGEN FIXATION AND NITROGEN FERTILIZATION VALUE OF LEGUME GREEN MANURES IN ORGANIC AGRICULTURE</td>
      <td>86</td>
    </tr>
    <tr>
      <td>PREDICTING GRAIN YIELD AND PROTIEN CONTENT OF WINTER BARLEY WITH AN ACTIVE OPTICAL SENSOR</td>
      <td>87</td>
    </tr>
    <tr>
      <td>POTATO CROP NITROGEN STATUS ASSESSEMENT COMBINING OPTICAL INDICATORS BASED ON LEAF CHLOROPHYLL AND FLAVONOIDS CONTENTS.</td>
      <td>89</td>
    </tr>
    <tr>
      <td>MITIGATION OF NITROUS OXIDE EMISSIONS USING A NITRIFICATION INHIBITOR, ALTERNATIVE PASTURE AND FORAGE PLANTS AND GIBBERELLIC ACID</td>
      <td>91</td>
    </tr>
    <tr>
      <td>INHIBITION OF BACTERIAL AND FUNGAL NH<sub>4</sub>-N OXIDATION BY THE NITRIFICATION INHIBITOR DICYANDIAMIDE (DCD) IN A TEMPERATE GRASSLAND SOIL</td>
      <td>93</td>
    </tr>
    <tr>
      <td>THE EFFECT OF NITROGEN STABILISERS ON NITROUS OXIDE EMISSIONS AND SPRING BARLEY GRAIN YIELD FROM A FREE-DRAINING LOAM</td>
      <td>95</td>
    </tr>
    <tr>
      <td>EFFECTS OF ORGANIC MATTER INPUT ON NUTRIENT BALANCES, NITRATE LEACHING AND CROP YIELD IN A LONG TERM EXPERIMENT ON SANDY SOILS IN THE NETHERLANDS</td>
      <td>97</td>
    </tr>
    <tr>
      <td>EFFECTIVENESS OF NITROGEN INHIBITORS AND APPLICATION METHODS ON REDUCING AMMONIA VOLATILIZATION AND NITROUS OXIDE EMISSIONS FROM SOILS</td>
      <td>99</td>
    </tr>
  </tbody>
</table>
<table>
  <tbody>
    <tr>
      <td>THE EFFECTIVENESS OF SOME SELECTED MANAGEMENT STRATEGIES FOR REDUCING NITROGEN LEACHING RISK FROM DAIRY GRAZING SYSTEMS IN SOUTHERN NEW ZEALAND</td>
      <td>101</td>
    </tr>
    <tr>
      <td>CONTROLLED DRAINAGE AS MEASURE TO REDUCE NITRATE LEACHING IN DIFFERENT SOIL AND CROPPING SYSTEMS</td>
      <td>103</td>
    </tr>
    <tr>
      <td>A SYSTEM N BALANCE FOR A PASTURE-BASED SYSTEM OF DAIRY PRODUCTION UNDER MOIST MARITIME CLIMATIC CONDITIONS</td>
      <td>105</td>
    </tr>
    <tr>
      <td>NITROGEN BUDGET ESTIMATED FOR BEEF OPERATIONS ACROSS CANADA</td>
      <td>107</td>
    </tr>
    <tr>
      <td>NITROGEN BALANCE AND NITROGEN FOOTPRINT OF BIOGAS CROPPING SYSTEMS: SHORT-TERM EFFECTS OF BIOGAS RESIDUE APPLICATION</td>
      <td>109</td>
    </tr>
    <tr>
      <td>INDICATORS FOR NITROGEN USE EFFICIENCY BASED ON TOTAL NITROGEN FIXATION AS A COMPLEMENT TO TRADITIONAL SURPLUS-BASED INDICATORS</td>
      <td>111</td>
    </tr>
    <tr>
      <td>PREDICTORS OF GROSS NITROGEN PROCESSES IN AGRICULTURAL SOILS: DOES QUALITY MATTER?</td>
      <td>114</td>
    </tr>
    <tr>
      <td>LONG TERM (35 Y) EFFECTS OF MANURE AND FERTILIZER-N APPLICATION ON N BALANCE IN SOIL, CROP YIELD AND N UPTAKE EFFICIENCY</td>
      <td>116</td>
    </tr>
    <tr>
      <td>AGRICULTURAL MANAGEMENT AFFECTS BELOW GROUND NITROGEN AND CARBON INPUTS – A SYNTHESIS OF EIGHT YEARS ROOT RESEARCH IN SWISS LONG TERM EXPERIMENTS</td>
      <td>118</td>
    </tr>
    <tr>
      <td>URBAN AND AGRICULTURAL WASTE APPLICATION AFFECTS NITROGEN TURNOVER, CROP UPTAKE EFFICIENCY AND SOIL FERTILITY IN LONG-TERM FIELD EXPERIMENT</td>
      <td>120</td>
    </tr>
    <tr>
      <td>ESTIMATING NITROUS OXIDE FLUXES FROM AGRICULTURAL SOILS AT EUROPEAN SCALE USING A CROP GENERIC META-MODEL</td>
      <td>122</td>
    </tr>
    <tr>
      <td>N<sub>2</sub>O EMISSIONS FROM ORGANIC FERTILIZERS AND CROP RESIDUE MIXTURE IN SUGARCANE CROPPING</td>
      <td>124</td>
    </tr>
    <tr>
      <td>A NEW APPROACH TO ESTIMATE NITROUS OXIDE EMISSIONS FROM ARABLE CROPS IN THE UNITED KINGDOM?</td>
      <td>126</td>
    </tr>
    <tr>
      <td>MULTI-FUNCTIONAL COVER CROPS FOR CROPPING SYSTEMS IN SOUTHERN SCANDINAVIA AND FINLAND</td>
      <td>129</td>
    </tr>
    <tr>
      <td>IMPACTS OF DECLINING ROTATION DIVERSITY ON NITROGEN USE EFFICIENCY IN MAIZE</td>
      <td>131</td>
    </tr>
    <tr>
      <td>LEGUME-BASED CATCH CROPS FOR ECOLOGICAL INTENSIFICATION</td>
      <td>133</td>
    </tr>
    <tr>
      <td>IMPROVING NUTRIENT USE EFFICIENCY AND REDUCING ENVIRONMENTAL LOSSES OF NITROGEN: INSIGHTS FROM A PROCESS-BASED MODEL AND ON-FARM TRIALS</td>
      <td>135</td>
    </tr>
    <tr>
      <td>ESTABLISHING THE NITROGEN DILUTION CURVE FOR POTATO IN BELGIUM</td>
      <td>137</td>
    </tr>
    <tr>
      <td>IMPACT OF VARIETIES ON BREAD WHEAT NITROGEN USE EFFICIENCY FOR YIELD AND GRAIN PROTEIN CONTENT: WHEN AGRONOMY MEETS GENETICS</td>
      <td>139</td>
    </tr>
    <tr>
      <td>NITROGEN FERTILISER FORMULATION: THE IMPACT ON YIELD AND GASEOUS EMISSIONS IN TEMPERATE GRASSLAND</td>
      <td>141</td>
    </tr>
    <tr>
      <td>COMPARATIVE ENVIRONMENTAL ASSESSMENT OF AMMONIUM NITRATE VERSUS UREA FERTILIZER ON A TYPICAL CROP ROTATION</td>
      <td>143</td>
    </tr>
  </tbody>
</table>
N FERTILIZER TYPE HAS SMALL EFFECT ON DIRECT N2O EMISSIONS
BUT STRONG INFLUENCE ON THE TOTAL CLIMATE IMPACT OF
RAPESEED CROP ROTATIONS 145

SCENARIO MODELING OF AMMONIA EMISSIONS FROM SURFACE
APPLIED UREA UNDER TEMPERATE CONDITIONS - APPLICATION
EFFECTS AND MODEL COMPARISON 147

EFFECTS OF CRUSHING AND DRYING ORGANIC PRODUCTS ON
THEIR NITROGEN AND CARBON MINERALIZATION IN SOIL INCUBATIONS 149

STRIP-TILLAGE COMBINED WITH SLURRY BAND INJECTION BELOW THE
MAIZE ROW - A NEW APPROACH TO IMPROVE THE NITROGEN USE
EFFICIENCY OF ORGANIC FERTILIZERS 151

COMPARISON OF THE EFFICIENCY OF NITRIFICATION INHIBITORS DMPP
AND DMPSA ON A MAIZE-RYEGRASS CROP ROTATION 154

EFFECT OF CONTRASTING APPLICATION TECHNIQUES ON AMMONIA EMISSIONS
FOLLOWING FOOD-BASED DIGESTATE APPLICATIONS TO GRASSLAND 156

WHICH SOIL DATASET SHOULD I USE? SIMULATION UNCERTAINTIES FOR
REGIONAL NITROGEN MANAGEMENT 158

STRENGTH AND WEAKNESSES OF EARLY WARNING MONITORING
SYSTEMS FOR WATER QUALITY PROTECTION: MONITORING EFFECTS
OF MEASURES TO REDUCE NITRATE LEACHING 160

NITROGEN LOSSES FROM AUSTRIAN AGRICULTURAL SOILS - MODELLING
TO EXPLORE TRADE OFF-EFFECTS (NITROAUSTRIA) 162

DETERMINING SPATIAL IRREGULARITIES OF NITRATE
CONCENTRATIONS IN IRRIGATION RETURN FLOWS OF
MEDITERRANEAN IRRIGATION SUB-CATCHMENTS 164

INTERACTIONS BETWEEN TILLAGE SYSTEM, NITROGEN
FERTILIZATION AND COVER CROPPING DETERMINE N₂O FLUXES 166

OPPORTUNITIES TO REDUCE NITROUS OXIDE EMISSIONS
FROM AGRICULTURAL SOILS: EMISSION REDUCTION POTENTIALS AND COSTS 168

NO-TILLAGE AND MEDIUM RATES OF PIG SLURRY FERTILIZATION
MITIGATE YIELD-SCALED N2O EMISSIONS IN DRYLAND
MEDITERRANEAN AGROECOSYSTEMS 171

SPATIAL VARIATION IN SOIL PH CONTROLS OFF-SEASON N₂O EMISSIONS 173

NITROGEN-USE EFFICIENCY OF DIFFERENT FORAGE-BASED
DAIRY PRODUCTION SYSTEMS 175

MODELLING THE INTERACTIONS BETWEEN THE MILK C AND N
FOOTPRINT FROM INTENSIVE DAIRY FARMS IN NORTHERN SPAIN. 177

MEASURES TO REDUCE THE GREENHOUSE GAS EMISSIONS
FROM DAIRY FARMING AND THEIR EFFECT ON NITROGEN FLOW 179

NITROGEN EXCRETION IN PREGNANT SUCKLER COWS FED
DIFFERENT ROUGHAGES AD LIBITUM 182

## Poster presentations

PROTEIN QUALITY OF FORAGES FOR RUMINANTS 185

UPGRADING OF ESSENTIAL AMINO ACIDS IN PLANTS THROUGH
BEEF PRODUCTION FOR HIGHER NUTRITIONAL VALUE FOR HUMANS 187
EFFECT OF ORGANIC FERTILIZATION ON N₂O EMISSIONS AND WHEAT CROP YIELD AND QUALITY 190

EVALUATION OF CARBON DIOXIDE EMISSION FACTOR FROM UREA APPLIED IN PADDY SOIL DURING RICE CULTIVATION 192

DIFFERENT RESPONSES OF NITROGEN FERTILIZATION ON METHANE EMISSION IN RICE PLANT INCLUDED AND EXCLUDED SOILS DURING CROPPING SEASON 194

REAL TIME ANALYSIS OF DAIRY SLURRY FOR PRECISE FERTILIZATION– PERFORMANCE OF AN ON-LINE NEAR INFRARED REFLECTANCE SYSTEM 196

GROWTH, WATER AND NITROGEN USE EFFICIENCY UNDER DRIP IRRIGATION ON WHEAT GROWN ON ARID REGION 198

LAND USE EFFECTS ON C AND N DYNAMICS IN AN AREA NEAR BRAUNSCHWEIG, NORTH GERMANY 199

SIMULATING N₂O EMISSIONS USING THE STICS SOIL-CROP MODEL IN LOW-INPUT CROPPING SYSTEMS IN SW FRANCE 203

AMMONIA EMISSIONS FROM TWO NATURALLY VENTILATED CATTLE BUILDINGS IN IRELAND 205

AMMONIA AND NITROUS OXIDE LOSSES FROM MECHANICALLY TURNED CATTLE MANURE WINDROWS: A REGIONAL COMPOSTING NETWORK 207

FURTHER DEVELOPMENT AND APPRAISAL OF THE GEOLOGICAL SURVEY OF IRELAND'S POTENTIALLY DENITRIFYING BEDROCK MAP 209

MYCORRHIZAL INOCULUM EFFECTS ON NITROGEN UPTAKE AND LEACHING IN ENERGY CROP SPECIES FERTILIZED WITH DIGESTATE LIQUID FRACTION IN MESOCOSM CONDITION 211

SIMULATIONS OF NITROGEN DYNAMICS AND LOSSES IN AGRICULTURAL SOILS IN LOMBARDY REGION UNDER DIFFERENT CROPPING SYSTEMS 213

EFFECT OF INTEGRATED FERTILIZATION AND COVER CROPPING ON N₂O LOSSES IN AN IRRIGATED MEDITERRANEAN MAIZE FIELD 215

STATISTICAL MATCHING TO OBTAIN BETTER ESTIMATES AT REGIONAL SCALE 217

PROVISION OF DICYANDIAMIDE IN SUPPLEMENTARY FEED AS A TARGETED NITROGEN MITIGATION STRATEGY FOR GRAZING CATTLE: PROOF-OF EFFICACY 219

DETERMINING THE ROLE OF FUNGI AND BACTERIA IN CO-DENITRIFICATION 221

N-SMART™ SUSTAINABILITY MODEL: THE SCIENCE BEHIND IT 222

N₂O EMISSIONS OF IRRIGATED MAIZE MANAGED UNDER DIFFERENT SOIL TILLAGE SYSTEMS AND N FERTILIZATION RATES IN A MEDITERRANEAN AGROECOSYSTEM 225

UREASE ACTIVITY AND POTENTIALLY MINERALIZABLE NITROGEN INFLUENCED BY DIFFERENT SOIL MANAGEMENT SYSTEMS 227

FERTILISER N RECOVERY AND MINERALISATION SUPPLY IN A MEDITERRANEAN MID-TERM COVER CROP-MAIZE ROTATION SYSTEM 229

EFFECTS OF MYCORRHIZAL INOCULUM AND DIGESTATE FERTILIZATION ON TRITICALE (×TRITICOSECALE WITTMACK) PRODUCTION USING FUNGICIDES COATED SEEDS 231

MANAGEMENT MATTERS: TESTING A MITIGATION STRATEGY OF NITROUS OXIDE EMISSIONS ON MANAGED GRASSLAND 233
<table>
  <tbody>
    <tr>
      <td>MODELING WATER-NITROGEN-CARBON FEEDBACKS ON PLANT BIOMASS ACCUMULATION UNDER ELEVATED CO<sub>2</sub> USING A COUPLED HYDROLOGICAL-PLANT GROWTH MODEL</td>
      <td>234</td>
    </tr>
    <tr>
      <td>NITROGEN EMISSIONS FROM ARABLE LAND WITH DIFFERENT NITROGEN FERTILIZATION</td>
      <td>236</td>
    </tr>
    <tr>
      <td>SHORT TERM EFFECTS OF POLYACRYLAMIDE AND DICYANDIAMIDE ON C AND N MINERALISATION IN A SANDY LOAM SOIL</td>
      <td>238</td>
    </tr>
    <tr>
      <td>CAN NITRIFICATION INHIBITORS AND MANURE TMING IMPACT NITROUS OXIDE EMISSIONS FOLLOWING FIELD INJECTION OF LIQUID MANURE?</td>
      <td>241</td>
    </tr>
    <tr>
      <td>EFFECTIVENESS OF NITRIFICATION INHIBITORS AND CONTRAST OF FIELD VERSUS INCUBATION EXPERIMENTS ON SOIL NITROGEN KINETICS AND NITROUS OXIDE EMISSIONS</td>
      <td>242</td>
    </tr>
    <tr>
      <td>DEPOLYMERIZATION AND MINERALIZATION - INVESTIGATING THE RATE LIMITING STEP BY A NOVEL <sup>15</sup>N TRACING MODEL</td>
      <td>244</td>
    </tr>
    <tr>
      <td>RESIDUAL EFFECT OF DIFFERENT NITROGEN FERTILIZATION ON REED CANARY GRASS, (PHALARIS ARUNDINACEA L.) IN MONOCULTURE AND IN MIXTURE WITH GOAT'S RUE, (GALEGA ORIENTALIS, LAM.)</td>
      <td>245</td>
    </tr>
    <tr>
      <td>EFFECT OF DIGESTATE SOLID FRACTION ON HORTICULTURE SUCCESSION YIELD AND SOIL CARBON DIOXIDE EMISSION</td>
      <td>247</td>
    </tr>
    <tr>
      <td>IMPROVEMENT OF WINE TERROIR MANAGEMENT ACCORDING TO BIOGEOCHEMICAL CYCLE OF NITROGEN IN SOIL</td>
      <td>249</td>
    </tr>
    <tr>
      <td>MICROBIAL NITROGEN RECYCLING IN AGRICULTURAL SOIL - DOES FERTILISATION WEAKEN DISSIMILATORY NITRATE REDUCTION TO AMMONIUM?</td>
      <td>251</td>
    </tr>
    <tr>
      <td>DENITRIFICATION OF GROUNDWATER INDUCED BY TWO CARBON SOURCES: VEGETAL COMPOST AND CRUSHED PALM TREE LEAVES</td>
      <td>253</td>
    </tr>
    <tr>
      <td>NITROGEN MINERALIZATION FROM CLOVER LEAVES: EFFECT OF SOIL TYPE AND LOW TEMPERATURE</td>
      <td>255</td>
    </tr>
    <tr>
      <td>EFFICIENCY OF CONTROLLED DRAINAGE AND LAND DRAINAGE SYSTEM IN IMPROVING WATER SAVING AND REDUCING NON-POINT SOURCE POLLUTION IN A FIVE-YEAR TRIAL</td>
      <td>257</td>
    </tr>
    <tr>
      <td>GRAZING BEHAVIOUR, URINE COMPOSITION AND SOIL PROPERTIES ARE KEY DRIVERS OF NITROUS OXIDE EMISSIONSFROM LIVESTOCK URINE IN THE UPLANDS (UPLANDS-N2O)</td>
      <td>259</td>
    </tr>
    <tr>
      <td>FERTILIZATION &amp; ENVIRONMENT JOINT TECHNOLOGICAL NETWORK - CONCEPTS, PROJECTS AND TOOLS USED AROUND FERTILIZATION AND MANAGEMENT OF BIOGEOCHEMICAL CYCLES</td>
      <td>261</td>
    </tr>
    <tr>
      <td>MECHANISTIC INSIGHTS INTO THE EFFECTS OF NITROGEN FERTILIZER APPLICATION ON N<sub>2</sub>O-EMISSION PATHWAYS IN ACIDIC SOIL OF A TEA PLANTATION</td>
      <td>263</td>
    </tr>
    <tr>
      <td>NITRIFICATION INHIBITORS: NITROGEN USE EFFICIENCY AND RESIDUAL EFFECT</td>
      <td>264</td>
    </tr>
    <tr>
      <td>FEATURES IN VILLAGE-SCALE NITROGEN FLOW IN THE LOWER REACH OF YANGTZE RIVER, CHINA</td>
      <td>266</td>
    </tr>
    <tr>
      <td>INTEGRAL ASSESSMENT OF FARM RESULTS BY BENCHMARKING</td>
      <td>269</td>
    </tr>
    <tr>
      <td>CALCULATING NITROGEN FOOTPRINTS ALONG THE CHAIN FROM AGRICULTURE TILL RESIDUE WHEREABOUTS ON THE EXAMPLE OF FOOD PROVIDED AT A CONFERENCE</td>
      <td>271</td>
    </tr>
  </tbody>
</table>
<table>
  <tbody>
    <tr>
      <td>EVALUATING SCENARIOS ON THE NITROGEN CASCADE IN RURAL LANDSCAPE MODELLING: INTER-COMPARING ON THE EFFICIENCY OF SCENARIOS OF AGRICULTURAL PRACTICES OPTIMIZATIONS AND LANDSCAPING.</td>
      <td>274</td>
    </tr>
    <tr>
      <td>UTILIZATION AND DISTRIBUTION OF ¹⁵N FROM FERTILIZERS TO COMPONENTS OF CEREAL - PEA MIXTURES</td>
      <td>275</td>
    </tr>
    <tr>
      <td>TEMPORAL FATE OF ¹⁵N FROM LEAF-LABELED WHITE AND RED CLOVER IN MIXTURE WITH GRASS</td>
      <td>277</td>
    </tr>
    <tr>
      <td>RECYCLING OF BIOGAS DIGESTATE IN AGRONOMIC PLANT PRODUCTION - NITROGEN FERTILIZER VALUE AND POSSIBLE NITRATE LEACHING.</td>
      <td>279</td>
    </tr>
    <tr>
      <td>DO CATCH CROPS IMPROVE NITROGEN USE EFFICIENCY OF SILAGE MAIZE?</td>
      <td>281</td>
    </tr>
    <tr>
      <td>N₂O FLUXES AND MINERAL N DYNAMICS FOLLOWING GRASSLAND RENEWAL TECHNIQUES AND GRASSLAND CONVERSION TO ARABLE LAND</td>
      <td>283</td>
    </tr>
    <tr>
      <td>EARLY SOWING ENHANCES GRAIN YIELDS AND N USE EFFICIENCY IN WINTER WHEAT</td>
      <td>285</td>
    </tr>
    <tr>
      <td>EFFECT OF APPLICATION AND NITRIFICATION INHIBITORS ON TRACE GAS FLUXES FROM A MAIZE FIELD AFTER CATTLE SLURRY AMENDMENT</td>
      <td>287</td>
    </tr>
    <tr>
      <td>N₂O EMISSIONS AFTER OILSEED RAPE RESIDUE INCORPORATION AS AFFECTED BY SOIL TILLAGE</td>
      <td>289</td>
    </tr>
    <tr>
      <td>LAND USE RELATED INTERVENTIONS ON THE NITROGEN CYCLE - A CASE STUDY OF THE UPPER ENNS VALLEY, A LONG-TERM SOCIO-ECONOMIC AND ECOSYSTEM RESEARCH REGION IN AUSTRIA</td>
      <td>291</td>
    </tr>
    <tr>
      <td>SOIL NITROUS OXIDE (N₂O) EMISSIONS IN SPRINKLER CORN (ZEA MAYS L.): INFLUENCE OF IRRIGATION TIME AND FREQUENCY.</td>
      <td>293</td>
    </tr>
    <tr>
      <td>QUANTIFICATION OF N-RHIZODEPOSITION OF PEAS UNDER FIELD CONDITIONS</td>
      <td>295</td>
    </tr>
    <tr>
      <td>REMOTELY SENSING-BASED ANNUAL NITROGEN BALANCE FORECAST AT FIELD SCALE FOR WINTER WHEAT, POTATO AND MAIZE CROPS IN BELGIUM</td>
      <td>297</td>
    </tr>
    <tr>
      <td>POTENTIAL FOR MITIGATING ATMOSPHERIC AMMONIA IN CANADA</td>
      <td>299</td>
    </tr>
    <tr>
      <td>USING BAYESIAN HIERARCHICAL MODELS TO BETTER UNDERSTAND AGRICULTURAL NITRATE CONTRIBUTION TO RIVER WATER</td>
      <td>301</td>
    </tr>
    <tr>
      <td>SENSITIVITY ANALYSIS OF NITIRSOIL MODEL OUTPUTS: SOIL MINERAL NITROGEN, NITROGEN LEACHING LOSSES AND NITROGEN CROP UPTAKE</td>
      <td>303</td>
    </tr>
    <tr>
      <td>EFFECT OF DIFFERENT N-MANAGEMENT MEASURES TO REDUCE N SURPLUSES ON N₂O EMISSIONS FROM VEGETABLE PRODUCTION</td>
      <td>305</td>
    </tr>
    <tr>
      <td>SOIL N AVAILABILITY PATTERN ON HORTICULTURAL LAND</td>
      <td>308</td>
    </tr>
    <tr>
      <td>N YIELD-SCALED EMISSIONS AND GREENHOUSE GAS INTENSITY FROM FORAGE MAIZE IN RELATION TO ADDITION OF 3,4 DIMETHYLPYRAZOLE PHOSPHATE TO CATTLE SLURRY AND MINERAL FERTILIZERS</td>
      <td>310</td>
    </tr>
    <tr>
      <td>NITROGEN-FERTILIZATION EFFECT ON N₂O EMISSION FROM A TYPICAL RUBBER PLANTATION</td>
      <td>312</td>
    </tr>
    <tr>
      <td>POTENTIAL INHIBITOR EFFECT OF HIPPURIC ACID ON NITROUS OXIDE EMISSIONS FROM GRASSLAND ON A HEAVY CLAY SOIL</td>
      <td>315</td>
    </tr>
    <tr>
      <td>NITRATE LEACHING UNDER WINTER OILSEED RAPE AS AFFECTED BY SOWING DATE AND EARLY INCORPORATION OF SLURRY</td>
      <td>317</td>
    </tr>
  </tbody>
</table>
<table>
  <tbody>
    <tr>
      <td>DEVELOPING 'N-CIRCLE': A PRIORITISED AGENDA TOWARDS 'CLOSED-LOOP' AGRICULTURAL NITROGEN CYCLING FOR CHINA AND EUROPE</td>
      <td>319</td>
    </tr>
    <tr>
      <td>CHARACTERISTICS OF NITROGEN BALANCE IN OPEN-AIR AND GREENHOUSE VEGETABLE CROPPING SYSTEMS OF CHINA</td>
      <td>322</td>
    </tr>
    <tr>
      <td>DISSIMILATORY NITRATE REDUCTION PROCESSES AND THEIR CONTRIBUTION TO NITROGEN LOSS IN CHINESE PADDY SOILS</td>
      <td>324</td>
    </tr>
    <tr>
      <td>MORE BENEFIT FROM COVER CROPS BY HARVESTING</td>
      <td>326</td>
    </tr>
    <tr>
      <td>ORGANIC VERSUS CONVENTIONAL- CAN A<sup>15</sup>N BE USED AS AN INDICATING PARAMETER IN GARLIC, SWEET PEPPER AND CARROT?</td>
      <td>328</td>
    </tr>
    <tr>
      <td>PLANT AND MICROBIAL BIOMASS, NITROUS OXIDE AND CARBON DIOXIDE EMISSIONS IN INTENSIVELY MANAGED PERMANENT GRASSLAND UNDER CONTROLLED CONDITIONS AS AFFECTED BY NITROGEN LEVEL</td>
      <td>330</td>
    </tr>
    <tr>
      <td>GLOBAL AYALYSIS OF LIVESTOCK PRODUCTION AND NUTRIENT BALANCES</td>
      <td>332</td>
    </tr>
    <tr>
      <td>SOIL MINERAL NITROGEN CONTENT AND NITROGEN UPTAKE BY CROPS AFTER THE USE OF DIFFERENT ORGANIC FERTILIZERS</td>
      <td>333</td>
    </tr>
    <tr>
      <td>USE OF SOIL ECA MEASUREMENT FOR EVALUATING SOIL SPATIAL VARIABILITY FOR NITROGEN MANAGEMENT IN SUPER-INTENSIVE OLIVE OIL TREE ORCHARDS</td>
      <td>335</td>
    </tr>
    <tr>
      <td>MODELLING THE EFFECT OF POST-HARVEST MANAGEMENT MEASURES ON NITRATE LEACHING DURING AUTUMN AND WINTER</td>
      <td>337</td>
    </tr>
    <tr>
      <td>NITROGEN APPLICATION OF ORGANIC FERTILIZER IN TIMOTHY (PHLEUM PRATENSE L.) SEED PRODUCTION</td>
      <td>339</td>
    </tr>
    <tr>
      <td>ASSESSING MICROBIAL ACTIVITY IN DIGESTATE-FERTILIZED CROPS WITH FERTIMETRO: A PATENTED DEVICE EXPLOITING BURIED COTTON THREAD BAITS TO OPTIMIZE N AND P FERTILIZATION</td>
      <td>341</td>
    </tr>
    <tr>
      <td>ASSESSMENT OF ECOSYSTEM SERVICES RENDERED BY AGROMINING OF NICKELIFEROUS SOILS: ASSOCIATION OF LEGUMINOUS AND HYPERACCUMULATOR?</td>
      <td>343</td>
    </tr>
    <tr>
      <td>DOES BIOCHAR REDUCE AMMONIA EMISSIONS FROM DIFFERENT AMENDMENTS TO AGRICULTURAL SOILS?</td>
      <td>345</td>
    </tr>
    <tr>
      <td>N<sub>2</sub>O FLUXES FROM AN AGRICULTURAL SOIL IN GERMANY DURING A COMPLETE CROP ROTATION: UNCERTAINTIES, ENVIRONMENTAL INSIGHTS AND MODEL PERFORMANCE</td>
      <td>347</td>
    </tr>
    <tr>
      <td>INTERNATIONAL TRADE OF ANIMAL FEED AND DECOUPLING OF NITROGEN AND PHOSPHORUS CYCLING IN CROP AND ANIMAL PRODUCTION; CASE-STUDIES OF ELEVEN COUNTRIES</td>
      <td>349</td>
    </tr>
    <tr>
      <td>ARABLE MAIZE FOLLOWING PERMANENT GRASSLAND - IMPACT OF TILLAGE ON GREENHOUSEGAS-EMISSIONS, CARBON-BALANCE AND NITRATE-LEACHING</td>
      <td>351</td>
    </tr>
    <tr>
      <td>EVALUATION OF THE SUB-GRID VARIABILITY OF MODELS SIMULATING ATMOSPHERIC NITROGEN FLUXES AT THE REGIONAL SCALE FROM MODELS INTEGRATING PROCESSES AT THE LANDSCAPE SCALE</td>
      <td>353</td>
    </tr>
    <tr>
      <td>ANAEROBIC DIGESTION OF ORGANIC MANURES AND EFFECTS ON NITRATE LEACHING ESTIMATED UNDER DANISH CONDITIONS</td>
      <td>355</td>
    </tr>
    <tr>
      <td>THE EFFECTS OF SOIL TYPE AND CAULIFLOWER CROP RESIDUE PLACEMENT ON NITROUS OXIDE AND AMMONIA EMISSIONS</td>
      <td>357</td>
    </tr>
  </tbody>
</table>
<table>
  <tbody>
    <tr>
      <td>LOW USE OF NITROGEN IN THE COLUMBIAN INDUSTRY OF SUBSTRATE GROWN CUT FLOWERS</td>
      <td>359</td>
    </tr>
    <tr>
      <td>EFFECT OF WOOD ASH AND ROCKDUST ON CLOVER GROWTH AND DINITROGEN FIXATION</td>
      <td>361</td>
    </tr>
    <tr>
      <td>GUIDING FARMERS TOWARDS SMART FERTILIZATION AND A BETTER SOIL QUALITY IN BELGIUM AND THE NETHERLANDS</td>
      <td>363</td>
    </tr>
    <tr>
      <td>PARAMETRIC CONSTRAINTS ACROSS PROCESS-BASED MODELS IN SIMULATING NITROUS OXIDE EMISSIONS FROM ARABLE FIELDS</td>
      <td>366</td>
    </tr>
    <tr>
      <td>SIMULATING SUSTAINABLE NITROGEN AND PHOSPORUS USE ON FARM LEVEL IN ACCORDANCE TO FERTILISING LIMITS IN FLANDERS</td>
      <td>368</td>
    </tr>
    <tr>
      <td>NITROGEN LEACHING OF AUSTRIAN'S ARABLE AREAS UNDER THE PERSPECTIVE OF GREENHOUSE GASES EMISSIONS</td>
      <td>370</td>
    </tr>
    <tr>
      <td>OPTIMIZING N-TRANSFER IN WINTER-WHEAT CROPPING SYSTEMS THROUGH MICROBIAL N-IMMOBILIZATION</td>
      <td>372</td>
    </tr>
    <tr>
      <td>EFFECT OF A NITRIFICATION INHIBITOR ON NITROUS OXIDE AND AMMONIA EMISSIONS FROM A MAIZE CROP</td>
      <td>373</td>
    </tr>
    <tr>
      <td>NITROGEN MINERALISATION AND GREENHOUSE GAS EMISSION FROM SOIL APPLICATION OF SLUDGE FROM SLUDGE TREATMENT REED BED SYSTEMS</td>
      <td>375</td>
    </tr>
    <tr>
      <td>A PROPOSAL OF NITROGEN BALANCE IN A HIGH DENSITY OLIVE ORCHARD.</td>
      <td>377</td>
    </tr>
    <tr>
      <td>AMMONIA AND GHG EMISSIONS IN FRESH DIGESTATE LAGOONS IN SPAIN: A COMPARATIVE ASSESSMENT BETWEEN COVERED AND UNCOVERED STORAGE</td>
      <td>379</td>
    </tr>
    <tr>
      <td>WINTER COVER CROPS IMPACT ON PLANT NUTRIENTS IN AN ORGANIC CROP ROTATION</td>
      <td>382</td>
    </tr>
    <tr>
      <td>MONITORING FERTILIZATION EFFECTS ON GROUNDWATER NITRATE POLLUTION</td>
      <td>384</td>
    </tr>
    <tr>
      <td>EFFECT OF COVER CROP BIOMASS APPLICATION AS A GREEN MANURE ON REDUCING NITROUS OXIDE EMISSION</td>
      <td>386</td>
    </tr>
    <tr>
      <td>DIAGNOSIS OF N LOSSES IN CROPPING SYSTEMS IN WATER PROTECTION AREAS</td>
      <td>387</td>
    </tr>
    <tr>
      <td>MANAGEMENT PRACTICES OF MISCANTHUS × GIGANTEUS STRONGLY INFLUENCE SOIL PROPERTIES AND N₂O EMISSIONS</td>
      <td>389</td>
    </tr>
    <tr>
      <td>IMPLEMENTATION OF NITROGEN DYNAMICS IN THE DECISION SUPPORT SYSTEM ÖKO-SIMPHYT TO IMPROVE MANAGEMENT PROCESSES IN ORGANIC POTATOES</td>
      <td>391</td>
    </tr>
    <tr>
      <td>AMMONIA EMISSION FROM TWO LAYING HEN FACILITIES DIFFERING ON MANURE AND VENTILATION MANAGEMENT.</td>
      <td>393</td>
    </tr>
    <tr>
      <td>COMPARISON OF NITROUS OXIDE EMISSION FACTORS FROM COVER CROP BIOMASS AMENDED UPLAND AND PADDY SOILS DURING CROPPING PERIODS</td>
      <td>395</td>
    </tr>
    <tr>
      <td>NITROUS OXIDE AND NITRATE LOSSES - INFLUENCING FACTORS IN WILLOW CROPPING INVESTIGATED BY MODELLING</td>
      <td>396</td>
    </tr>
    <tr>
      <td>A NETWORK TO MEASURE AND ANALYZE VARIABILITY IN SOIL NITROGEN MINERALIZATION AT THE FIELD SCALE IN BRITTANY (FRANCE)</td>
      <td>398</td>
    </tr>
    <tr>
      <td>SOIL NITROGEN MINERALIZATION: RELIABILITY OF A MULTI-COMPONENT APPROACH</td>
      <td>400</td>
    </tr>
    <tr>
      <td>CROPPING SEQUENCE AFFECTS NITRATE LEACHING DIFFERENTLY ON SANDY SOILS IN THE NETHERLANDS</td>
      <td>402</td>
    </tr>
  </tbody>
</table>
<table>
  <tbody>
    <tr>
      <td>A NOVEL COMBINATION OF UREASE INHIBITORS AND ITS FORMULATION WITH BETTER PERFORMANCE CONCERNING BIOLOGY, HANDLING TRANSPORT AND STORAGE COMPARED TO EXISTING PRODUCTS</td>
      <td>404</td>
    </tr>
    <tr>
      <td>COUPLING OF DAYCENT AND HYDRUS FOR STUDING THE WATER AND NITROGEN CYCLES IN SOILS WITH SHALLOW GROUNDWATER - A CASE STUDY IN NORTH ITALY</td>
      <td>406</td>
    </tr>
    <tr>
      <td>THE APPORTIONING OF N<sub>2</sub>O EMISSIONS TO NITRIFICATION OR DENITRIFICATION FROM DIFFERENT NITRATE SOURCES AT DIFFERENT WATER-FILLED-PORESPACES (WFPS)</td>
      <td>408</td>
    </tr>
    <tr>
      <td>FOCUS ON NUTRIENTS - A SWEDISH EXTENSION SERVICES PROGRAM</td>
      <td>410</td>
    </tr>
    <tr>
      <td>DIFFERENT NITROGEN SEASONAL DYNAMIC UNDER CONVENTIONAL AND CONSERVATION TILLAGE</td>
      <td>412</td>
    </tr>
    <tr>
      <td>TOP DRESSING NITROGEN RECOMMENDATION IN WHEAT AFTER APPLYING ORGANIC MANURES. USE OF FIELD DIAGNOSTIC TOOLS</td>
      <td>414</td>
    </tr>
    <tr>
      <td>CROPPING SYSTEMS FOR TRANSFER OF SOIL MINERAL N IN ORGANIC GREEN MANURE LEYS TO SUBSEQUENT SPRING WHEAT</td>
      <td>416</td>
    </tr>
    <tr>
      <td>EFFECT OF VARYING DOSES OF SOIL APPLIED UREA ON GROWTH AND PRODUCTION POTENTIAL OF QUINOA (CHENOPODIUM QUINOA WILLD.)</td>
      <td>418</td>
    </tr>
    <tr>
      <td>NITROGEN LEACHING RISK FROM PREFERENTIAL FLOW IN A STONY SOIL IRRIGATED BY CENTRE PIVOT</td>
      <td>420</td>
    </tr>
    <tr>
      <td>REYGRASS OVERSOWING IN SOYBEAN AS AN ALTERNATIVE TO REDUCE NITROUS OXIDE EMISSIONS IN INTEGRATED CROP-LIVESTOCK SYSTEM</td>
      <td>422</td>
    </tr>
    <tr>
      <td>EFFECT OF N SOURCE ON GROWTH, YIELD, YIELD COMPONENTS AND YIELD OF BUCKWHEAT IN THE FENUGREEK/BUCKWHEAT INTERCROPPING</td>
      <td>424</td>
    </tr>
    <tr>
      <td>CONSIDERING THE FINE SCALE OF VARIATION FOR NITROGEN MANAGEMENT</td>
      <td>426</td>
    </tr>
    <tr>
      <td>QUANTIFICATION OF LABILE NITROGEN IN SOIL UNDER DIFFERENT FERTILIZATION REGIMES</td>
      <td>428</td>
    </tr>
    <tr>
      <td>NITROGEN FERTILIZATION REDUCTION OF CORN IN A NITRATE VULNERABLE ZONE</td>
      <td>430</td>
    </tr>
    <tr>
      <td>OPTIMIZATION TESTING AND SPLITTING OF THE CONTRIBUTION PERIOD OF NITROGEN FOR GROWING DURUM WHEAT IN IRRIGATED SEMI-ARID ZONE</td>
      <td>432</td>
    </tr>
    <tr>
      <td>NITROGEN BALANCES AND FLOWS IN CENTRAL SPAIN DAIRY FARMS</td>
      <td>434</td>
    </tr>
    <tr>
      <td>NITROUS OXIDE EMISSIONS FROM A SUGARCANE CROP UNDER DIFFERENT NITROGEN FERTILIZER RATES</td>
      <td>436</td>
    </tr>
    <tr>
      <td>APPARENT LONG-TERM FERTILIZER REPLACEMENT VALUE OF ORGANIC AMENDMENTS DEPENDS ON MINERAL FERTILIZER N RANGE ITSELF</td>
      <td>438</td>
    </tr>
    <tr>
      <td>ESTIMATION OF THE QUANTITY OF N2 FIXED BY CLOVER GROWN IN THE MIXTURE WITH GRASS IN LONG TERM FIELD EXPERIMENT</td>
      <td>441</td>
    </tr>
    <tr>
      <td>NITRIFICATION INHIBITION BY PEAT ENRICHED WITH NANOPARTICLES OF SILICATE MINERALS</td>
      <td>443</td>
    </tr>
    <tr>
      <td>NITROGEN BALANCES IN FIELD EXPERIMENTS, FARMS AND REGIONS</td>
      <td>445</td>
    </tr>
    <tr>
      <td>ESTIMATING THE NITROGEN FERTILIZER REQUIREMENTS OF HIGH- YIELDING HYBRID GRAIN CORN VARIETIES</td>
      <td>447</td>
    </tr>
    <tr>
      <td>NITROGEN LOSSES FROM AUSTRIAN AGRICULTURAL SOILS - USE OF MODEL RESULTS FOR THE GREENHOUSE GAS INVENTORY</td>
      <td>449</td>
    </tr>
  </tbody>
</table>
NITROGEN DYNAMICS AND N-CYCLING BACTERIAL COMMUNITIES IN A MEDITERRANEAN OLIVE ORCHARD UNDER A SUSTAINABLE FARMING SYSTEM 451

NITROUS OXIDE AND NITRATE LOSSES - INFLUENCING FACTORS IN WILLOW CROPPING INVESTIGATED BY MODELLING 453

HOW DOES GRAZING ABANDONMENT AFFECT SOIL MICROBIAL ACTIVITY AND AMINO ACID UTILIZATION? 455

DYNAMIC OF SOIL O₂ AFFECTS N₂O PRODUCTION PATHWAYS AFTER APPLICATION OF CATTLE SLURRY AND DMPP NITRIFICATION INHIBITOR 457

UK-CHINA VIRTUAL JOINT CENTRE FOR IMPROVED NITROGEN AGRONOMY 459

CALIBRATION OF A SIMPLE MECHANISTIC WHEAT MODEL FOR WITHIN-FILED VARIABLE N APPLICATION 461
# SIMULATING N₂O EMISSIONS USING THE STICS SOIL-CROP MODEL IN LOW-INPUT CROPPING SYSTEMS IN SW FRANCE

Daniel Plaza-Bonilla¹,², Joël Leonard³, Céline Peyrard³, Pierre Perrin¹, Bruno Mary³, Éric Justes¹

¹INRA, UMR-AGIR, 31326 Castanet-Tolosan, France, ²Departamento de Suelo y Agua. Estación Experimental de Aula Dei (EEAD-CSIC), 50056 Zaragoza, Spain, ³INRA, UR AgroImpact, 02000 Barenton-Bugny, France

## Objectives

Nitrous oxide (N₂O) is a powerful greenhouse gas (GHG) with a global warming potential 265 times greater than carbon dioxide (CO₂), making agriculture a major actor in the emission of this GHG [1]. The use of models is a key strategy for evaluating N₂O emissions from different cropping systems at different scales, given their capacity to integrate the processes that regulate N₂O emission [2]. In this work we tested the ability of the soil-crop model STICS, able to deal with complex rotations, to simulate the emissions of N₂O in low-input cropping systems.

## Method

The performance of the model STICS v.8 to simulate N₂O emissions was evaluated using observed data of the MicMac experiment testing innovative low input cropping systems (Auzeville, SW France). In that experiment, 3-year alternatives to the traditional durum wheat-sunflower rotation were compared for decreasing N fertilizer and pesticide inputs. For each 3-yr rotation, N₂O emissions were measured using automatic chambers (0.70 x 0.70 x 0.30 m, 3 replicates). N₂O concentration was quantified using automatic chambers. Other key variables were also measured (e.g. soil water and mineral N contents, soil temperature, and bulk density). Plant and soil input parameters of the model were calibrated and validated as reported by [3].

## Results

Our preliminary results show a fairly good capacity of the STICS model to simulate N₂O emissions from the soil to the atmosphere, in different cash crop and cover crop phases of a rotation in a low-input cropping system. Basically, STICS simulates emissions of the same data range than the observed values and seems able to capture the main trends of emissions. However, our first work shows that some aspects remain to be improved. Firstly, the model seems to be too sensitive to N fertilizer application, simulating some N₂O peaks that were not observed under field conditions with dry soil surface. Secondly, the model is highly sensitive to soil bulk density. In its current status, STICS takes soil bulk density – and concomitantly, porosity – as a static soil property during the crop cycle, fact that hinders the ability to mimic the dynamic soil structure measured under field conditions. Observed and simulated N₂O peaks showed the same order of magnitude, although with a short delay which highlights the need to improve the simulation of temporal dynamics of porosity and gas diffusion within soil structure [2], [4].

## Conclusions

Our preliminary results show the potential of the STICS soil-crop model to simulate the range of values of N₂O emissions of such complex crop rotations with cover crops without great time investments in calibration, which is satisfactory. However, some formalisms and parameterization still need to improve the dynamic of emissions and obtain more precise estimations of the impact of agricultural management practices and cropping systems on N₂O emissions.

## Acknowledgements

This research was supported by the French ANR-09-STRA-06 (MicMac project). The French Ministry of Agriculture funded the CASDAR Leg-N-GES project coordinated by Jean-Pierre Cohan (Arvalis Institut du Vegetal).
## References

[1] IPCC. 2013. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change. Climate Change 2013: The Physical Science Basis. Cambridge University Press, Cambridge, United Kingdom and New York NY, USA.

[2] Doltra, J., J.E. Olesen, D. Báez, A. Louro and N. Chirinda. 2015. European Journal of Agronomy 66, 8-20.

[3] Plaza-Bonilla, D., J.M. Nolot, D. Raffaillac and E. Justes. 2015. Agriculture, Ecosystems and Environment 212, 1-12.

[4] Blagodatsky, S and P. Smith. 2012. Soil Biology and Biochemistry 47, 78-92.
# AMMONIA EMISSIONS FROM TWO NATURALLY VENTILATED CATTLE BUILDINGS IN IRELAND

William Burchill¹, Tom Misselbrook², Gary Lanigan¹

¹Teagasc, Crops, Environment & Land Use Programme, Teagasc, Johnstown Castle Environment Research Centre, Co. Wexford, Ireland, ²Rothamsted Research - North Wyke, Okehampton, Devon, EX20 2SB, UK

## Objectives

Ammonia ($NH_3$) gas emission represents a substantial economic loss of nitrogen for farmers and is also environmentally detrimental. Agriculture contributes 98% of the total $NH_3$ emissions in Ireland with 48% of agricultural emissions coming from animal housing and slurry storage which are estimated to arise. However, current $NH_3$ emission estimates for Irish cattle housing are based on UK derived emission factors. There is a need to create country specific emissions factors to improve the accuracy of Ireland's $NH_3$ emission inventory. In particular, there is a lack of data relating to cattle buildings with slatted floors, as the UK studies have primarily focused on solid floor cubicle and straw bedded cattle buildings. The objective of this study therefore was to quantify $NH_3$ emissions and emission factors from two cattle buildings with solely slatted floors in Ireland.

## Method

This study was conducted on two commercial livestock farms (building “A” and “B”) in the south of Ireland. The two buildings consisted of a solid floor feeding alleyway with slatted floor pens on either side of the feeding alleyway. Both buildings were roofed with a combination of concrete and Yorkshire boarding perimeter walls. The external dimensions of building A were 19.1 m × 13.2 m with a roof height of 5.5m. The external dimensions of building B were 14.4 m × 12.9 m with a roof height of 4.7 m. Building A contained, on average, 41 livestock units (lu: 1 livestock unit = 500 kg liveweight) during the measurements, while building B contained 31 lu. The livestock were a mixture of suckler cows, dairy heifers (6-12 mths) and suckler weanlings (6-12 mths). The diet of the livestock primarily consisted of grass silage with small amounts of straw and mixed rations.

Measurements were conducted on each building on seven occasions over two consecutive winters (Nov to March: 2015 and 2016). Ammonia emission measurements for both buildings were made using passive flux samplers (Ferm tubes) [1]. Samplers were distributed evenly across the building openings and contained two $NH_3$ acid traps which captured $NH_3$ as it entered and exited the buildings. Samplers were exposed on the buildings for 24 h for each measurement. Following exposure, the amount of $NH_3$ collected in each acid trap was determined by extracting with deionised water over 16 h, followed by analysis for ammonium. The net flux from the buildings (kg $NH_3$-N lu⁻¹ d⁻¹) was calculated as described by Pereira *et al.* (2010) [2].

Ammonia emissions factors (g $NH_3$-N lu⁻¹ d⁻¹) were calculated by dividing the daily fluxes by the number of livestock units in the building on each measurement day. The emission factor as a percentage of total N excreted was calculated using standard values of N excretion for different livestock categories (S.I No. 31 of 2014). Climatic data such as air temperature, wind speed and wind direction were recorded during each measurement inside and outside the buildings.

## Results

Daily $NH_3$ emissions varied over time in both buildings. Mean emissions (kg $NH_3$-N d⁻¹) were 1.49 from building A and ranged from 0.52 to 2.52. Daily emissions (kg $NH_3$-N d⁻¹) from building B were four-fold lower than building A with a mean of 0.35 and ranged from 0.06 to 0.63. The larger livestock numbers (generating more urine and dung) and greater emitting surface area associated with the larger building was the most likely cause for the higher emissions from building A. The emissions from each side and the roof of the buildings were not uniform. In building A the largest contributor was the east side (56%) followed by the north side (16%), west side (15%), south side (7%) and roof (6%). The high proportion of emissions form
the east side of the building was due to the westerly wind directions experienced during these measurements, with is typical of Ireland's climate. Building B was slightly different to building A with the largest contributor being the east side (31%) followed by the south side (24%), west side (16%), north side (15%) and roof (14%). The wind direction was much more variable during the measurements on building B, which resulted in less dominance of the east and north side of the building.

The NH₃ emission factors (g NH₃-N lu⁻¹ d⁻¹) varied over time and between buildings and ranged from 13.4 to 54.3 on building A (mean: 34.0, S.D.: 15.7) and from 1.8 to 18.4 on building B (mean: 11.2, S.D.: 5.8). The overall mean emission factor from the study was 22.5 g NH₃-N lu⁻¹ d⁻¹ or 12.8% of total N excreted. This was somewhat lower than the mean emission factors (34.3 g NH₃-N lu⁻¹ d⁻¹) reported for buildings with cubicles and scraped alleyways but similar to those reported for straw-bedded buildings (23.1 g NH₃-N lu⁻¹ d⁻¹) in the UK [3]. Total ammonium N is assumed to account for 60% of total N excreted in the calculations used in Ireland national NH₃ inventory. Using the same assumption the results of this study suggests an overall emissions factor of 21.4% of TAN excreted in this study. It is also lower than the currently applied emission factor of 32% of TAN excreted indoors in the Irish NH₃ inventory.

## Conclusions

The results of this study represent the first direct measurements of NH₃ emissions from cattle buildings in Ireland, which can be used as a starting point in the generation of robust country specific emissions factors to improve Ireland's national NH₃ inventory. The overall mean emission factor from the study was 22.5 g NH₃-N lu⁻¹ d⁻¹, which is lower than the currently used emission factor for Ireland. The results of this study also add to the limited available datasets on NH₃ emissions from cattle buildings with solely slatted floors.

## Acknowledgements

This work was funded by the Irish Department of Agriculture, Food and the Marine. The authors thank Ms Francesca Reville, Ms Sinead Breen and internship students for assistance with field sampling.

## References

[1] Scholtens, R., Dore, C.J., Jones, B.M.R., Lee, D.S., Phillips, V.R., 2004. Measuring ammonia emission rates from livestock buildings and manure stores-part 1: development and validation of external tracer ratio, internal tracer ratio and passive flux sampling methods. Atmospheric Environment 38, 3003-3015.

[2] Pereira, J., Misselbrook, T.H., Chadwick, D.R., Coutinho, J., Trindade, H., 2010. Ammonia emissions from naturally ventilated dairy cattle buildings and outdoor concrete yards in Portugal. Atmospheric Environment 44, 3413-3421.

[3] Misselbrook, T.H., Gilhespy, S.L., Cardenas, L.M., Williams, J., Dragosits, U., 2015. Inventory of ammonia emissions from UK agriculture, 2014. Inventory submission report to Defra as part of project SCF0102.
# Ammonia and Nitrous Oxide Losses from Mechanically Turned Cattle Manure Windrows: a Regional Composting Network

Haritz Arriaga, Maialen Viguria, Diana M. López, Oier Alberdi, Pilar Merino

NEIKER-Tecnalia, Derio, the Basque Country, Spain

## Objectives

A cattle manure composting network exists in the Basque Country (northern Spain), in which solid manure produced by 82 farmers is composted at farm level. All compost windrows are mechanically turned according to a previously agreed calendar and the end product is sold to regional crop producers. This network let farmers reduce on-farm waste volume whereas regional nutrient surplus is balanced. Despite these benefits, manure composting is related to N gaseous losses into the atmosphere. Ammonia ($NH_3$) is usually lost within the first month after the heap establishment. Nitrous oxide ($N_2O$) losses occur during the mesophilic phase of the process. The objective was to assess $NH_3$ and $N_2O$ emissions from turned cattle manure composts windrows, which were managed in “real-life” conditions and differed in their origin (deep litter and solid fraction) and maturity (fresh and mature piles).

## Method

Gaseous N losses ($NH_3$ and $N_2O$) were monitored from 4 windrows before and after 1 to 3 turning operations in spring/summer 2012. Three deep litter derived piles were studied at 2 cattle farms (beef and dairy). Cereal straw was used as bedding material ($8 \text{ kg cow}^{-1} \text{ d}^{-1}$) in all cases. The windrow heaped at beef cattle farm (BDL) had been established outdoors in December 2011. Windrows with different maturities had been heaped at dairy farm: $DDL_m$ in December 2011 and $DDL_f$ in March 2012. All windrows showed a similar shape (115 m length, 3 m width and 1.3 m height). The fourth windrow (SMS), which was obtained after solid-liquid slurry separation, had been heaped in a second dairy cattle farm. The solid fraction had progressively been heaped in 3 windrows from March 2012 onwards (30 m length, 3 m width and 1 m height). BDL, $DDL_m$, $DDL_f$ and SMS windrows were mechanically turned by a self-propelled turner (4300SP Menart). The first turning in BDL, $DDL_m$ and $DDL_f$ was conducted in 13th April 2012, whereas the second turning was performed in 17th May 2012. Finally, the third turning, which was monitored in SMS, was conducted in 10th August 2012.

Ammonia emissions were measured by the open chamber technique [1]. Three PVC chambers (6.75 L) were randomly placed on all the piles. Measurements were conducted during 5 days after the windrow turnings. Chambers were daily repositioned for representing the spatial variation. Ammonia measurements were monitored from 10.00h to 15.00h by a photoacoustic analyser (Bruel & Kjaer 1302). Nitrous oxide was measured by the closed chambers technique [2]. Sampling was daily performed during 1 week after the turning operations and twice per week during the rest of the experimental period. Four PVC chambers (20 cm diameter, 15 cm height) were inserted in each windrow. Gas samples were taken 0, 20 and 50 min after the chamber closure and introduced in GC vials. Nitrous oxide concentration was quantified by GC (Agilent 7890A). Finally, all the windrows were analyzed for total N (TN) and ammonium-N ($NH_4^+$-N). Atmospheric and windrow temperatures were also monitored.

## Results

Negligible $NH_3$ losses were monitored before the first mechanical turning in BDL, $DDL_m$ and $DDL_f$, and the third turning in SMS windrows. These results agreed with previously reported data [3], in which $NH_3$ was mostly emitted within the first 2 weeks after heaping the windrows. The maturity of BDL, $DDL_m$ and $DDL_f$ and SMS heaps (> 1 month) would have limited $NH_3$ losses. The low $NH_4^+$-N pool in all the windrows (< 5% TN) suggested that N immobilization was held by the microbial flora. The effect of the mechanical turnings was not uniform on $NH_3$ emission pattern. Emission was not affected by the first turning in BDL, $DDL_m$ and $DDL_f$ composts, while it was released at low levels after the second turning in BDL and $DDL_f$ (< 2.0 mg m$^{-2}$ d$^{-1}$). This effect could be related to the warmer atmospheric conditions during the second turning oper-
ations (≈ 20°C). Atmospheric temperature was around 10°C during the first turning works. A similar mean
NH₃ peak was observed in SMS windrow after the third turning process in August 2012 (atmospheric tem-
perature > 20°C). All these results agreed with the available literature, which showed that turning of mature
composts had little effect on NH₃ volatilization [3]. According to the best management practices in the re-
gion, the first turning operations should have been conducted in January 2012 for BDL and DDLm. However,
the adverse weather conditions in winter delayed the field works.

In relation N₂O losses, low mean emission rates were recorded in all the heaps during the monitoring period (< 50 mg m⁻² d⁻¹). This emission rate was close to data reported in the literature for mature manure-derived piles [3]. Above mentioned N immobilization would have contributed to the low N₂O emissions. Nitrous oxide emission increased significantly after the turning works, especially in DDLf and SMS with 253.0 and 326.8 mg m⁻² d⁻¹, respectively. These peaks were observed 3 days after the second and third turning works in DDLf and SMS (windrow temperature, 30-40°C), respectively. This delay would support that N₂O losses from turned windrows arise due to microbial activities rather than the physical turning. The lack of response of BDL and DDLm was attributed to windrow temperatures below 20°C.

Conclusions

The present study concluded that two turning operations in mature compost windrows have not significant
effect on NH₃ and N₂O losses. An additional third turning, which is required for well-humificated composts,
may be a suitable option in mature windrows without increasing significantly NH₃ and N₂O losses. In con-
trast to the performance of gaseous losses in experimental systems, losses from “real-life” manure compost-
ing- turning networks are dependent on (i) the manure management practices at farm level (e.g. heaping
compost windrows in winter instead of in warmer seasons); and (ii) regional climatic conditions (e.g. alter-
ing theoretically best management practices for turning during the composting process).

Acknowledgements

This work was funded by the Spanish National Institute for Agronomic Research (RTA2011-00107) and the
European Regional Development Fund (ERDF). Oier Alberdi holds a grant from Agriculture Department of
Basque Government.

References

[1] Merino, P., Arriaga, H., Salcedo, G., Pinto, M., Calsamiglia, S. 2008. Agriculture Ecosystems and Envi-
ronment 123, 88-94.

[2] Merino, P., Estavillo, J.M., Pinto, M., Rodríguez, M., Duñabeitia, M.K., González-Murua, C. 2001. Soil Use and Management 17, 121-127.

[3] Parkinson, R., Gibbs, P., Burchett, S., Misselbrook, T. 2004. Bioresource Technology 91, 171-178.
# Further development and appraisal of the Geological Survey of Ireland's Potentially Denitrifying Bedrock map

Katie Tedd⁴, Natalya Hunter Williams¹, Catherine Coxon², Coran Kelly³, Shane Carey⁴, Damien Doherty⁴, Natalie Duncan⁴, Sara Raymond⁴

¹Geological Survey of Ireland, Dublin, Ireland, ²Trinity College Dublin, Dublin, Ireland, ³Tobin Consulting Engineers, Dublin, Ireland, ⁴Independent Geoscientist, Dublin, Ireland

## Objectives

Eutrophication is the principal threat to surface water quality in Ireland. In some situations, groundwater represents a significant pathway for nutrient transport to surface water. Nitrate is usually the principal limiting nutrient responsible for eutrophication in estuarine and coastal waters [1]. In addition, groundwater plays a role in indirect greenhouse gas emissions, transferring dissolved nitrogen from terrestrial ecosystems to the atmosphere via the aquatic pathway [2].

The Geological Survey of Ireland (GSI) developed a Potentially Denitrifying Bedrock map [3] to allow the Environment Protection Agency (EPA) and other decision makers to better assess the risk of surface water eutrophication from groundwater sources [4] as part of the implementation of the E.U. Water Framework Directive (WFD) (2008/98/EC).

This study aims to appraise and to further develop the GSI's Potentially Denitrifying Bedrock map in order to improve estimates of nitrate fluxes from groundwater to surface waters.

## Method

In certain hydrogeological settings in Ireland, denitrification can occur. Denitrification reduces nitrate to nitrogen gas, or where the process is incomplete, the greenhouse gas nitrous oxide may be released. The GSI's Potentially Denitrifying Bedrock map [3] focuses on the denitrification of nitrate which occurs in the bedrock making use of electron donors present within the bedrock. This is in contrast to denitrification occurring in the subsoils and shallow groundwater which has been shown to be significant in some settings in Ireland [5].

The GSI's Potentially Denitrifying Bedrock map identifies bedrock units which are likely to contain electron donors such as organic carbon or metal sulphides (e.g. pyrite). Data for the map came from a number of sources: (i) the descriptions of the bedrock units from the published GSI 1:100,000 scale bedrock maps (GSI, various); (ii) evaluations of the GSI's draft Aggregate Potential maps [6]; (iii) hydrogeological field experience of pyrite occurrence or hydrogen sulphide containing groundwater; (iv) geological knowledge of experienced geologists; and (v) other knowledge of pyrite occurrence. These data sources were combined to produce a Geographical Information System Potentially Denitrifying Bedrock map. The new version of the map, currently under development, will benefit from updated GSI bedrock and aggregate potential mapping; as well as recent research results, such as [5], [7] and [8].

Groundwater nitrate data have been collected in Ireland since the 1970s. Typically, measurements in the 1970s and 1980s were conducted during the course of different projects implemented by the GSI or local authorities (LA). In the 1990s, the EPA took responsibility for groundwater monitoring in Ireland and set up a national monitoring network for groundwater quality and levels. In recent years, and particularly in response to the implementation of the WFD, the groundwater monitoring network in Ireland has been updated and expanded considerably. Cross-correlation between groundwater nitrate data and potentially denitrifying bedrock, taking into account pressures (e.g. nitrogen inputs) and pathway factors, will be appraised and used to evaluate and constrain the Potentially Denitrifying Bedrock map.

## Results
The current Potentially Denitrifying Bedrock map [3] includes bedrock units which are rich in organic carbon or metal sulphides (e.g. pyrite) and will hence potentially reduce nitrate levels through microbially-assisted oxidation of the electron donor substances. The potential for denitrification is qualified through a scoring schema within the map, ranking bedrock units from "definitely containing compounds with the potential to denitrify" (1a) to "almost certainly not containing compounds that have the potential to denitrify" (2b).

The Dinantian Lucan and Ballysteen shaly limestone Formations; the Namurian Clare Shale Formation and the Silurian Tramore Shale Formation were identified as the formations with the greatest potential for denitrification. Devonian Old Red Sandstone, Dinantian Pure Limestones, Dinantian Sandstones and the Dinantian Cork Group (mudstones and sandstones) were identified as having least potential for denitrification.

The new version of the map, currently under development, will benefit from updated GSI bedrock and aggregate potential mapping, as well as recent research results. In addition, the bedrock units identified as potentially denitrifying are being appraised with respect to groundwater nitrate data from the GSI, EPA and Local Authorities. Groundwater nitrate data from monitoring points within different denitrifying settings will be investigated with respect to pressure layers (including land cover, fertiliser application rates, livestock and septic tank density) and pathway layers (including soils, unconsolidated deposits, bedrock geology, aquifer type and climate data). The cross-correlation between nitrate data and bedrock data (taking pressures and pathways into account) will be appraised and used to constrain and evaluate the potentially denitrifying bedrock map.

## Conclusions

This further development of the Geological Survey of Ireland's Potentially Denitrifying Bedrock map will strengthen its role in assessing the groundwater element of the nitrogen cycle in Ireland. The map will provide information for good decision making regarding catchment management and WFD objectives.

## References

[1] Neill, M. 2005. A method to determine which nutrient is limiting for plant growth in estuarine waters— at any salinity. Marine Pollution Bulletin 50, 945–955

[2] Jahangir, M.M.R. et al. 2012a. Groundwater: A pathway for terrestrial C and N losses and indirect greenhouse gas emissions. Agriculture, Ecosystems and Environment 159, 40–48.

[3] Geological Survey of Ireland, 2011a. Bedrock units with the potential for denitrification. Unpublished report and map.

[4] Environmental Protection Agency. 2013. A Risk-Based Methodology to Assist in the Regulation of Domestic Waste Water Treatment Systems. Available from www.epa.ie

[5] Jahangir, M.M.R. et al. 2012b. Denitrification potential in subsoils: a mechanism to reduce nitrate leaching to groundwater. Agriculture, Ecosystems and Environment 147, 13–23.

[6] Geological Survey of Ireland, 2011b. 1:100,000 Draft Aggregate Potential map. Available from www.gsi.ie

[7] Orr, A. 2014. Hydrogeological influences on the fate and transport of nitrate in groundwater. Doctor of Philosophy thesis, School of Planning, Architecture and Civil Engineering, Queens University Belfast.

[8] McAleer, E., Mellander, P.E., Coxon, C.E., Richards, K.G. and Jahangir, M.M.R. 2015. Groundwater denitrification in two agricultural river catchments: influence of hydro-geological setting and aquifer geochemistry. Proceedings of the EGU General Assembly. Available from http://adsabs.harvard.edu/abs/2015EGUGA..1712889M
MYCORRHIZAL INOCULUM EFFECTS ON NITROGEN UPTAKE AND LEACHING
IN ENERGY CROP SPECIES FERTILIZED WITH DIGESTATE LIQUID FRACTION IN
MESOCOSM CONDITION

Caterina Caruso¹, Carmelo Maucieri¹, Alberto Barco¹, Antonio C. Barbera², Maurizio Borin¹

¹Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE) - University of Padua, Legnaro (PD), Italy, ²Department of Agriculture, Food and Environment (Di3A) - University of Catania, Catania (CT), Italy

Objectives

Large amounts of chemical fertilizers are generally applied in conventional agriculture, with potential nu-
trient losses, such as nitrogen (N) and phosphorus (P), which are among the top environmental threats of
pollution to ecosystems worldwide. Organic fertilizer such as digestate, byproduct of biomasses anaerobic
digestion, is an alternative to mineral ones. Arbuscular mycorrhizal fungi (AMF) are a very widespread
communities of soil fungi, which play an important role in the nutrient cycling processes. It has been shown
that AMF could reduce N and P leaching losses and increase plants nutrient uptake, they can promote sus-
tainable nutrient cycling but the effects on N cycling are context dependent [1]. The aim of the trial was to
evaluate the effect of AMF inoculum on N uptake and leaching in six annual and perennial herbaceous crops
fertilized with digestate liquid fraction (DLF) in mesocosm condition.

Method

The trial conducted at the Experimental Farm “L. Toniolo” (45°20’ N; 11°57’ E), began in 2014 and it is still ongoing. The experimental design is a split-plot with AMF inoculation as the main-plot, and plant species as the sub-plots replicated four times, which consists of 6 species (Giant reed, Miscanthus, Jerusalem artichokes, Lolium, Corn and Sorghum) for a total 48 concrete growth boxes (2x2 m side). The growth boxes were installed with the top surface at 1.3 m above ground level, to avoid water table influence, the bottom open to allow water percolation and were filled with fulvi-calcaric Cambisol. Before the experiment started, ceramic suction plates were installed in 18 growth plots at a depth of 0.90 m and connected to a suction system to sample percolation water.

DLF, obtained from anaerobic digestion of cattle slurry and manure, maize silage and flour, was distributed on soil surface (April 1st 2014 and March 19th 2015) at dose of 250 kg N ha⁻¹ box⁻¹. AMF (Glomus spp.) inoculations were carried out during transplanting or sowing at dose of 500 propagules m⁻². The perennial species were transplanted on February 2014, lolium was sowed on April 2014 while sorghum and corn on April 2014 and 2015. Plants were harvested cutting all boxes total aboveground biomass as follows: one or two cuts for Jerusalem artichokes, three cuts for sorghum, two cuts for lolium and one cut for giant reed, miscanthus and corn. Biomass dry weight was obtained in a thermo-ventilated oven at 65 °C, until the constant weight was reached. A CNS Macrovario combustion analyzer (Elementar Analysensysteme GmbH, Germany) was used to determine the biomass N content. During the trial percolation water samples were taken, at 3 different times, in the 60 days after DLF spreading in 2014 and in the 45 days after DLF spreading in 2015 (spring period); and 5 times after the first growing season from December 2014 to 2015 DLF spreading (winter period). 181 percolation water samples were collected and analyzed to detect TKN, NO₃⁻-N and NH₄⁻-N concentrations in spring samples and TKN and NO₃⁻-N concentrations in winter ones.

Results

AMF inoculation significantly (ANOVA p<0.05) increase (+23.7%) giant reed (22.8±1.5 Mg ha⁻¹) and de-
crease (-16.7%) sorghum (36.6±4.3 Mg ha⁻¹) dry biomass production. No significant effect AMF inoculation
exert for the other species with an average yield of 32.0±1.7, 28.9±5.9, 19.0±2.0 and 7.9±0.9 Mg ha⁻¹ for
corn, Jerusalem artichoke, miscanthus and lolium, respectively. AMF inoculation did not show any signifi-
cant effect on N-uptake (32.6±12.5 and 30.8±14.0 g N m⁻² with and without inoculation, respectively). On
the average of AMF inoculation and cuts, the N-uptake for sorghum (42.3±8.1 g m⁻²), Jerusalmen artichokes
(41.6±20.4 g m⁻²) and corn (38.0±2.0 g m⁻²) was not significantly different among them, but significantly (ANOVA p<0.05) higher than giant reed (26.6±7.1 g m⁻²), lolium (22.0±3.4 g m⁻²) and miscanthus (19.1±2.6 g m⁻²). The high standard deviation in Jerusalem artichoke is due to the different N-uptake between the plots managed with one (23.3±6.6 g m⁻²) or two cuts (59.9±6.1 g m⁻²). Except for lolium, miscanthus and Jerusalem artichoke, managed with one cut, the other crops have N uptake higher than that supplied with DLF (25 g m⁻²). In 2015 spring TKN and NH₄-N concentration in percolation water were significantly (Mann-Whitney test p<0.05) lower (0.7 times) and higher (1.7 times), respectively, than 2014. AMF inoculation didn't show effect on N content in the percolation water during 2014-spring season, probably due to the short time after experiment beginning. Instead, in 2015, AMF inoculation showed a significant (Mann-Whitney test p<0.01) lower NH₄-N (-52.2%) and higher NO₃-N (+73.8%) concentrations, than in the un-inoculated plots, which presented median values of 2.42 and 17.30 mg L⁻¹ for NH₄-N and NO₃-N, respectively. In spring 2014, we detected in the percolation water the lowest (0.71 mg L⁻¹) and the highest (2.26 mg L⁻¹) NH₄-N content for giant reed and lolium, respectively. Opposite trend was observed for NO₃-N with 33.31 mg L⁻¹ for giant reed and 14.58 mg L⁻¹ for lolium. During winter season, the lowest NO₃-N concentration in the percolation water was found with lolium (1.40 mg L⁻¹), whereas the highest one with corn (27.72 mg L⁻¹). AMF inoculation significantly (Mann-Whitney test p<0.001) increases (2 times) the NO₃-N percolation compared un-inoculated boxes (14.05 mg L⁻¹). Evaluating the effect of cuts number on N percolation for Jerusalem artichoke, no effect was observed during winter season for both TKN and NO₃-N. Whereas in spring 2015 the percolation water from the boxes managed with two cuts showed a significant (Mann-Whitney test p<0.05) lower concentration for TKN (-38.8%) and NH₄-N (-51.6%), than in boxes managed with one cut (median concentration of 4.29 and 2.54 mg L⁻¹ for TKN and NH₄-N, respectively). No effect was observed considering NO₃-N with a median concentration of 24.40 mg L⁻¹.

## Conclusions

AMF inoculation increase giant reed and decrease sorghum dry biomass production, whereas no effect exerts on the others species. AMF inoculation had no clear effect on plants N-uptake, whereas after the first growing season significantly increase the NO₃-N concentration in percolation water. After the first DLF application AMF inoculation did not influence the N content in the percolation water although, after the second digestate distribution, it decrease NH₄-N and increase NO₃-N. The latter result seems confirm that AMF symbiosis favorites N uptake as NH₄ rather than NO₃ as previously reported by [1], [2] and [3]. The two cuts management of Jerusalem artichoke determine lower TKN and NH₄-N leaching, whereas no effect exerted the management on NO₃-N percolation. The results are undoubtedly interesting, but they have to be considered with caution since that they were obtained only during the first cropping season therefore further results are needed to confirm our findings.

## Acknowledgment

Research was supported by ValDige project "Valorizzazione del digestato per la riduzione delle perdite di CO₂" DGR n°1604 del 31/07/2012 financed by PSR Regione Veneto (2007-2014) misura 124, Domanda n. 2307827.

## References

[1] Bender, F.S., Conen, F., Van der Heijden, M.G.A. 2015. Soil Biology & Biochemistry 80, 283-292

[2] Govindarajulu, M., Pfeffer, P.E., Jin, H., Abubaker, J., Douds, D.D., Allen, J.W., Bücking, H., Lammers, P.J., Shachar-Hill, P. 2005. Nature 435, 819-823.

[3] Tanaka, Y., Yano, K. 2005. Plant, Cell & Environment 28, 1247-1254.
# SIMULATIONS OF NITROGEN DYNAMICS AND LOSSES IN AGRICULTURAL SOILS IN LOMBARDY REGION UNDER DIFFERENT CROPPING SYSTEMS

Silvia Renata Motta, Andrea Giussani, Carlo Riparbelli, Stefano Brenna

ERSAF, Lombardy Regional Agency for Agriculture and Forestry, Milan, Italy

## Objectives

In order to assess the impact of the Italian requested derogation (Nitrate directive) on water quality, nitrogen losses to groundwater from the main agricultural systems in the specific conditions of the Lombardy region have been estimated through the ARMOSA simulation model.

## Method

ARMOSA [1] is a model developed to define a methodology for the assessment of soil quality and nitrate vulnerability in arable systems in Lombardy plain; it was calibrated and validated through a large set of data observed in six monitoring sites [2]. The aim of the model is to simulate water and nitrogen dynamics in the soils representative of the Po valley agricultural areas, under different climatic conditions, crops and management practices, in order to have an instrument to extend the results of field trials to larger areas and to perform scenarios analysis.

Simulations have been provided using the model ARMOSA to compare the environmental performance of 3 different maize-based agricultural systems:

1. Silage maize (late maturing maize, class FAO 700);

2. Silage maize (class FAO 600) + Italian ryegrass;

3. Silage maize (late maturing maize, class FAO 700) + wheat + sorghum + winter cover crop

The aim of these simulations was to compare the nitrogen outputs (N uptake, leaching and volatilisation) under different manure management and to evaluate the impact on the environment. These 3 scenarios were considered:

- scenario 1: application of 170 kg N ha-1 year-1 from manure;

- scenario 2: application of 250 kg N ha-1 year-1 from manure;

- scenario 3: application of 300 kg N ha-1 year-1 from manure.

Scenarios rely on the assumptions that despite an increase in the level of nitrogen from livestock manure, the total amount of nitrogen applied to the field does not vary (365 kg N ha-1 year-1) increasing the theoretical nitrogen efficiency (0.5, 0.6, 0.7) of manure.

These cropping systems have been simulated and compared considering four different soils, characteristic of Lombardy and Piedmont regions:

Soil 1: Luvisol (WRB, 2006), (87) representative of the central and high plain, with a coarse loamy texture;

Soil 2: Luvisol (WRB, 2006-462) representative of older surfaces with a coarse silty texture;

Soil 3: Cambisol (WRB, 2006-112) representative of the medium plain with a loamy texture;

Soil 4: Vertic Cambisol (WRB, 2006-144) representative of the low plain of Lombardy with a silty clay loamy texture.
## Results

The simulation results show that despite an increase of nitrogen from livestock manure distributed to crops, the nitrogen losses (average values) through leaching or volatilisation processes notably decrease between the scenario 1 (application of 170 kg N ha-1 year-1 from manure, NVZ) and the scenarios 2 (application of 250 kg N ha-1 year-1) and 3 (application of 300 kg N ha-1 year-1).

The percentage distribution of nitrate concentration (mg l-1) in drainage water resulted to be affected by the level of fertilisation with organic N: globally, cases with a nitrates concentration higher than 50 mg l-1 are about 50% in scenario 1 (application of 170 kg N ha-1 year-1 from manure) and decrease to 30% in scenario 3 (application of 300 kg N ha-1 year-1).

The ANOVA pointed out the high significance of correlation between the crop rotation and the N losses, with a better environmental performance where soils are covered all year round by crops.

The effect of the crop rotation is confirmed also through the shape of the curves obtained by the correlation between the N leaching (kg ha-1 year-1) and the water inputs (rain + irrigation mm): the slope of the curve strongly decreases from the “maize” rotation to the “maize-wheat-sorghum-cover crop” rotation (confirming a lower trend to leach), with an additional small reduction going from scenario 1 (application of 170 kg N ha-1 year-1 from manure) to scenario 3 (application of 300 kg N ha-1 year-1).

The balance between nitrogen inputs and outputs was also evaluated for the different crop rotations and scenarios to allow the analysis of the increasing or decreasing of the soil N content in organic matter over the years of simulation. Nitrogen sequestration rates were estimated by calculating the mean difference between the final and initial organic N, using soil data to a depth of 40 cm from the latest year of simulations.

Simulation results suggest that scenarios where the soil is fertilised with high amount of organic N (250-300 kg N ha-1 year-1) are more stable with respect to soil organic carbon levels, while low input of manure (170 kg N ha-1 year-1) could lead to a loss of carbon and nitrogen (about 10-15 kg N ha-1) from the soils, in particular where maize is a monoculture or the prevalent crop, as it is in the intensive cropping systems of the Lombardy and Piedmont plain. On the other side, the apparent accumulation of nitrogen (30-50 kg N ha-1) under the other rotations seems to be consistent with the initial simulated low organic matter content (<2%) of soils.

## Conclusions

The ARMOSA simulation results highlighted that scenario 3 with high organic N can be considered as an interesting solution to Lombardy soil. In fact, the greater amount of manure does not improve nitrogen losses, the leaching decrease from 55.99 (scenario 1) to 41.04 kg N ha-1 year-1 (scenario 3).

Silage maize in a double-cropping system with Italian ryegrass or silage maize in rotation with wheat, sorghum and cover crop had an high N uptake and it decrease of the N losses in winter season.

Finally, management adopted under scenario 3 can help improving the efficiency of manure use and reducing the use of mineral fertilizer by the farmer.

## Reference

[1] Acutis M., Ducco G., Grignani C., 2000. Stochastic use of the LEACHN model to forecast nitrate leaching in different maize cropping systems. European Journal of Agronomy, 13: 191-206

[2] Perego A., Giussani A., Sanna M., Fumagalli M., Carozzi M., Alfieri L., Brenna S., Acutis M., 2013. The ARMOSA simulation crop model: overall features, calibration and validation results. Italian Journal of Agrometeorology 3:23-38.
# EFFECT OF INTEGRATED FERTILIZATION AND COVER CROPPING ON N₂O LOSSES IN AN IRRIGATED MEDITERRANEAN MAIZE FIELD

Guillermo Guardia¹, Diego Abalos¹, Sonia García-Marco¹, Laura M. Cárdenas², Elizabeth R. Dixon², Antonio Vallejo¹

¹ETSI Agronomos, Technical University of Madrid, Madrid, Spain, ²Rothamsted Research, North Wyke, Devon, UK

## Objectives

Agronomical and environmental benefits are associated with replacing winter fallow by cover crops (CC). Yet, the effect of this practice on nitrous oxide (N₂O) emissions remains poorly understood. The objective of this study was to evaluate the effect of two different CC species (barley and vetch) and fallow on N₂O emissions during the CC period and during the following maize cash crop period in an Integrated Soil Fertility management (ISFM) system. We also aimed to study the contribution of synthetic fertilizer and other N sources to N₂O emissions through a parallel ¹⁵N labelled fertilizer experiment.

## Method

The study was conducted at “La Chimenea” field station, located in the central Tajo river basin near Aranjuez (Madrid, Spain), where an experiment involving cover cropping systems and conservation tillage has been carried out since 2006. Soil at the field was a Typic Calcixerept with a silty clay loam texture and basic pH (8.2). The area has a Mediterranean semiarid climate, with a mean annual air temperature of 14 °C. Twelve plots (12m × 12m) were randomly distributed in four replications of three cover cropping treatments (seeded in October 2013), including a cereal and a legume: 1) barley (B) (*Hordeum vulgare* L., cv. Vanesa), 2) vetch (V) (*Vicia sativa* L., cv. Vereda), and 3) traditional winter fallow (F). The cover cropping phase finished on March 2014, with an application of glyphosate, and all the CC residues were left on top of the soil. Thereafter, a new set of N fertilizer treatments was set up for the maize cash crop phase. The fertilizer treatments consisted of ammonium nitrate (AN) applied on 2nd June at three rates: 170, 140 and 190 kg N ha⁻¹ in F, V and B plots, respectively, according to ISFM practices. For the calculation of each N rate, the N available in the soil, the expected N uptake by maize crop, and the estimated N mineralized from V and B residues were taken into account. In order to determine the amount of N₂O derived from the N fertilizers, double-labelled AN (¹⁵NH₄¹⁵NO₃, 5 % atom ¹⁵N) was applied on 2m x 2m subplots established within each plot at a rate of 130 kg N ha⁻¹. Nitrous oxide was sampled using opaque manual circular static chambers and measured by gas chromatography. Stable ¹⁵N isotope analysis of N₂O contained in the gas samples was carried out on a trace gas analyzer (using cryo-trapping and cryo-focusing) coupled to a 20/22 isotope ratio mass spectrometer at Rothamsted Research North Wyke. Soil mineral N concentrations, soil temperature and moisture, dissolved organic carbon and GHG fluxes were also measured during the experiment.

## Results

The ISFM resulted in low cumulative N₂O emissions (0.57 to 0.75 kg N₂O-N ha⁻¹) and N surplus (31 to 56 kg N ha⁻¹) for all treatments. The presence of CCs increased N₂O emissions during the intercrop period compared to F (1.6 and 2.6 times in B and V, respectively), but the intercrop period had a low impact in annual N₂O losses (8, 10 and 21% of total cumulative emissions in F, B and V, respectively). Average topsoil nitrate (NO₃⁻) was significantly higher in V, which was the treatment that led to the highest N₂O emissions during this phase. Legumes such as V are capable of biologically fixing atmospheric N₂, thereby increasing soil NO₃⁻ content with potential to be denitrified.

The ISFM resulted in similar cumulative emissions for the CCs and F at the end of the maize cropping period. Barley-residue plots had higher N₂O emissions than fallow or V-residue plots (at the 10% significance level). The higher C:N ratio of the B residue led to higher DOC contents in these plots and a greater proportion of N₂O losses from the synthetic fertilizer in these plots, when compared to V. Taking into account the whole intercrop-maize cycle, the N₂O Emission Factor ranged from 0.2 to 0.6% of synthetic N applied,
which were lower than IPCC default value of 1%.

The replacement of bare fallow by CCs, in combination with an ISFM, did not increase soil N₂O emissions in the overall CC-cash-crop cycle. This fact should be taken into account since the potential of CCs to reduce indirect losses (through the abatement of NO₃⁻ leaching) and to increase C sequestration has been demonstrated in previous studies.

## Conclusions

Our study confirmed that the presence of CCs (particularly V) during the intercrop period increased N₂O losses. Conversely, by employing ISFM, similar N₂O emissions were measured from CCs and F treatments at the end of the whole cropping period, with low N surpluses. Our results highlight the critical importance of the cash crop period on total N₂O emissions, and demonstrate that the use of either legume or non-legume CC combined with ISFM offers an opportunity for N₂O mitigation.
# STATISTICAL MATCHING TO OBTAIN BETTER ESTIMATES AT REGIONAL SCALE

Co Daatselaar, Ton Van Leeuwen, Marga Hoogeveen

*Agricultural Economics Research Institute, The Hague, The Netherlands*

## Objectives

Within the research of the Dutch Minerals Policy Monitoring Program (LMM) insight is desirable for combinations of farm types and (sub-)regions into long term developments of the use and surpluses of nitrogen and phosphate. This information is also useful for regional policies and the EU-Water Framework Directive. LMM can be seen as a subsample of the Dutch Farm Accountancy Data Network (FADN). To improve the reliability of the estimates not only firm data of LMM-farms are needed but also of all farms in the FADN being part of the LMM sample population.

A stratified, disproportional random sample is used for the firm choice for the FADN [1] and LMM to achieve smaller standard errors in the estimates. This type of sampling needs weighing for reliable judgments concerning specific farm types or regions. To improve the weighing a technique for inclusion of additional information is applied.

## Method

Data on use of nitrogen and phosphate and the surpluses on the soil balance were derived from FADN and LMM. The Agricultural Economics Research Institute (LEI Wageningen UR) continuously collects economic, technical and environmental data at farm level in the FADN. For this research data from the period 1991-2013 were used. The datasets of surveys such as FADN and LMM are mainly used to generate statistics for the whole population. Based on the observations and a set of weights an estimate can be made for the population. When making estimations for smaller areas or specific groups the number of sample elements belonging to a region or group can be limited. This results in estimates with a low reliability.

To increase the reliability of estimates additional information can be used for example from the agricultural census. The agricultural census gives a complete list of the population of farms but the amount of information in this census is limited. By an imputation procedure (statistical matching via nearest neighbour) for each farm in the population a set of farms in the FADN sample is selected which resembles the farm as closely as possible [2]. Variables, which are used to decide whether a farm resembles a sample farm (called imputation variables), have been determined before with multiple regression analysis. The imputation variables should be known for all farms in the sample and the population. Based on these variables the distances between all possible combinations are calculated. The sample farm with the smallest distance is regarded as the farm that resembles the population farm as closely as possible. For each farm in the population, 3 most similar farms are selected from the sample to avoid underestimation. These best fits are recorded together with the distance measures.

Based on these best fits, estimates can be made for a set of goal variables, which are known in the sample, but unknown for all population farms. To judge the results of statistical matching compared to not weighing and the standard weighing in FADN the representativeness and the validity of the results are considered.

## Results

Within LMM four soil regions are distinguished: sand, clay, peat and loess. Besides four farm types are considered: arable, dairy, pigs/poultry and other which results in sixteen possible combinations of region and farm type. Because of very limited numbers in the agricultural census pigs/poultry is only considered for the sandy region and in the peat region only dairy is taken into account.

Regression analysis provided for dairy farms the imputation variables distance (in km), farm size (in Dutch Size Units (DSU)), DSU per ha utilized area, percentage livestock units (LSU) pigs/poultry of total livestock units, percentage grassland in utilized area and LSU young stock per dairy cow. For most soil regions DSU/
ha was the most important imputation variable. In the case of arable farms the imputation variables were distance (in km) and the shares of different crops in the utilized area. Distance (in km) and LSU/ha utilized area resulted as imputation variables for pig/poultry farms in the sandy region whereas distance (in km), farm size, LSU/ha and share of grassland turned out to be the imputation variables for farms of other type.

For eleven combinations of farm type and soil region the imputation was run. Nitrogen soil surpluses on arable farms decreased from about 150 kg N per ha in 1991 to about 100 kg N per ha in 2013. For dairy farms the decrease was about 130 kg N per ha: from just above 300 to just below 200. Pig/poultry farms realized smaller decreases, about 20 kg N per ha from 170 to 150. Other farms realized decreases comparable to those of arable farms: from about 240 kg N per ha in 1991 to about 190 kg N per ha in 2013. Main source of the decreases was less use of artificial/chemical fertilizer.

Both on representativeness and validity the use of statistical matching performed better than when using the standard weighing in FADN and much better compared to not weighing. Relative difference compared to relative standard error [1] and comparison of sample results with population averages (for the imputation variables) showed good outcomes for statistical matching. The sensitivity (fluctuation in weighing factors) was only slightly higher for statistical matching due to the fact that statistical matching uses more imputation variables than are used for the stratification in the FADN sample. In the FADN sample only farm type and farm size are used. A leave one out test (the values of a sample farm are estimated by imputing values from one or more other sample farms that are very similar) showed no significant differences between the estimated and the real values for statistical matching.

## Conclusions

In the period 1991-2013 farms in the Netherlands considerably reduced their nitrogen soil surpluses. Main contributor to this reduction was less use of artificial/chemical fertilizer. Comparison of different methods to calculate these nitrogen soil surpluses for specific farm types or regions showed that statistical matching produced the most representative and valid results. The slightly higher sensitivity in the case of statistical matching is a point of attention: it can be reduced for instance by setting a maximum on the weighing factor a sample farm can get.

## References

[1] Veen, H.B. van der, Ge, L., Meer, R.W. van der, Vrolijk, H.C.J. 2014. Sample of Dutch FADN 2012, LEI Wageningen UR, The Hague, report 2014-027

[2] Vrolijk, H.C.J., Dol, W., Kuhlman, T. 2005. Integration of small area estimation and mapping techniques - Tool for Regional Studies. LEI, The Hague, Report 8.05.01
# PROVISION OF DICYANDIAMIDE IN SUPPLEMENTARY FEED AS A TARGETED NITROGEN MITIGATION STRATEGY FOR GRAZING CATTLE: PROOF-OF EFFICACY

Brendon Welten, Stewart Ledgard

AgResearch Ruakura Research Centre, Hamilton, New Zealand

## Objectives

Urine deposition by cattle results in localised patches of high soil nitrogen (N) levels that are the major contributor to N losses from grazed pastures. Dicyandiamide (DCD) is a chemical compound that has shown to be an effective mitigation technology to reduce urinary-N losses from soil. A method to specifically target individual urine patches is by administering DCD directly to grazing ruminants for excretion in the urine. One practical delivery method could be to administer DCD with supplementary feed to grazing cattle.

This paper reports on a series of studies that examined the effect of administering DCD to cattle via grass silage (as a supplementary feed source) on (1) excretion of DCD in urine, (2) efficacy to inhibit nitrification in soil, (3) deposition of DCD in urine patches under grazing and, (4) persistence of DCD in grass silage during storage.

## Method

1. Animal feeding study: Five non-lactating dairy cattle were housed in individual stalls with standard harnesses attached for separate collection of urine and faeces over a 10 day measurement period. The five cows were allocated 2 kg dry matter (DM) of ryegrass silage each morning followed by 8 kg DM of fresh cut pasture with actual intakes recorded daily (total of 10 kg DM offered cow⁻¹ day⁻¹). The grass silage was amended with granular DCD (30 g DCD cow⁻¹ day⁻¹) and a small amount of molasses was used to ensure the DCD adhered to the silage. The cows had free access to water during the entire study with urine and faeces collected from individual cows daily and the DCD concentration determined. Associated measurements included: water intake, N excretion in urine and faeces, animal live-weight and animal welfare.

2. Laboratory soil incubation study: Urine collected from DCD-treated cattle in the feeding study was compared with urine from non-treated cattle spiked with varying rates of DCD (ranging from the equivalent of 0-100 kg DCD ha⁻¹) and a control. These treatments were added to a volcanic ash derived soil (*Typic vitran-dept*) and incubated at 20°C for 104 days. Soil samples were extracted at regular intervals and analysed for ammonium-N, nitrate-N and DCD concentration.

3. Grazing study: Seventeen non-lactating dairy cattle consecutively grazed fenced pasture plots (each 714 m²) over a seven day period. The cattle were also supplemented with grass silage (4 kg DM cow⁻¹ day⁻¹) and had free access to water. An aqueous DCD solution was applied to the silage to potentially achieve a targeted daily DCD intake of 50 g DCD cow⁻¹ day⁻¹. Individual urine patches were soil-sampled over a 6-hour period (0900-1500 h) on four occasions to determine the rate of DCD deposited in urine patches.

4. Baled silage storage study: Aqueous DCD solution was applied to rowed silage immediately prior to being ensiled in plastic (4 replicates). There were also two control (nil-DCD) silage bales. The silage bales were sampled at regular intervals over a 286-day storage period and analysed for DCD concentration and pasture quality parameters.

## Results

The animal feeding study showed that the concentration of DCD in urine from cattle fed DCD-treated pasture silage (30 g DCD cow⁻¹ day⁻¹) markedly increased within the first two days and thereafter remained relatively constant at about 900 mg DCD L⁻¹. The daily recovery of DCD in urine averaged 82% of that administered with 10% in faeces across cattle and measurement days (excluding the first two days). Sampling of individual urinations over a 24 h period showed a diurnal pattern in the concentration of DCD in urine, which peaked at about 9 h after commencing DCD administration. The associated laboratory soil incubation
study showed that the DCD voided in urine prolonged the retention of urinary-N in the ammonium-N form in soil at a similar temporal inhibitory pattern to DCD applied directly to soil at a rate of 50 kg DCD ha⁻¹.
This finding infers no effect of animal feeding on DCD efficacy in soil.

Analyses of soil samples from the 172 urine patches collected in the grazing study revealed that the rate of DCD deposited in urine patches was variable, which showed a positively skewed distribution. The application rate of DCD in urine patches was typically in the range of 20-60 kg DCD ha⁻¹.

The concentration of DCD in stored silage bales decreased over time to approximately 30% of that initially applied after 286 days. The degradation of DCD in grass silage bales was primarily attributed to the high temperatures and low pH associated with ensiled silage that would have denatured the compound.

## Conclusions

These studies have demonstrated that provision of DCD in a supplementary feed source (grass silage) to non-lactating cattle resulted in a large amount (averaged 82% of that administered) being voided in the urine that effectively inhibited nitrification of urinary-N in soil. Under grazing, the rate of DCD deposited in urine patches was variable with the majority of urine patches having an equivalent field application rate in the range of 20-60 kg DCD ha⁻¹. Administration of DCD to grass silage should be undertaken prior to feeding since degradation of DCD occurs when grass silage is stored for a long period (e.g. 280 days). This research highlights the viability of delivering DCD to cattle via supplementary feed as a targeted mitigation strategy to potentially reduce urinary-N losses from grazed pastures.
# DETERMINING THE ROLE OF FUNGI AND BACTERIA IN CO-DENITRIFICATION

David Rex¹, Timothy Clough¹, Gary Lanigan², Karl Richards², Cecile de Klein³, Sergio Morales⁴, Lars Bakken⁵, Md Sainur Samad⁴

¹Lincoln University, Christchurch, New Zealand, ²Teagasc, Johnstown Castle Research Centre, Wexford, Ireland, ³AgResearch, Invermay, New Zealand, ⁴University of Otago, Dunedin, New Zealand, ⁵Norwegian University of Life Sciences, Ås, Norway

## Objectives

Emissions of N₂O, a greenhouse gas, and N₂ may derive from classical denitrification, nitrifer-denitrification, and co-denitrification [1]. Co-denitrification may be significant and has been reported to be responsible for more than 90% of nitrogen gas emissions in grazed grassland [2]. A more detailed knowledge on the fate of applied nitrogen is required to improve nitrogen use efficiency and to provide an understanding for N₂O mitigation options.

The objective of this experiment was to reveal the contribution of fungi and/or bacteria to N₂O and N₂ fluxes following bovine urine deposition to a pasture soil.

## Method

A sandy loam pasture soil was collected (43°38′33.73″S, 172°27′40.38″E) and sieved (2mm). Moistened soil was then placed in jars, 240 single jars (250ml) at a 50% water holding capacity. Jars were divided into six treatments x 5 replicates x 8 sampling times (30 jars each sampling time. Six treatments consisted of a control, urea, urea + streptomycin + penicillin, urea + cycloheximide, urea + captan, urea + streptomycin + penicillin + cycloheximide). Urea was enriched with 15N at 50 atm% and applied at a rate of 1000 kg N/ha to simulate bovine urine deposition. During the experiment the jars were stored in an incubator at 23°C and 55% relative air humidity. At each sampling time (day 1, 7, 13, 19, 25, 31, 40, 49) a set of jars was 'inhibited' as determined by treatment. During the experiment daily gas samples were taken to determine the N₂O-flux rates of all jars and the 15N enrichment of N₂O and N₂. Measurements of surface pH and CO₂-fluxes were also made. Subsamples of the inhibited soils and controls were taken to measure the amount of NH₄⁺, NO₃⁻, NO₂⁻, the dissolved organic carbon and the total carbon/nitrogen ratio in the soil.

## Results

Soil chemistry, fluxes of N₂O and N₂, as affected by treatment, will be presented over time along with their 15N enrichments and their relative contributions to the total flux.

The role and implications of co-denitrification will be further explored with respect to the microbial contributions to the total N₂O and N₂ emissions.

## Conclusions

Preliminary data analysis indicates, differing contributions of fungi and bacteria to the production of gaseous nitrogen compounds.

## References

[1] Spott, O., Russow, R., Stange, C. F. 2011. Soil Biology & Biochemistry 43, 1995-2011

[2] Selbie, D. R., Lanigan, G. J., Laughlin, R. J., Di, H. J., Moir, J. L., Cameron, K. C., Clough, T. J., Watson, C. J., Grant, J., Somers, C., Richards, K. G. 2015. Scientific Reports 5, 17361, PMC4663629
François Visser, Ammar Aziz

University of Queensland, Brisbane, Queensland, Australia

## Objectives

Applied fertiliser is both the biggest input cost and the biggest contributor to GHG's emanating from crop-ping. The N-Smart™ software model provides farmers with a suggested optimal fertiliser application rate based on their yield goal and current fertiliser application regime; as well as the opportunity to simulate different practice change scenarios to explore maximum profit versus lowest environmental impact combinations.

It appears that the current fertiliser recommendation models in Australia may not do justice to the multi-faceted approach that is required to optimise fertiliser management, including recognising that profitability is also a strong sustainability driver for growers.

Farmers need a simple nitrogen management interface whereby they can explore all the different practice change scenarios and outcomes, and it is anticipated that the N-Smart tool meets these requirements. It is the aim of this paper / presentation to highlight the scientific principles that underlies the methodology of the model.

## Method

Industry consultation guided the structure and outcomes of the model:

### Founding Principles:

* An industry / farmer level tool - approximately 15 minutes for N assessment

* Utilises data inputs available at farm level, including soil test reports

* Site and crop specific, incorporating various 'environmental' factors

* Four outputs: Gross profit/ha, carbon footprint/unit, progress (%/unit) and yield/ha

* Graphic output in declining yield curve with optimum fertiliser rate

* Web-based software with customising and scenario planning capability

* Determines progress made in environmental impact improvements (%) through adoption of practice changes

Research shows there are three main factors that have a significant effect on crop nitrogen use efficiency, namely soil mineralised N contributions, crop uptake N / yield conversion ratios and fertiliser application losses (Rochester, I., J. 2011).

Fertiliser derived N normally comprises less than 50 per cent of cotton crop N uptake, therefore we need to maximise N mineralisation in the soil as a 'cheaper' and perhaps less vulnerable N source. Accordingly, a major component of the model is a comprehensive mineralisation module which estimates the amount of nitrogen that will be 'manufactured' during the growing of the crop, given certain environmental parameters.

Research in Australia has shown that optimum uptake N requirement for cotton is approximately 250 kg N per hectare. However, extensive field trials showed that at a common 250 N uptake level, actual yields can vary from 6 bales per hectare to 13 bales, or conversely an N uptake requirement per bale ranging from 13.6 N to 34 N at a common 9 bale yield level. It is therefore important that this conversion efficiency factor is taken into consideration prior to estimating fertiliser N application losses.
None of the commonly applied fertiliser recommendation models in Australia allow for the type of N applied or the method with which it will be applied, and no published information was available. Our research has shown that N application losses can vary between 20% (N26 water run) to 70% (broadcast urea) of total N applied amongst different product / practice combinations. It is therefore important that these distinctions be made in nitrogen modelling.

## Results

For the distinction between fertiliser type and application practice N losses, the following 7 combinations were tested and quantified for N₂O fluxes / losses in field trials:

* Urea broadcast - Dry

* Urea broadcast - Irrigated

* Urea incorporated / banded - Irrigated

* Entec broadcast - Irrigated (denitrification inhibitor)

* Entec incorporated / banded- Irrigated

* N26 - With irrigation

* Anhydrous ammonia liquid - with irrigation

* Control: Nil N, irrigated

The following are the main observations; specific loss factors were determined after further laboratory tests on the effect of soil types, and post facto soil tests and ammonia volatilisation losses at the field trial sites:

* Temperature has marked effect on emission rates

* Limited losses from urea on dry soil surface (including dew), response only came with significant rainfall

* Similar response from urea broadcast irrigated, liquid N 26 with water and anhydrous with water.

* Losses from incorporated urea significantly lower than broadcast urea at first, response only came after second watering event and rain, but then at similar rate of increase.

* Two Entec variations (broadcast and incorporated) were outstanding with near zero emission losses, again with the broadcast variance being higher.

* Control showed surprisingly flat response to the moisture and temperature variations.

Typically fertiliser recommendation models incorporate limited in crop N mineralisation contributions, or exclude it. However, zero N cotton field trials in Australia have shown crop uptake levels of up to 150 units of N per ha. A thorough search of the literature and extensive consultations revealed that there was no industry level broad acre mineralisation simulation model available that could be incorporated into the N-$mart™$ model. The most applicable tool was the Solvita soil CO₂ respiration kits but these parameters had not been adapted for Australian conditions. It was therefore decided to develop a customised forecasting tool based on soluble C and N values linked to validated soil respiration data and resulting mineralisation, based on actual cotton field trials in all the cotton growing regions. Further in crop mineralisation fieldwork will take place during this year's crop. An interim mineralisation methodology has been developed.

It is clear that precision crop N management is a complex and multi-facetted area, with many inter-related factors to consider. To calculate the nitrogen requirement of the crop, the model follows the following 6 sequential steps in order to deal with all the variables is a logical manner:
* 1) Farmer set the target yield: - i.e bales of cotton /ha

* 2) Estimate N/yield conversion: - N uptake / yield efficiency ratio

* 3) Estimate total soil N contribution: - soil mineralisation plus 'starter' N

* 4) Estimate fertiliser application losses (%): - for different products & practices applied

* 5) Calculate fertiliser balance to apply: - (1\*2\*3)/4

## Conclusions

Sustainability is recognised as a process of continuous improvement, however, growers need to be empowered with fit-for-purpose tools whereby they can track their progress and explore financially viable alternatives to guide their decision-making.

The scientific credentials and robustness off the N-Smart™ tool is an ongoing process as the results of further field trials and published data are incorporated into back-end of the model. Further, 'sustainability needs to pay to be sustainable', which required establishing all the economic parameters pertaining to the 15 different cotton growing regions in Australia.

Tools that require farmers to complete a lengthy spreadsheet are doomed to fail, this was successfully addressed by pre-populating the different grower regions with defaults data sets. The model guides the user to customise the parameters for each paddock/crop, taking the environmental and soil conditions into account, within a time frame of 15 minutes.

Growers are encouraged to run different scenarios: tracking the effect of parameter changes on yield and sustainability outputs at different N levels; including the corresponding gross margins. It is particularly important to consider the types of fertilisers and application practices undertaken by growers as these have significant effects on N losses. Likewise uptake N/yield conversion is an important aspect. As indicated above, the difference between a good and a poor conversion efficiency can be 20 units of N per bale which amounts to a relative loss of 200 units of N at a yield of 10 bales per hectare, which could overshadow fertiliser application losses.
# N₂O EMISSIONS OF IRRIGATED MAIZE MANAGED UNDER DIFFERENT SOIL TILLAGE SYSTEMS AND N FERTILIZATION RATES IN A MEDITERRANEAN AGROECOSYSTEM

Evangelina Pareja-Sánchez¹, Daniel Plaza-Bonilla²,³, Jorge Álvaro-Fuentes², Carlos Cantero-Martínez¹

¹Crop and Forest Sciences Department, Unidad Asociada EEAD-CSIC, Agrotecnio. University of Lleida, 25198 Lleida, Spain, ²Departamento de Suelo y Agua. Estación Experimental de Aula Dei (EEAD-CSIC), 50056 Zaragoza, Spain, ³INRA, UMR-AGIR, 31326 Castanet-Tolosan, France

## Objectives

Soil nitrous oxide (N₂O) emissions resulting from agricultural management practices, increase the atmospheric concentrations of N₂O, contributing to global warming. The aims of this work were: i) to quantify the emission of N₂O and maize yields according to different soil management practices and N fertilization rates and ii) to analyze the impact of environmental and soil variables on the emissions in a semiarid area recently transformed to irrigation under Mediterranean conditions.

## Method

The study site was located in Agramunt (NE Spain; mean annual precipitation: 430 mm). A long-term tillage and nitrogen experiment (established in 1996) under dryland barley production was transformed to irrigated maize with solid set sprinklers in 2015. Three types of tillage (no-tillage, NT; reduced tillage, RT and conventional intensive tillage, CT) and three mineral N fertilization rates (0, 200, 400 kg N ha⁻¹) were compared. The NT treatment consisted of weed control with a non-selective herbicide while the CT treatment consisted of one pass of subsoiler to 35 cm depth followed by one pass of a disk plough to 20 cm depth. Finally, the RT treatment consisted of one pass of a strip-till implement on the sowing line to 30 cm depth reducing the surface tilled to a 20 %. The experiment was laid out in a randomized block design with three replications. N fertilization rates were split in one pre-sowing and two top-dressing applications. Soil N₂O fluxes were measured weekly during the growing season (April to November), being more intense during fertilizer applications (i.e. 24 h. prior and 3 h. and 72 h. after) using non-steady state static chambers [1]. Gas samples were taken at 0, 20 and 40 min after the closure of the chamber and stored in vials, being subsequently analyzed by a gas chromatography system equipped with an ECD detector. Gas fluxes were calculated taking into account the linear increase in the N₂O concentration inside the chamber with time (40 min) and correcting the values for the air temperature. On each sampling date and close to each chamber, soil mineral N (as ammonium and nitrate), temperature and volumetric soil water content of the 0-5 cm depth were also quantified. The water-filled pore space (WFPS) was calculated with soil bulk density, which was quantified monthly. Grain yield was harvested with a commercial combine, dried and weighed. Finally, the yield-scaled N₂O emissions, expressed as kg of CO₂ equivalents emitted per kg of grain produced, were calculated taking into account a global warming potential of 265 [2].

## Results

Soil N₂O emissions were significantly affected by tillage, N fertilization, sampling date and their interactions. Mean N₂O fluxes decreased in the order NT > RT > CT, being 0.305, 0.171 and 0.095 mg N₂O-N m⁻² day⁻¹, respectively. Increasing N fertilizer rates led to a significant increase in the emissions, i.e. 0.02, 0.16 and 0.40 mg N₂O-N m⁻²d⁻¹ for the 0, 200, 400 kg N ha⁻¹ treatments, respectively. A significant tillage x nitrogen interaction was found on N₂O fluxes. While the control and the 200 kg N ha⁻¹ treatments led to similar N₂O emissions between tillage systems, the application of 400 kg N ha⁻¹ led to greater values in NT, followed by RT and CT (0.65, 0.33 and 0.19 mg N₂O-N m⁻²d⁻¹, respectively).

The WFPS was affected by tillage and N fertilization treatments. Mean WFPS was 50%, 36% and 31% for the NT, RT and CT treatments, respectively. No-tillage presented greater WFPS than CT in most sampling dates. This result was probably due to: (i) lower soil structural stability under long-term CT compared to NT [3] which could have reduced water infiltration due to soil crusting, as a consequence of organic matter and aggregate stability reduction and (ii) greater water storage under NT compared to CT [4]. The sampling date
affected significantly the dynamics of NO₃⁻ and NH₄⁺ in the soil, which was influenced by N fertilizer applications. Those applications led to punctual increases in soil mineral N, which produced N₂O emission peaks, especially under NT, as a consequence of a greater WFPS. Similar results were observed by Sánchez-Martín et al., 2010 [5].

Grain production was greater in NT and RT than in CT, with 11406, 9548 and 5594 kg ha⁻¹, respectively. The lower amount of water in the soil in CT as a result of a reduced infiltration of irrigation water would have caused a severe hydric stress to maize, reducing its yield. Also, significant differences on grain production were found between N fertilization treatments with greater values when applying 200 kg N ha⁻¹ compared to the control treatment (10394 and 7705 kg ha⁻¹) and intermediate values when applying 400 kg N ha⁻¹ (8448 kg ha⁻¹). The application of 200 kg N ha⁻¹ under NT led to the highest production (12747 kg ha⁻¹) without being significantly different than the rest of treatments.

Only the N fertilization treatments affected significantly the yield-scaled N₂O emissions, with greater values when increasing the N fertilizer rate: 0.001, 0.012 and 0.035 kg CO₂ equiv. kg grain⁻¹ for the 0, 200 and 400 kg N ha⁻¹ treatments, respectively. Contrarily, no differences on the yield-scaled N₂O emissions were found between tillage systems or the interaction between tillage and N fertilization treatments.

## Conclusions

The results of this study show that NT led to higher emissions of N₂O to the atmosphere than RT and CT. N fertilization increased N₂O emissions when a high rate of mineral N was used and, especially, just after the application of N fertilizer. The use of NT increased the production of grain, while the use of CT led to very low yields. However, only the N fertilizer treatments affected significantly the yield-scaled N₂O emissions, which increased at increasing N rates. Our preliminary data shows that tillage and N fertilization have a profound effect on N₂O emissions and maize production in recently transformed to irrigation Mediterranean agroecosystems.

## Acknowledgements

We would like to thank the field and laboratory technicians Javier Bareche, Carlos Cortés and Silvia Martí. This research work is financially supported by the Spanish Ministry of Education and Science (grants AGL2013-49062-C4-1-R).

## References

[1] Hutchinson and Mosier. 1981. Soil Sci. Soc. Am. J. 45, 311-316.

[2] IPCC. 2013. Fifth Assessment Report (AR5) of the IPCC.

[3] Plaza-Bonilla et al. 2013. Geoderma 193-194, 76-82.

[4] Cantero-Martínez et al. 2007. Ann. Appl. Biol. 150, 293-305.

[5] Sánchez-Martín et al. 2010. Eur. J. Soil Sci. 61, 710-720.
# UREASE ACTIVITY AND POTENTIALLY MINERALIZABLE NITROGEN INFLUENCED BY DIFFERENT SOIL MANAGEMENT SYSTEMS

Diana Martin-Lammerding¹, Vladislav Motyzhov², Mª Mar Albarrán¹, José Luis Tenorio¹

¹Nacl. Invest. & Tecnol. Agr. & Alimentaria, Madrid, Madrid, Spain, ²Universidad Complutense Madrid, Madrid, Madrid, Spain

## Objectives

The objectives of this work were: (1) to study the impact of long term tillage systems and crop rotation on some parameters directly related to N availability like urease activity and potentially mineralizable nitrogen (PMN), and (2) to evaluate the correlations among the studied parameters (urease activity, PMN, total soil nitrogen (SN) and soil mineral nitrogen).

## Method

The study was conducted in a field trial located in Alcalá de Henares, Spain (40° 32'N, 3° 20'W; 600 m.a.s.l.). Soil was classified as a Calcic Haploxeralf and the area is characterized by low and irregularly distributed rainfall (353 mm year-1). The experimental design was established on 1994 and consisted in a split plot with four randomized blocks. The main factor was tillage system (Conventional Tillage (CT), Minimum Tillage (MT) and No Tillage (NT)). The secondary factor was the cropping background, either a wheat monoculture or a four-year crop rotation: fallow-wheat-vetch-barley. Soil sampling was conducted in October 2013, one week before seeding. 24 subplots out from the whole 60 were sampled, 12 from the wheat monoculture and 12 from the rotation after barley harvest and before the fallow period. Two separated depths were collected, 0-7.5 and 7.5-15 cm. Total soil nitrogen was determined by the Kjeldahl method. Soil mineral nitrogen was extracted by shaking 5 g soil with 50 mL of a KCl solution (2M) during 30 min. NH4+ and NO3- were measured with the respective cassettes of a FIAstar 5000 Analyzer (FOSS). Potentially mineralizable nitrogen (PMN) was estimated by an anaerobic soil incubation for 7 days [1]. The extraction and measurement of the ammonia was performed as above. PMN was calculated as the difference between NH4 produced during the incubation minus the initial soil NH4 content. Extracellular urease activity was estimated following the non-buffered incubation method [2], [3]. Briefly, 5g of fresh soil were incubated with 2.5 mL urea solution (0.08M) at 37°C. After 2h, ammonia was extracted with the addition of 50 mL of an acidified KCl 1M (HCl 0.01M) solution and shacked during 30 min. Control solutions were prepared as above with 2.5 mL distilled water, the urea being added after the incubation and immediately before the addition of the KCl/HCl solution. The resulting suspensions were filtered and NH4+ was colorimetrically determined with a FIAstar 5000 Analyzer (Foss). Variance analysis was performed with the GLM procedure of SAS and mean separation was tested with the least square means option.

## Results

Soil water content (SWC) at sampling in October 2013 was close to that of field capacity and did not vary neither with depth, tillage nor rotation. Mean value of SWC was 128 g kg-1. Results showed that except for SWC and N-NH4, the studied parameters varied significantly with depth. Those differences occurred mainly under NT and MT plots due to the accumulation of crop residues on the surface, whereas under CT, mould-board ploughing buried crop residues every year resulting in a homogenized soil layer until 20-30 cm depth. Differences in crop residues placement and tillage intensity led to differences in Soil Organic Matter (SOM) content and localization, affecting other soil properties. PMN content in the surface of NT plots accounted to 51.4 mg N-NH4 kg-1 7d-1, whereas in the deeper layer PMN was significantly lower, only 14.7. Mean PMN content under CT plots was 20.4 mg N-NH4 kg-1 7d-1. On the other hand, urease activity in the surface of NT plots was 69.1 mg N-NH4 kg-1 2h-1 whereas in the deeper layer 26.2. Mean urease activity under CT plots reached 37.7 mg N-NH4 kg-1 2h-1.

NT plots showed significantly higher PMN and urease activity than CT plots, mainly in the soil surface. In the first 7.5 cm, PMN was a 55 % higher under NT than under CT, and urease activity a 35 %. A higher N immobilization or reduced mineralization rate under NT plots may explain the higher PMN founded.
ences between subplots under wheat monoculture compared to those subplots from the crop rotation were
significant only in the case of urease activity. Unlike other authors findings [4], we found significant higher
values of urease activity in the surface of the monoculture subplots (61.1 mg N-NH4 kg-1 2h-1) than under
the rotation subplots (49.9). Those differences might be the result of long fallowing every four years under
the subplots from the crop rotation. Including fallow periods in the rotation limited not only C input but also
the rizosphere activity resulting in reduced microorganism activity.

As expected, both PMN and extracellular urease activity significantly correlated with SN (p<0.0001). PMN is the result of the net mineralization of several easily decomposable organic matter pools, whereas urease is related to the terminal N-cycle, in which soil organic nitrogen is transformed into ammonia [5]. PMN and urease activity were also highly correlated (r2=0.92, p<0.0001). We expected PMN or urease activity to correlate with N-NH4 content but neither of them did. In our study N-NH4 represented around a 1.5% of SN, being the majority of SN organic nitrogen. Ammonia expected suppression effect on urease activity was not noticeable under the semiarid conditions of the study.

Conclusions

This study was our first attempt to understand some different steps of the N biogeochemical cycle in semiarid soils. Managing and understanding N availability indices is critical in order to improve soil natural fertility and reducing N fertilization in agro-ecosystems.

Acknowledgments

Financial support was provided by the Regional Government of Madrid and Nacl. Invest. & Tecnol. Agr. & Alimentaria (P2013-ABI-2717-AGRISOST and RTA2013-00009-C02-01). We would like to thank the field assistants of La Canaleja for their work.

References

[1] Drinkwater, L.E., C.A. Cambardella, J.D. Reeder, and C.W. Rice. 1996. Potentially mineralizable nitrogen as an indicator of biologically active soil nitrogen, pp. 217-229, In J. W. Doran, and A. J. Jones, eds. Methods for Assessing Soil Quality, SSSA, Madison, USA.

[2] Kandeler, E., and H. Gerber. 1988. Short-term assay of soil urease activity using colorimetric determination of ammonium. Biol. Fertil. Soils. 6: 68-72.

[3] Kandeler, E. 1993. Kolorimetrische Bestimmung der Urease-Aktivität, pp. 186-189, In F. Schinner, R. Öhlinger, E. Kandeler, R. Margesin, eds. Bodenbiologische Arbeitsmethoden. Springer-Verlag, Berlin, Germany.

[4] Acosta-Martinez, V., J. Moore-Kucera, J. Cotton, T. Gardner, and D. Wester. 2014. Soil enzyme activities during the 2011 Texas record drought/heat wave and implications to biogeochemical cycling and organic matter dynamics. Appl. Soil Ecol. 75: 43-51.

[5] Caravaca, F., G. Masciandaro, and B. Ceccanti. 2002. Land use in relation to soil chemical and biochemical properties in a semiarid Mediterranean environment. Soil Till. Res. 68: 23-30.
# FERTILISER N RECOVERY AND MINERALISATION SUPPLY IN A MEDITERRANEAN MID-TERM COVER CROP-MAIZE ROTATION SYSTEM

Jose L. Gabriel, Maria Alonso-Ayuso, Irene García-González, Chiquinquira Hontoria, Miguel Quemada

Universidad Politécnica de Madrid, Agriculture production Department, Madrid, Spain

## Objectives

The use of cover crops is increasing mainly because of environmental benefits, but also because of economic and agronomic advantages. Cover crops reduced nitrate leaching in many regions and they are an important tool reducing nitrate leaching risk. Moreover, cover crops can increase organic matter, water retention capacity, soil aggregate stability, nutrient supply and soil erosion control. But controversial effects on the yield and N uptake of the following main crop have been reported depending on the cover crop species, the region or the management.

The main goal was to study the effect of replacing fallow with cover crops in a long-term maize production system under limited N fertilisation supply. The specific objectives were to determine the effect on (i) the crop yield and N uptake, and (ii) the recovery of ¹⁵N fertiliser applied to maize.

## Method

The study was conducted during 2 years (08/10/2012 to 25/09/2014) in a silty clay loam in Aranjuez (Spain), Mediterranean semiarid. Plots were included in a mid-term experiment based on three winter cover crop treatments sowed every year since October 2006. The treatments were barley (*Hordeum vulgare* L.), vetch (*Vicia sativa* L.) and fallow, and the design corresponded to four replications randomly distributed in twelve plots (144 m²). Cover crops were sown in early October and killed in late winter (Glyphosate 2% and straw chopped when dry), allowing planting of maize (*Zea mays* L.) on the entire trial in early April, and harvested by the end of September. One microplot (2 m x 2 m) was established within each plot to monitor ¹⁵N-labeled fertiliser uptake, recovery and fate. Each microplot received 130 kg N ha⁻¹ as ammonium nitrate enriched (5.0 % excess ¹⁵N), when corn had 4-6 leaves. The rest of the experimental area received the same N application but with no-labelled fertilizer. Irrigation, weed control and fertilizer application followed the agricultural practices of the area.

At maize maturity a central square of 1.5 m x 0.75 m was harvested from each microplot, threshed on plant components (grain, and rest of aerial biomass), dried, weighed and ground. All samples were analysed for total N and ¹⁵N concentration, as described by Gabriel and Quemada [1]. For each microplot, plant N uptake (N_t) and labelled-fertilizer recovery (NR) were calculated for each plant component, and added up to obtain values for the whole plant. The NR from fertiliser was calculated as the percentage of total plant N derived from ¹⁵N fertiliser (NRF=100·NR/N_t). The N from other sources (NOS) was calculated as the difference between N_t and NR.

Soil samples to a depth of 0-1 m at 0.2 m intervals were also collected from all microplots at maize sowing and harvest, with an Eijkkelkamp® helicoidal auger as described by Gabriel and Quemada [1]. Control soil samples without labeled fertiliser were also collected. Subsamples were taken for determination of total N and ¹⁵N concentration. Soil N content and NR were calculated for each layer.

## Results

The barley covered faster the soil than the vetch, but differences disappeared during the winter and the vetch covered the ground better than the barley by the time of cover crop killing, including N uptake and biomass differences. Maize biomass and yield were not affected by treatment, averaging 13.8 Mg ha⁻¹ of grain, but N content was. The maize after the vetch uptake 264 kg N ha⁻¹ in the total aerial biomass. After barley and fallow took up only 192 and 228 kg N ha⁻¹ respectively. The N harvest index remained constant for all treatments but not during years (around 0.68 and 0.75 kg N grain per kg N total aerial biomass during 2013 and 2014, respectively). The maize after vetch also increased the N concentration in the grain respect to the fallow.
low and barley (13.1 g N kg⁻¹ versus 11.6 and 10.6, respectively) and in the remaining aerial biomass (5.4 g N kg⁻¹ versus 5.0 and 4.5, respectively).

The NRF was the same for all treatments, averaging 62.3 and 70.6% in 2013 and 2014 respectively. More ¹⁵N was recovered in the grain both years than in the rest of the aerial biomass (51.9 and 68.8 kg N ha⁻¹, during 2013 and 2014 respectively, versus 28.5 and 23.0), but there were no differences between treatments. Differences between treatments in N uptake appeared then because NOS. Maize from the vetch treatment uptake on average 68 kg NOS ha⁻¹ more than the barley and 38 more than the fallow. Cover crop aerial biomass and N uptake were not related with NOS, being in this case a bad indicator for estimating possible fertiliser reduction.

The amount of NRF in the soil after maize harvest did not differ between years or treatments. In all cases it was around 42 kg N ha⁻¹ (equivalent to 32% of the fertilizer applied) with the same distribution by layers between treatments and years. Only during 2014 in the 20-cm upper layer after barley there was a NRF increment. Most of the NRF in the soil profile was found in the upper 40-cm layer (from 65.9 to 84.6%) and only small fraction below 80-cm (from 3.5 to 11.7%). Combining ¹⁵N recovered in the maize biomass and in the soil, the estimated direct losses from the fertilizer were in the order of 5 kg N ha⁻¹ with no differences at 0.95 between treatments or years.

The $N_{min}$ profiles showed that barley reduced $N_{min}$, but these differences disappeared after maize. Moreover, the vetch increased apparent N mineralisation (42 kg N ha⁻¹ with respect to the fallow treatment, with the barley in between), difference sometimes larger than the N content of the cover crop residue.

## Conclusions

Reducing N fertilization led to low soil available N throughout the experiment, enhancing N fertilizer use efficiency and controlling losses. But it also increased the risk of pre-emptive competition with the subsequent cash crop, mostly after the barley and the fallow. In these conditions, cover crops affected N uptake (mostly in the grain N content and higher after vetch and lower after barley), but did not have an effect on the subsequent yield, biomass or C/N translocation to grain.

The low N fertiliser supplied allowed a high NRF, averaging 66.5%. There were no differences between treatments, even when the legume incorporated atmospheric N₂ fixation into the system. Soil ¹⁵N recovery was mostly retained in the upper layers (suggesting that the ¹⁵N was substituting ¹⁴N in a fairly stable organic fraction) and was the same in all treatments. Only during 2014, there was an increase at the 0-20 cm in the fertiliser recovered in the barley treatment, probably due to immobilization. $N_{min}$ profiles after maize growth were low for all treatments, but barley also increased pre-emptive competition reducing $N_{min}$ content before maize planting, without affecting NRF. The capacity of the soils to supply N presented a cumulative effect after seven years of cover cropping.

## Acknowledgements

Spanish Ministry (IJCI-2014-20175, AGL2014-52310-R) and Comunidad de Madrid (S2013/ABI-2717)

## References

[1] Gabriel, J.L., Quemada, M. 2011. Eur. J. Agron. 34, 133-143
EFFECTS OF MYCORRHIZAL INOCULUM AND DIGESTATE FERTILIZATION ON
TRITICALE (×TRITICOSECALE WITTMACK) PRODUCTION USING FUNGICIDES COATED
SEEDS

Caterina Caruso¹, Carmelo Maucieri¹, Antonio C. Barbera², Maurizio Borin¹

¹Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE) - University of Padua, Legnaro (PD), Italy, ²Department of Agriculture, Food and Environment (Di3A) - University of Catania, Catania (CT), Italy

**Objectives**

Fertilization with organic wastes represents an alternative to mineral fertilization for sustainable agriculture [1]. In this context the agricultural reuse of digestate, organic waste products of biogas plants, should be considered. Symbiotic mycorrhizal fungi, such as arbuscular mycorrhizal fungi (AMF), are a significant component of the soil microbial population influencing its fertility, crops yield and ecosystem sustainability with positive roles in the agro-ecosystems such as nutrient mobilization from organic substrates [2]. Fungicides are extensively used in crop system to control fungal phytopathogens, but their application also can affect the soil beneficial microorganisms such as AMF [3]. The aim of the trial was evaluated the effect of AMF inoculation and digestate fertilization on triticale (×Triticosecale Wittmack var. Cosinus) bio-agronomics features and soil CO₂ emission using fungicides coated seeds.

**Method**

The experiment was carried out in 2014-2015 in North-Easter Italy (45°20' N; 11°57' E) in open field conditions adopting a split-plot experimental design. AMF inoculum was the main factor (inoculated (AMF-Y) and not-inoculated (AMF-N)) and fertilization the sub-plots (no fertilization (NF), mineral fertilization (MF), digestate liquid fraction (DL) and digestate solid fraction (DS)) randomly distributed and replicated three times. Each plot had a size of 16 m² (4x4m). DL and DS were supplied before sowing, at rate equivalent to 140 kg N ha⁻¹. Due to their chemical composition, 88 kg K ha⁻¹ and 15 kg P ha⁻¹ and 109 kg K ha⁻¹ and 105 kg P ha⁻¹ were also provided respectively with DL and DS. MF has been distributed in three times: before sowing 40 kg N ha⁻¹, 65 kg K ha⁻¹ and 65 kg P ha⁻¹, after sowing, 50 kg N ha⁻¹ on 20 February and 20 April 2015 were distributed. Triticale was sown on 28 October 2014, at a rate of 220 kg ha⁻¹ seeds coated with fungicides. AMF inoculation, with a commercial inoculum based on *Glomus* spp., was applied at the sowing mixing it with the seeds in the hopper at a dose of 1.2 kg ha⁻¹. On 26 March 2015 a second AMF inoculation was performed at a dose of 1 kg ha⁻¹. During the growing season, soil temperature and moisture in the first 7.5 cm layer and CO₂ emissions were measured seven times (from 78 to 178 days after sowing (DAS)), NDVI index four times (from 143 to 178 DAS) and root percentage AMF colonization [4] three times (from 114 to 222 DAS). Triticale aerial biomass was harvested at dough stage on 8 June 2015 and dry weight was determined at 65°C. Furthermore, at the harvest, shoot stature and shoot density in each sub-plot were detected. Bio-agronomics data were analyzed using ANOVA and the comparison between means was made using Fisher LSD test. Soil CO₂ emission was analyzed with Kruskal-Wallis and Mann-Whitney nonparametric tests. Correlation between soil temperature and moisture with CO₂ emissions were evaluated using Spearman Rank correlation.

**Results**

Root percentage AMF colonization was not significantly different between inoculated and not inoculated plots with values ranged from 0.0% to 11.6% suggesting that inoculation was not effective. Roots colonization could be due to the soil AMF that have been naturally selected over time considering that the soil was managed in the previous years under conventional agronomic techniques using fungicide coated seeds. Among fertilization treatment roots AMF colonization was significant (p<0.05) higher in DS treatment (6.0%) than other ones (1.2%).

AMF inoculation did not show significant effect on monitored bio-agronomic parameters except for shoot density at the harvest time (p<0.05) with higher density in AMF-N (461.3 shoot m⁻²) than AMF-Y (396.0
shoot m⁻²). MF treatment showed a significant (p<0.05) higher plants height (130.2 cm) than NF one (120.2 cm). No significant different plants height was found between DL and DS treatments with an average value of 125.3 cm.

Dry biomass production was significantly (p<0.05) higher in the MF treatment (21.8 ± 1.04 Mg ha⁻¹) compared to DS or DL ones (17.5 ± 1.12 and 16.9 ± 0.64 Mg ha⁻¹, respectively). The lowest dry biomass production (14.5 ± 0.7 Mg ha⁻¹), as expected, was found in sub-plots without fertilization. NDVI index was significantly (p<0.05) influenced by fertilization with the highest value in MF (0.729) and the lowest one in NF (0.551). No significant difference was found between DL and DS plots with an average value of 0.644. No effect was detected for fertilization treatments on soil CO₂ emission with a median value of 447.3 mg m⁻² h⁻¹. In the average of treatments soil CO₂ emissions were positively correlated with soil temperature (Spearman R = 0.617; p<0.001) whereas no correlation was found with soil moisture (Spearman R = -0.015).

Considering that P and K supplied with MF was in the range or lower than DS and DL, the lower yield of these last is probably due to both the N distribution time (all N pre-sowing in DL and DS treatments, in three times in MF treatment) and the lower N fertilization value of digestate (e.g. ammonia volatilization [5]). However, the higher MF biomass production should be considered taking into account the environmental aspects of mineral fertilization. In fact, considering the macronutrients (N, P₂O₅, K₂O) supplied, and using the CO₂₂eq specific emission factors for mineral fertilizers production [6], the indirect emission was +863.8, -674.4 and -1121.2 kg CO₂₂eq ha⁻¹ in MF, DL and DS treatments, respectively.

## Conclusions

Limited effect of AMF inoculation was observed, probably due to seeds coating with fungicides. Although low in absolute value, interesting appears for further research development the colonization capacity of soil AMF because it could be due to naturally selected fungicides resistant AMF. MF determined the highest biomass production (+21% respect digestate treatments), but it should be considered taking into account the environmental (e.g. CO₂₂eq emission) and economical (e.g. fertilizer and distribution costs) aspects. On the basis of the previous considerations, triticale fertilization with digestate can be an interesting alternative in sustainable agriculture. Furthermore, the biomass produced can be used in biogas reactors building a closed cycle. Although results are interesting they were obtained in only one cropping season therefore further experiments are needed.

## Acknowledgment

Research was supported by ValDige project "Valorizzazione del digestato per la riduzione delle perdite di CO₂" DGR n°1604 del 31/07/2012 financed by PSR Regione Veneto (2007-2014) misura 124, Domanda n. 2307827.

## References

[1] Morra, L., Pizzolongo, G., Baiano, S., Pentangelo, A. 2013. Italian Journal of Agronomy, 8(4), 25.

[2] Finlay, R.D. 2008. Journal of experimental botany, 59(5), 1115-1126.

[3] Channabasava, A., Lakshman H.C., Jorquera M.A. 2015. Journal of Soil Science and Plant Nutrition, 15 (1), 35-45

[4] Trouvelot, A. 1986. In: Gianinazzi-Pearson, V., Gianinazzi, S. (Eds.) p. 217-221.

[5] Quakernack, R., Pacholski, A., Techow, A., Herrmann, A., Taube, F., Kage, H. 2012. Agriculture, ecosystems & environment, 160, 66-74.

[6] Capponi, S., Fazio, S., Barbanti, L. 2012. Renewable energy, 37(1), 45-52.
# MANAGEMENT MATTERS: TESTING A MITIGATION STRATEGY OF NITROUS OXIDE EMISSIONS ON MANAGED GRASSLAND

Kathrin Fuchs, Lutz Merbold, Nina Buchmann

ETH Zurich, Zurich, Switzerland

## Objectives

The magnitude of greenhouse gas (GHG) exchange between managed grasslands and the atmosphere largely depends on management practices. While natural or extensively managed grasslands are known to function as GHG sinks intensively managed grasslands are often characterized by substantial nitrous oxide (N₂O) emissions and therefore act as net GHG emitters. One potential approach to mitigate N₂O emissions is a decrease in fertilizer inputs by replacing the needed N input by biological nitrogen fixation via legumes. However, the effect of legumes on nitrous oxide fluxes is still uncertain. In this study we aim at quantifying net GHG fluxes from two management strategies under field conditions in relation to the productivity of the fields (yield estimates). Furthermore, we aim at revealing direct drivers of N₂O exchange and developing suggestions for a more sustainable grassland management in the future.

## Method

We conducted an ecosystem-scale experiment to compare GHG fluxes from an intensively managed Swiss grassland site. The experimental approach consisted of a control parcel representing conventional management with up to 6 harvests and subsequent organic fertilizer application (total N input > 250 kg ha⁻¹) per year as well as an adjacent treatment parcel where common organic fertilizer N inputs are replaced by biological nitrogen fixation via legumes. We measured the net exchange of the three major GHGs, nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂) with the eddy covariance technique in 2015. GHG flux measurements were accompanied by measurements of commonly known driver variables such as water filled pore space, soil temperature, soil oxygen concentrations, pH and mineral N to disentangle the soil meteorological influence of N₂O fluxes from human drivers.

## Results

We measured enlarged peaks in N₂O fluxes emissions following organic fertilizer application in the control site and unchanged N₂O emissions in the treatment site. We observed peaks in N₂O emissions also on the treatment parcel. Mostly these could be attributed to rain events. Net annual fluxes were about one third lower at the experimental parcel. Annual yields were 19% lower at the experimental parcel compared to the control parcel. Relatively dry conditions during the growing season affected plant growth and the timing of the management events.

## Conclusions

Significantly lower nitrous oxide fluxes under experimental management compared to conventional management indicate that nitrous oxide emissions can be effectively reduced at very low costs with a clover-based management. Dry weather conditions are regarded as adequate to reflect future climate at the site. In order to get insights into effects under more common (i.e. wetter) weather conditions, further measurements are required. In addition, implications of the experimental management on animal feed need to be evaluated.
# MODELING WATER-NITROGEN-CARBON FEEDBACKS ON PLANT BIOMASS ACCUMULATION UNDER ELEVATED CO₂ USING A COUPLED HYDROLOGICAL-PLANT GROWTH MODEL

Juliane Kellner¹, Tobias Rütting², Sebastian Multsch¹, Philipp Kraft¹, Lutz Breuer¹

¹Justus-Liebig-University Giessen, Giessen, Germany, ²Göteborgs Universitet, Gothenburg, Sweden

## Objectives

Soil nitrogen and atmospheric carbon dioxide (CO₂) are major variables for potentially enhanced plant growth under climate change. It is hypothesized that increasing CO₂ may work as a fertilizer for crops by increasing biomass production [1]. However, this effect on plant growth can be limited by subsequent nitrogen limitation known as ‘Progressive Nitrogen Limitation hypothesis’ [2]. Coupled models that allow for investigations of the multiple feedback mechanisms between biogeochemistry, plant growth and atmosphere are powerful tools to evaluate hypotheses and to investigate the potential effects of carbon-nitrogen interactions on crops.

We aim at 1) testing and improving the representation of carbon-nitrogen interactions in the coupled hydrological-plant growth model PMF-CMF, 2) investigating the resulting parameter uncertainty. This revised model set up will help to analyse our current system understanding and identify possible missing links in our process representation of the effects of nitrogen supply and elevated CO₂ on biomass accumulation.

## Method

A coupled hydrological-plant growth model using the Catchment Modeling framework (CMF) and the Plant growth Modeling Framework (PMF) will be set up. Both frameworks are flexible and integrative tools, allowing for site specific simulations of plant growth and water transport in the soil [3]. The newest version of PMF includes a response functions of stomatal conductance and biomass accumulation to elevated CO₂, i.e. an increase of atmospheric CO₂ simulates stomatal closure by increasing stomatal resistance and accelerates biomass production by enhancing the radiation use efficiency factor. Nitrogen acquisition is simulated by passive and active uptake, whereby the latter occurs if the passive nitrogen uptake does not match the nitrogen demand. For a reasonable representation of nitrogen-carbon impacts we will test incorporated nitrogen processes and select and implement further crucial processes of the soil nitrogen cycle and link them to effects of elevated CO₂.

The further developed, coupled PMF-CMF model will be confronted with field data of a Free Air Carbon dioxide Enrichment (FACE) experiment, where crops are cultivated in CO₂-emitting rings at different nitrogen fertilization levels. To investigate the parameter space as well as parameter and model uncertainty we will conduct a Monte Carlo based generalized likelihood uncertainty analysis (GLUE) considering RMSE, R² and bias as objective functions using the recently developed SPOTpy package [4]. To increase the performance of Monte Carlo sampling the Latin Hypercube algorithm will be applied.

## Results

First results indicate that hydrological feedback mechanisms of the coupled PMF-CMF model are satisfying. Furthermore, simulations considering the new CO₂ response mechanisms lead to adequate results. Currently, we are testing the new carbon-nitrogen-water feedbacks. We will present the structure of the further developed PMF and show first results of the simulated combined effect of elevated atmospheric carbon dioxide and soil nitrogen availability on biomass. Furthermore, we will show the effect of the model further development on parameter and model uncertainty.

## Conclusions

[1] Ainsworth, E.A., Long, S.P. 2004. New Phytologist. 165, 351–372
[2] Luo, Y., Su, B., Currie, W.S., Dukes, J.S., Finzi, A., Hartwig, U., Hungate, B., Mc Murtrie, R.E., Oren, R., Parton, W.J., Pataki, D.E., Shaw, M.R., Zak, D.R., Field, C.B. 2004. BioScience 54, 731-739

[3] Houska, T., Multsch, S., Kraft, P., Frede, H.-G., Breuer, L. 2014. Biogeosciences, 11, 2069–2082, doi:10.5194/bg-11-2069-2014

[4] Houska, T., Kraft, P., Chamorro-Chavez, A., Breuer, L. 2015. PLOS, DOI: 10.1371/journal.pone.0145180
# NITROGEN EMISSIONS FROM ARABLE LAND WITH DIFFERENT NITROGEN FERTILIZATION

Magdalena Wallman¹, Sofia Delin², Carlo Lammirato³, Per Weslien¹, Leif Klemedtsson¹, Tobias Rütting¹

¹University of Gothenburg, Gothenburg, Sweden, ²Swedish University of Agricultural Sciences, Skara, Sweden, ³YARA GmbH & Co. KG, Dülmen, Germany

## Objectives

Nitrogen (N) losses from fertilization are non-desirable and options for reductions are needed as N losses pose an economic loss for farmers and cause harmful effects to the environment. In order to reduce N losses from arable fields we have to understand the fate of the applied fertilizer. The overall objective of our project is to provide completely closed N budgets for typical Swedish arable fields on clay soil, fertilized with either mineral or organic N fertilizer. The specific aims of the project are:

- Investigate how fertilization rate affect the gaseous and leaching N losses;

- Compare the N flows between treatments with fertilization with biogas residue, more organic rich animal slurry and mineral fertilizer;

- Provide a closed budget for fertilizer N in typical Swedish agricultural conditions.

## Method

The project is conducted at the Lanna Research Station, which is situated on a large agricultural plain in south-western Sweden having a clay soil. Lanna is representative for agricultural crop production on clay soils in Sweden and is the only Northern agricultural ecosystem station within the European GHG network ICOS. We investigate three different rates of mineral N fertilizer (0, 100 and 200 kg N ha⁻¹ yr⁻¹) as well as biogas residues (digested slurry) and animal (pig) slurry (equivalent to 100 kg NH₄⁺-N ha⁻¹ yr⁻¹).

During 2014-16, a range of field flux measurements are conducted in order to quantify three main N loss pathways: leaching losses of nitrate/nitrite and total dissolved N, emissions of nitrous oxide and ammonia volatilization from organic fertilizers. Measurements are conducted on 20 existing leaching plots (20x21m; four per fertilizer treatment) with separate drainage systems supplied with flow-proportional automatic sampling. From these plots, nitrous oxide emissions are permanently monitored using automatic chambers coupled to a laser spectrometer. Ammonia volatilization is measured following fertilization with dynamic chambers.

## Results

The largest N export from the field occurs via crop harvest. Leaching losses showed little variation among treatments, but were 25-40 % higher from plots receiving high mineral fertilizer rate compared to all other treatments. About 10 % of the N applied as pig slurry was lost in the form of ammonia and from the biogas residue about 8 %, which is lower than the typical range reported for animal manure. Nitrous oxide emissions were low from all treatments, ranging between 0.3 and 0.6 kg N ha⁻¹ over the growing season (152 days), suggesting annual losses in the order of 1 - 1.5 kg N ha⁻¹ yr⁻¹. Consequently, the nitrous oxide emission factor (emission divided by applied fertilizer) was in all cases below 1 %, most likely in the range 0.4 - 0.7 %, being lower than the IPCC default value.

## Conclusions

Overall, the fertilized soils, with the exception of low mineral N fertilization, showed preliminary a surplus N balance, while the unfertilized soil showed a negative N balance. However, this N balance so far does not consider N₂ emissions, which will be investigated by ¹⁵N tracer studies for completing the N budget of the arable fields.
Acknowledgments

The project was financial supported by the Swedish Research Council Formas. Additional funding came
from the ICOS infrastructure. We would like to thank the staff at Lanna Research Station for practical assis-
tance with field work.
# SHORT TERM EFFECTS OF POLYACRYLAMIDE AND DICYANDIAMIDE ON C AND N MINERALISATION IN A SANDY LOAM SOIL

Conor Watson¹, Yashneeil Singh¹,², Toufiq Iqbal¹,³, Christoph Knoblauch¹, Peter Simon¹, Florian Wichern¹

¹Rhine-Waal University of Applied Sciences, Kleve, Germany, ²Indian Institute of Technology, Karagphur, India, ³University of Rajshahi, Rajshahi, Bangladesh

## Objectives

The conditioners anionic polyacrylamide (PAM) and dicyandiamide (DCD) are added to soils to respectively reduce soil erosion and nitrogen loss.

Should PAM and residue application improve microbial biomass and conditions, it is possible mineralisation and nitrification activity would increase, in which case simultaneous DCD application could be advantageous in preventing N loss.

A 27-day incubation study was set up to gauge their interactive effects on the microbial biomass, carbon mineralisation and nitrification activity of a sandy loam soil in the presence or absence of maize straw. The objectives were to ascertain whether:

* PAM stimulated the soil decomposition of native and added C residues

* PAM increased soil nitrification when applied with $(NH_4)_2SO_4$ with or without the nitrification inhibitor DCD

* Ammonium sulphate application, with or without DCD, significantly affected the soil microbial biomass

* There are interactive effects of maize straw application and N fertilisation on C mineralisation and the soil microbial biomass

## Method

Soil was collected from the top 30 cm of a maize field, sieved (< 2 mm) and stored at 5° C for one month prior to the experiment beginning. PAM-amended soils received 308 or 615 mg PAM/kg (Stockosorb® 500, Evonik Stockhausen GmbH, Krefeld, Germany), respectively representing 100 or 200 % of the recommended application rate. N-fertilised soils were amended with 1800 mg/kg $(NH_4)_2SO_4$, with or without 70 mg DCD/kg. Maize leaf/stem straw was added to soil at the rate of 4500 mg dry matter/kg.

The incubation experiment took place for 27 days at 22° C with all samples (100 g dry weight) adjusted to 50 % water-holding capacity in 1 L glass jars. All of the following treatments were carried out in replicates of five:

(1) control

(2) ammonium sulphate $(NH_4)_3$

(3) ammonium sulphate plus dicyandiamide $(NH_4)_2SO_4$

(4) 100 % PAM (100 PAM)

(5) 100 % PAM plus $(NH_4)_2SO_4$ (100 PAM, $NH_4$)

(6) 100 % PAM plus $(NH_4)_2SO_4$ + DCD (100 PAM, $NH_4$ + DCD)

(7) 200 % PAM (200 PAM)
$$ (8) \quad 200 \% \text{ PAM plus } (\text{NH}_4)_2\text{SO}_4 \text{ (200 PAM, } \text{NH}_4\text{)} $$

$$ (9) \quad 200 \% \text{ PAM plus } (\text{NH}_4)_2\text{SO}_4 + \text{DCD} \text{ (200 PAM, } \text{NH}_4\text{) + DCD} $$

Evolved CO₂ during the incubation was absorbed in alkali traps containing 1.0 M NaOH solution. Traps were removed from all jars after 2, 5, 12, 20 and 27 days prior to being back titrated with 0.1 M HCl after addition of 5 mL saturated BaCl₂ solution. Quantities of evolved CO₂ were used to calculate cumulated CO₂-C (CC) and the metabolic quotient ($qCO_2$, CO₂-C evolved per unit of microbial biomass C per day).

Microbial biomass C (MBC) was determined by fumigation extraction at the end of the incubation period, while aliquots of the non-fumigated soil extracts being taken for determination of NH₄⁺ and NO₃⁻. At the end of the experiment, subsamples from each jar were refrigerated and later air-dried prior to pH determination.

## Results

Maize straw application increased soil microbial biomass and respiration. PAM stimulated C mineralisation, as evidenced by significant increases in evolved carbon dioxide (CO₂) concentrations. In treatments receiving PAM and NH₄ without DCD, nitrate concentrations were markedly greater, and ammonium concentrations decidedly lower, than in the corresponding treatment without PAM, indicating a stimulation of nitrification by PAM. PAM-stimulated nitrification and C mineralisation are likely to have been effected by the PAM improving microbial conditions (enhanced aeration, water permeability and cationic nutrient retention) and partially being utilised as a substrate, with the latter being indicated by a PAM-induced significant increase in the metabolic quotient. PAM did not reduce the microbial biomass except in one treatment at the highest application rate. Therefore it could have a detrimental effect on soil microbial biomass, despite the normally beneficial effect of residue additions, if PAM has accumulated or is applied excessively.

Ammonium sulphate stimulated nitrification and reduced microbial biomass; the resultant acidification of the former is likely to have caused the latter. The metabolic quotient of the treatments revealed DCD to have caused reduction relative to the control which indicated suppression of nitrifying bacteria. N fertilisation may also have induced short-term C limitation in the soil which impacted on microbial growth and respiration. In our relatively short-term experiment, it is possible the expected stimulatory effect of N addition was dependent on release of C from more recalcitrant components of the native and added residue after exhaustion of easily degradable (soluble) C and was therefore not evident in our results.

The extractable nitrate and ammonium results showed that the DCD in all PAM treatments was effective at inhibiting nitrification and keeping nitrate concentrations lower than those in the control. The nitrification inhibitor DCD reduced the negative impacts on microbial biomass of $(\text{NH}_4)_2\text{SO}_4$. As well as the DCD reducing nitrification and the resultant microbe-stressing acidification, this could also have arisen as a result of preferential bacterial immobilisation of $\text{NH}_4^+$ to $\text{NO}_3^-$.

## Conclusions

In our 27-day incubation experiment, soil C mineralisation rates proved to be stimulated by PAM addition. This arose as a combination of improved microbial conditions and PAM partially being utilised as a microbial substrate. PAM also stimulated nitrification when applied with $(\text{NH}_4)_2\text{SO}_4$; this effect could be nullified with concurrent DCD application. Ammonium sulphate application had negative impacts on microbial biomass C. This effect arose due to soil acidification following nitrification and was reduced with simultaneous DCD application. Maize straw application increased soil microbial biomass C but this increase was not as marked if applied with N fertilisers or excessive amounts of PAM. This was probably a short-term C-limitation effect following exhaustion of easily degradable C. DCD is an effective soil amendment to reduce nitrification under conditions where mineralisation is increased by addition of PAM and/or residue incorporation. Therefore concurrent PAM and DCD application is recommended in nitrate vulnerable zones where erosion-threatening soils are amended with fertilisers or manures.
Acknowledgements

This project was supported by a grant of the Rhine-Waal University of Applied Sciences. We are grateful to
Julia Gorris, Sanja Schwalb, Axel Hinnemann and Karla Kaminski for technical assistance.
CAN NITRIFICATION INHIBITORS AND MANURE TMING IMPACT NITROUS OXIDE EMISSIONS FOLLOWING FIELD INJECTION OF LIQUID MANURE?

Sisi Lin¹, Guillermo Hernandez-Ramirez¹, Len Kryzanowski², Trevor Wallace², Robert Grant¹, Rory Degenhardt³, Nils Berger⁴, Germar Lohstraeter², Leigh-Anne Powers²

¹Department of Renewable Resources, University of Alberta, Edmonton, Canada, ²Alberta Agriculture and Forestry, Edmonton, Canada, ³Dow AgroSciences, Edmonton, Canada, ⁴Eurochem Agro, Mannheim, Germany

**Objectives**

The main objective of this research was to investigate nitrous oxide (N₂O) emission reduction strategies in an annual cropping system receiving the liquid manure application. This research compared N₂O emissions from two contrasting manure injection times (fall vs. spring), examined the effectiveness of nitrapyrin and 3, 4-dimethylpyrazole phosphate (DMPP) and identified the key biophysical controls on N₂O flux in Alberta cropping systems.

**Method**

From fall 2014 to fall 2015, two split-plot field experiments were initiated in Alberta, Canada (Edmonton and Lacombe sites). Liquid manure (dairy or swine) was injected with or without nitrification inhibitors (nitrapyrin and DMPP). N₂O flux measurements, soil temperature, soil water content as well as plant aboveground biomass and N uptake were measured following the fall and spring manure injections. Field flux measurements were done during the frost free periods using manual static chambers (weekly or twice per week following major rainfall or manure injection). Composite (at least 3) disturbed soil samples were collected after manure injections and some of them were collected by the band and inter-band area separately when necessary.

**Results**

At both sites, the amount of annual cumulative N₂O emissions generated from the fall manure without NIs was about two times than that from the spring manure without NIs. This differential N usage derived from the timing of manure injection was also observed in the crop N uptake in Lacombe. The N uptake in the spring-manured only treatment was significantly higher than the fall-manured only. All manure injections resulted in a significant increase in N₂O emissions compared to the controls without manure (Ps < 0.05). The increasing N₂O emissions from manure applications could be reduced by incorporating the NIs. At the Lacombe site, fall-applied DMPP and nitrapyrin reduced by 81.0 and 57.8% annual total N₂O emissions compared to the treatment with manure without NIs. These reductions by NIs were also observed for spring-applied DMPP and nitrapyrin treatments but they were less pronounced. For the fall-manured soils, more than 67% of annual cumulative N₂O emissions were derived from the emissions observed during the early spring after snow-melt and soil thawing. In addition, the annual N₂O emissions from either fall-manured or spring-manured soils without NIs in Lacombe were about triple than that in Edmonton. This was likely due to the drier soil condition in Edmonton than Lacombe.

**Conclusions**

The spring manure injection could become a N₂O mitigation strategy in the areas with similar climatic and edaphic conditions as Alberta, Canada; because the spring manure injection resulted in lower annual N₂O emissions and higher crop N uptake than the fall manure injection. Nitrification inhibitors could reduce N₂O emissions associated with liquid manure application. With respect to the N₂O reduction results, DMPP was more efficient than nitrapyrin. The performance of inhibitors, however, might be restricted under a dry season or soil condition. Additional studies are recommended to address knowledge gaps such as the impacts by different levels of soil moisture content and temperature on NIs effectiveness. It appears that soil moisture content could be the key driver for the N₂O emissions as evidenced by the peak N₂O emissions following the snow-melt in the early spring and the lower annual N₂O emissions in the Edmonton site.
EFFECTIVENESS OF NITRIFICATION INHIBITORS AND CONTRAST OF FIELD VERSUS INCUBATION EXPERIMENTS ON SOIL NITROGEN KINETICS AND NITROUS OXIDE EMISSIONS

Sisi Lin¹, Guillermo Hernandez-Ramirez¹, Len Kryzanowski², Trevor Wallace², Robert Grant¹, Rory Degenhardt³, Nils Berger⁴, Germar Lohstraeter², Leigh-Anne Powers²

¹Department of Renewable Resources, University of Alberta, Edmonton, Canada, ²Alberta Agriculture and Forestry, Edmonton, Canada, ³Dow AgroSciences, Edmonton, Canada, ⁴Eurochem Agro, Mannheim, Germany

**Objectives**

The main objectives of this study are to evaluate the potential amount of nitrous oxide (N₂O) emissions reduced by nitrification inhibitors, to contrast the effectiveness of the nitrification inhibitors, to examine how well the N₂O production measurements in the laboratory incubation compare to the N₂O in the field, and to assess the first- and second-order kinetic models in describing the soil mineral N transformations.

**Method**

The soil sampling site was located in Edmonton, Alberta. The liquid dairy manure was applied in the early fall of 2014 and in the spring of 2015 with a rate of 74.14 m³ ha⁻¹. Two types of nitrification inhibitors were used in this project --- nitrapyrin and 3, 4-dimethylpyrazole phosphate (DMPP). They were independently mixed with the manure at a rate of 0.5 kg a.i. ha⁻¹. Seven treatments were conducted in this project, including control with the manure injector disturbance (CT), fall manure without any inhibitors (FW), fall manure with DMPP (FD), fall manure with nitrapyrin (FN), spring manure without any inhibitors (SW), spring manure with DMPP (SD) and spring manure with nitrapyrin (SN). Flux measurements were conducted both in fields and in a laboratory incubation (28 days). Composite disturbed soil samples for the incubation were all collected one day after the spring manure injection in the same manner. Band and interband soil samples were collected from SD, SN, SW and CT treatments. Field flux measurements were done using manual static chambers (weekly or twice per week following major rainfalls or manure injections). The incubation gas production measurements were done by using mason jars with a rubber septum. The frequency was twice a week during the first two weeks of the incubation, and once a week for the following three weeks. Soil ammonium and nitrate were analyzed once a week throughout the incubation.

**Results**

For the spring manure treatments, the manure with DMPP and nitrapyrin reduced cumulative N₂O flux by 32% and 42%, respectively, compared to the treatment with manure only in the incubation. However, the inhibitors did not reduce soil N₂O production in the fall manure treatments. The highest cumulative N₂O flux was for the fall manure with DMPP treatment (0.31 kg N ha⁻¹). This is because the N retained by the DMPP since the fall was rapidly transformed leading to intense N₂O production once the soil with the fall DMPP additive was incubated under optimal conditions [i.e., temperature of 20.4°C and 60% water-filled pore space (WPFS)]. In addition, a remarkably higher cumulative N₂O fluxes happened in the spring manure band soils. This clear spatial banding effect can be directly explained because the band zones had significantly higher initial NH₄⁺-N and NO₃⁻-N concentrations. The difference in N₂O emissions between the incubation and the field was compared. For the fall treatments and the control treatment, the N₂O output in the incubation has the same sequence of that in the field but it had much higher N₂O emissions compared to the field. This is because both the temperature and the volumetric water content in the incubation were higher than those in the field, stimulating the activities of denitrifiers and nitrifiers. The increased N₂O emissions in the incubation for the fall-manured and control treatments were also observed after accounting for the effect of temperature by normalizing the cumulative N₂O production based on thermal time. This result showed that the soil moisture content was the key driver to the N₂O production in the incubation. However, the incubation N₂O production result was lower than in the field for the spring-manured treatments. This might be due to the disturbance of aggregates when field sampling and manipulating the soils and establishing the laboratory incubation. Compared to the first-order kinetic model, the second-order model in general could better
describe faster soil ammonium transformations as shown by lower p-values and higher R² values.

## Conclusions

Both types of nitrification inhibitors reduced N₂O emissions. Compared to the nitrapyrin, DMPP seemed to be more effective when applied at the same active ingredient rate. Both high concentration of substrates and high soil water content could potentially produce high N₂O emissions. It can be noted that the disturbance of soil aggregates could lead to underestimation the amount of N₂O produced in laboratory incubation in particular for the recently-manured soils. Rapid ammonium transformations in soils can be better described by the second-order kinetic model compared to the first-order model.
# DEPOLYMERIZATION AND MINERALIZATION - INVESTIGATING THE RATE LIMITING STEP BY A NOVEL ¹⁵N TRACING MODEL

Louise C. Andresen¹, Anna-Karin Björsne¹, Samuel Bodé², Leif Klemedtsson¹, Pascal Boeckx², Tobias Rüt-
ting¹

¹University of Gothenburg, Gothenburg, Sweden, ²Ghent University, Ghent, Belgium

## Objectives

Depolymerization of soil organic matter (such as proteins and peptides) into monomers (e.g. amino acids) is currently thought to be the rate limiting step for the terrestrial N cycle. The production of free amino acids (FAA) is followed by FAA mineralization, which is an important fraction of the total N mineralization. Accurate assessment of depolymerization and FAA mineralization rates is important to gain a better understanding of the N cycle dynamics.

## Method

We combine for the first time two parallel ¹⁵N tracing experiments, in which soil is separately amended with ¹⁵N labelled ammonium or an amino acid mixture. For data analysis, we further developed the numerical ¹⁵N tracing model Ntrace to explicitly account for FAA turnover, in order to simultaneously quantify gross depolymerization, gross FAA mineralization and total gross N mineralization in forest soils. With this approach a more robust and coherent rate assessment and a more accurate calculation of microbial amino acid nutrient use efficiency (NUEFAA) is achieved. Soil was sampled from two forests at the Skogaryd Research Catchment (SITES; Swedish Infrastructure for Ecosystem Studies, www.feldsites.se), situated in southwest Sweden (58° 23'N, 12° 09'E; 60 m above sea level).

## Results

We present an extended numerical ¹⁵N tracing model Ntrace which incorporates the FAA pool and related N processes to 1) provide a more robust and coherent estimation of production and mineralization rates of FAAs; 2) expand the experimental time-frame to get more realistic FAA mineralization rates; and 3) suggest a realistic microbial N use efficiency of amino acids (NUE<sub>FAA</sub>) in soils.

## Conclusions

We compare analytical and numerical approaches for two forest soils, suggest improvements of the experimental work for future studies and conclude that: i) FAA mineralization might be an equally important limiting step for gross N mineralization to depolymerization, because about half of all depolymerized N is further mineralized; and that ii) FAA mineralization and FAA immobilization rates should be used for assessing NUE<sub>FAA</sub>.
RESIDUAL EFFECT OF DIFFERENT NITROGEN FERTILIZATION ON REED CANARY
GRASS, (PHALARIS ARUNDINACEA L.) IN MONOCULTURE AND IN MIXTURE WITH
GOAT'S RUE, (GALEGA ORIENTALIS, LAM.)

Cecilia Palmborg

Swedish University of Agricultural Sciences, Umeå, Sweden

Objectives

Reed canary grass (RCG) harvested in spring is a potential energy carrier as a solid fuel or as a feed stock for biogas production. The RCG also has a potential as a recipient crop for municipal residues such as sewage sludge and ash from incineration of biofuels. Previous studies have shown no or small differences between fertilization treatments for RCG in monocultures or intercropped with legumes [1]. This study was conducted to further investigate the impacts of fertilizing regimes for these crops. The main questions asked were: What are the effects on harvest and lodging of omission of nitrogen fertilization on biomass production and the competition between reed canary grass and goat's rue in the intercrop? Can sewage sludge pellets replace mineral fertilizers as a nitrogen source?

Method

The experiment was established in Ås in Jämtland in 2008 on moraine clay (clay 19 %). It was designed to study reed canary grass/legume intercrops under different fertilization regimes for three production years (2009-2011) before this extra experiment was conducted 2012. The original experiment was a split plot experiment with three fertilization treatments (A) Full NK fertilization (average 70 kg N ha-1), B) half N plus K (average 35 kg N ha-1), or C) half N (average 35 kg N ha-1) plus sewage sludge (1200 kg=35 kg N ha-1) on the main plots and the different species mixtures as sub plots. N fertilization was used in the intercrops as a means to control the legume content by increasing RCG biomass. In the current experiment, conducted 2012, plots with either monoculture RCG, established together with barley or as sole crop or RCG intercropped with goat's rue where two different sowing densities of goat's rue were used. Goat's rue was used since it has been successfully intercropped with RCG in i.e. [2]. There were no significant differences related to establishment technique after the first harvest year. Further details are found in Lindvall et al. [1]. Two plots with the same species composition in each main plot were randomly assigned to either continuation of the previous fertilization treatment or omission of the mineral N and NK fertilization. The N-fertilization treatments (A1) 60 kg N ha-1) B1) 30 kg N ha-1, C1) 30 kg N ha-1 + 35 kg N ha-1 as sewage sludge, A0) and B0) no fertilization and C0) 35 kg N ha-1 as sewage sludge) were conducted on four plots of reed canary grass monoculture and four plots of reed canary grass/goat's rue intercrop. The botanical composition was assessed by sorting biomass from 50*50 cm subplots in August to sown species plus weeds. Lodging was graded before harvest. The plots were harvested by a Haldrup harvester in September 6 2012. Dry matter content was determined by drying subsamples in 60oC. The NCSS general linear model ANOVA and Dunnet's one sided tests were used for statistical analysis.

Results

The ANOVAs (treatment factors; previous fertilization (main plot), N or not 2012, and species mixture, were included in the model as fixed factors and block was random factor)
showed that RCG/goat's rue intercrop had a higher autumn yield (9943 kg DW ha-1) and less weeds (6%)
than the monoculture RCG, (8679 kg DW ha-1 and 16% weeds). It showed no significant differences in yield or proportion of goat's rue due to fertilization treatments either in the year of the extra experiment or the previous years. However, Dunnet's one sided test showed that the B treatment had a lower yield (8679 kg DW ha-1) and that the C treatment had a higher proportion of goat's rue (41%) than the fully fertilized control (9750 kg DW ha-1 and 28% goats rue). It is motivated to use a one sided test since it can be expected that N-fertilization increases yield and decreases legume proportion. However, the intercrop was lodging (only 10% standing up), compared to 74% in the monoculture RCG. Omission of N-fertilization a single year had no significant effects at all.

Grass/legume intercrops often are more productive than monocultures of the included species.in RCG/goat's
rue this has been shown by [2]. One difficulty with intercrops is to achieve a predictable proportion of the different species. When reed canary grass is harvested for combustion is it most often done in spring. Then it is an advantage to have a low proportion of legumes because legumes are more easily decomposed during the winter [3]. In the widely used intercrop between grass and clover for forage it is possible to control the proportion of clovers by nitrogen fertilization. We show here that N-fertilization can control the amount of goat's rue in the intercrop to some extent, but not enough to prevent disadvantages such as lodging. The higher yield in the intercrop, probably due to N-fixation of the goat's rue symbionts, is also not enough to compensate for extra costs of sowing and decomposition losses during winter.

Reed canary grass is previously shown to be dependent of N-fertilization. It is shown that a high N-fertilization leads to a higher allocation of both carbon and nitrogen to the rhizomes during winter [4, 5]. It has been assumed that this is beneficial for the biomass growth next spring. This study shows that the present N fertilization recommendations for RCG are probably too high since the lower N-fertilization level has only a small yield penalty. It is possible to omit mineral N fertilization for a single year and it is also possible to supply part of the N-requirement of the grass with organic sources like sewage sludge pellets.

## Conclusions

In a spring harvest system with reed canary grass, where leached, nutrient poor biomass is removed from the field, it is possible to omit N-fertilization for a single year without yield penalties or effects on the botanical composition of reed canary grass/goats rue intercrop. There is a small negative effect of cutting of N-fertilization in half. Sewage sludge can be used to replace at least half of the N-fertilization without yield penalties.

## Acknowledgement

This study was financed by Formas and The Swedish Energy Board. Also thanks to Eva Lindvall and the skillful field staff at Torsta: Per-Erik Nemby and Boel Grufberg.

## References

[1] Lindvall, E., Gustavsson, A.-M. Palmborg, C. 2012. Global Change Biology Bioenergy 4. p. 661-670.

[2] Jasinskas, A., Zaltauskas, A. Kryzeuiciene, A. 2008. Biomass & Bioenergy 32. p. 981-987.

[3] Lindvall, E., 2014, Thesis, Swedish University of Agricultural Sciences: Umeå, Sweden. p. 53.

[4] Xiong, S. and Kätterer, T. 2010. Acta Agriculturae Scandinavica. Section B, Plant Soil Science 60. p. 24-32.

[5] Xiong, S., Landström, S. Olsson, R. 2009. Acta Agricultura Scandinavica. Section B, Plant Soil Science, 59. p. 306-316
# EFFECT OF DIGESTATE SOLID FRACTION ON HORTICULTURE SUCCESSION YIELD AND SOIL CARBON DIOXIDE EMISSION

Carmelo Maucieri, Carlo Nicoletto, Caterina Caruso, Paolo Sambo, Maurizio Borin

Department of Agronomy, Food, Natural Resources, Animals and Environment (DAFNAE) - University of Padua, Legnaro (PD), Italy

## Objectives

The biomass anaerobic digestion for biogas production is one of the most widespread renewable energy form. However, together with biogas, anaerobic digestion produces a residual material (digestate) that considering its composition could be used in agriculture as fertilizer [1] if certain quality characteristics such as stability and hygiene are satisfied. Such organic matrix could then represent a good alternative to the use of mineral fertilizers determining both indirect reduction of CO₂ emission in atmosphere and improve of the soil physico-chemical properties, with environmental positive impact.

The aim of this study was to evaluate the environmental and production aspects of digestate solid fraction (DSF) use in a one-year horticultural succession.

## Method

The trial was carried out at the Experimental Farm of Padua University at Legnaro, North-East Italy (45°20' N; 11°57' E) in open field conditions using DSF on green bean, savoy cabbage, cabbage and cauliflower. Three fertilization treatments were tested using DSF to substitute mineral N crop requirements: 1) 50% N through DSF and 50% N through mineral fertilizer (T50); 2) 100% N through DSF (T100); 3) 100% mineral fertilization (Tmin). The P and K content in the DSF were taken into consideration to calculate the amount of these elements to supply in the different treatments. Fertilization was supplied according to standard recommendations in the area: 40, 50, 100 kg ha⁻¹ for green bean and 110, 70, 160 kg ha⁻¹ for the other species respectively for N, P₂O₅ and K₂O. Both mineral and DSF was supplied from 1 to 4 days before sowing or transplanting and immediately incorporated by rotavator. The soil had a loamy texture. A randomized block experimental design with three replications was used with plots of 40 m². The green bean was sowed on 22 May 2014 and harvested on 14 July 2014, savoy cabbage was transplanted on 12 August 2014 and harvested on 15 January 2014. After, each plot was split into two subplots of 20 m² and both cabbage and cauliflower were together grown transplanting them on 3 April 2015. Cauliflower was harvested on 27 May 2015 and the cabbage on 3 June 2015. Crops were harvested at full crop marketable maturity. For each plot, five plants were cut into small pieces and dried in a ventilated oven at 65°C to calculate the dry matter content. In this last, the total Kjeldahl nitrogen (TKN) content was determined. During crops growing season the soil CO₂ emissions were measured two times per week in two points for each plot using the static non-stationary chamber technique. For savoy cabbage soil CO₂ emissions were not detected from half October till the first week of December. In each CO₂ measurement point, soil temperature and moisture (TDR 100 Soil Moisture Meter) in the first 7.5 cm were also detected.

## Results

The crops yield was not significantly influenced by the fertilization treatments with an average (±SE) marketable yield of 9.0 ± 0.5, 9.9 ± 1.2 and 51.3 ± 6.4 Mg ha⁻¹ for green bean, cauliflower and cabbage, respectively. The savoy cabbage marketable yield was significantly (ANOVA, p<0.05) higher in the Tmin treatment (25.9±1.0 Mg ha⁻¹) than T100 one (16.8 ± 2.7 Mg ha⁻¹); T50 was not significantly different between the previous two treatments (20.8 ± 2.3 Mg ha⁻¹). The lower production with DSF probably due to the low environmental temperatures that reduced soil microbial activity, with a consequent reduction of the nutrients availability by the digestate. With respect to the TKN biomass content, no significant differences were observed in relation to fertilization treatments for green bean, cauliflower and savoy cabbage with an average value of 2.89%. Cabbage showed a significant (ANOVA, p<0.05) lower TKN concentration in the biomass of T100 treatment (1.80%) than the other ones (2.26%). Among species the significant higher and lower
TKN concentration were showed by cauliflower (3.40%) and cabbage (2.10%), respectively. No significant difference was found between green bean and savoy cabbage with an average value of 2.61%. Fertilization treatment did not exert significant effect on N uptake whereas, as expected, significant (ANOVA, p<0.05) different N uptake was found among plant species with greater values for cabbage and savoy cabbage (average value of 70.5 ± 6.3 kg N ha⁻¹) than green bean and cauliflower (average value of 21.1 ± 1.4 kg N ha⁻¹). Considering the percentage N recovery with marketable biomass respect the N supplied it was not significant different among fertilization treatments with an average value of 58.3%, 45.9% and 42.7% for Tmin, T50 and T100, respectively.

The soil CO₂ emissions were not significantly different, for each crop, between fertilization treatments with median value always below 1 g m⁻² h⁻¹. In the average of crops species the soil CO₂ emissions were positively correlated with soil temperature (Spearman rank 0.214, p<0.001) and moisture (Spearman rank 0.207, p<0.001). Considering the climate changes the environmental impact of productions and so of fertilization is of increasing interest. Therefore, the indirectly reduction of greenhouse gases emission in the atmosphere plays an important role. In our experiment, considering only the DSF and mineral fertilizers macronutrients (N, P₂O₅, K₂O), and using the CO₂eq specific emission factors for mineral fertilizers production [2], the carbon emissions in the atmosphere were equivalent for: 1) green bean at 371.9, 50.9, -233.2 kg CO₂ ha⁻¹ for Tmin, T50 and T100, respectively; 2) savoy cabbage at 724.9, -109.4, -803.4 kg CO₂eq ha⁻¹ for Tmin, T50 and T100, respectively; 3) cabbage and cauliflower at 724.9, -55.4, -694.9 kg CO₂eq ha⁻¹ for Tmin, T50 and T100, respectively.

## Conclusions

Results showed that the use of DSF in a horticultural crop succession, alone or in combination with chemical fertilization: 1) did not show significantly different production than that obtained with only mineral fertilization in bean, cabbage and cauliflower; 2) showed a significantly lower production in winter crop, probably due to the low environmental temperatures that reduced soil microbial activity, with a consequent reduction of the nutrients availability by the DSF; 3) did not significantly influence the TKN concentration, N uptake and N recovery in the marketable biomass; 4) did not show different soil CO₂ emissions than those monitored with only chemical fertilization; 5) thus showing an indirect reduction of CO₂ emissions when used as substitute of chemical fertilization.

## Acknowledgment

The research was supported by ValDige project "Valorizzazione del digestato per la riduzione delle perdite di CO2" DGR n°1604 del 31/07/2012 financed by PSR Regione Veneto (2007-2014) misura 124, Domanda n. 2307827.

## References

[1] Nicoletto, C., Santagata, S., Zanin, G., Sambo, P. 2014. Scientia Horticulturae, 180, 207-213.

[2] Capponi, S., Fazio, S., Barbanti, L. 2012. Renewable energy, 37(1), 45-52.
# IMPROVEMENT OF WINE TERROIR MANAGEMENT ACCORDING TO BIOGEOCHEMICAL CYCLE OF NITROGEN IN SOIL

Najat NASSR¹, Aude LANGENFELD¹, Mohammed BENDRAHIM¹, Lionel LEY², Laurent DELIERE³, David LAFOND⁴, Marie THIOLLET-SCHOLTUS²

¹RITTMO Agroenvironnement, Colmar, France, ²INRA, Colmar, France, ³INRA, Villenave d'Ornon, France,

⁴IFV, Beaucouze, France

## Objectives

Good yield wine production implies well-balanced BCN (biogeochemical cycle of nitrogen), in soil and plant [1]. Nitrogen is very important for grape quality and soil sustainability. The mineralization of organic nitrogen, depending on soil microbial activity, which is linked to soil cover crop management, is the main source of mineral nitrogen for the vine [2][3][4][5]. This study is focused on the microbial functional populations implicated in the BCN, in particular nitrifying bacteria.

## Method

Experimental network has been set up since 2012, with 6 vine sites located France by the Atlantic coast (Loire valley: two integrated systems, Loamy, sandy and clayey soil / Bordeaux: organic and integrated systems, Sandy soil) and in North-East (Ribeauvillé-Alsace organic and integrated systems, Loam, sandy and clayey soil / Rouffach-Alsace, two integrated systems, Loam, sandy and clayey soil / Ingersheim-Alsace organic, Sandy loam soil / Chatenois-Alsace organic, Sandy loam soil). These vine sites represent a diversity of environmental factors (i.e. soil and climate) combined to terroir management. These 6 sites represent 11 sites-systems with different management (soil, pesticides' input and terroir management). Studied systems are either integrated or organic. All systems are innovative and deal with low or very low pesticides inputs.

The approach consists in measuring biological and chemical indicators to assess nitrogen dynamic in soil, i.e. nitrogen mineralization, microbial biomass and activity. Soil microbial communities (bacteria and fungi) are studied with quantitative PCR (Polymerase Chain Reaction) measures targeting 16S (bacteria) and 18S (fungi) DNA. The metabolic functional diversity of cultivable bacteria is determined using Biolog® Ecoplates systems with 31 carbon and nitrogen substrates. Potential nitrogen mineralization is evaluated in microcosm incubation with control condition (temperature and moisture used for soil incubation are those proposed by standard ISO 14238).

In 2014 and 2015, soils were sampled in triplicates at 3 dates: bud break - veraison - leaf fall. Statistical analyses (using Statgraphics) are performed to determine the relationship between biological indicator and nitrogen mineralisation regarding farmer's practices.

## Results

In 2014 and 2015, for Alsacian sites (6 sites/systems), organic systems present higher values of functional richness than for integrated ones, this is particularly observed at bud break, even if it is not confirmed by significant statistical test. This effect is observed in the two studied years 2014 and 2015. Bacterial abundance measured in Ribeauvillé by qPCR show higher bacterial biomass in organic system than in integrated one, especially at bud break. Stimulation of bacterial activity (functional richness) is also observed for organic system. In Chatenois and Ingersheim, high functional diversity and high bacterial biomasses are measured for these two sites, at all dates of measure. This may be explained by organic farming since more than 10 years on these sites while others sites are organic for shorter periods (less than 10 years).

In 2014, higher functional diversity is measured for integrated system in Bordeaux at bud break. This difference is not observed anymore after that date. Lower bacterial abundance is observed for integrated system
at veraison in Bordeaux both in 2014 (strong effect) and in 2015 (tendency). In Loire valley, there's no difference on functional diversity between organic and integrated systems.

No difference is observed on the soil organic nitrogen content in Atlantic coast sites according to the terroir managements. However, significant differences are observed in the Alsace sites with higher soil organic nitrogen in integrated systems. Nitrogen mineralization kinetic is measured for 90 days. Results are used to model mineralization in all soils depending on time. For Alsace sites, the highest mineralization rate is observed for integrated system in Ribeauvillé and the lowest rates for Ribeauvillé-organic and Rouffach-integrated.

For the Atlantic coast, Loire valley sites have higher mineralization rates than Bordeaux ones in 2014, but this effect is not maintained in 2015. In addition, practice management affect rate of nitrogen mineralization in the Bordeaux sites-systems. However, this is observed only in 2015 when nitrogen mineralization is higher comparatively to 2014. These results indicate that practice managements affect net mineralization of nitrogen but this effect seems to be less pronounced than the effect of environmental factors.

To study how technical management of the sites-systems explain measured parameters (soil mineralization, soil microbial populations, physico-chemical parameters of soil), a Principal Component Analysis is performed. This analysis highlights a strong effect of environmental factors on measured parameters as figures are grouped by sites. However, type of systems also influenced our results: Alsace and Loire valley sites are grouped depending on type of systems. This is not observed for Bordeaux sites, but the type of soil (sandy) has a great influence especially on mineralization parameters. Furthermore, this site is also the youngest vine (3 years).

## Conclusions

The sites-systems studied showed effect of farming practices (Integrated or Biological) on measures of bacterial abundance (qPCR), of bacterial functional diversity (Biolog® Ecoplates) and of nitrogen dynamic. This is observed even if an effect of environmental factors on microbial indicators is observed. These BCN indicators can be combined to differentiate between sites-systems according to practice managements. These indicators could help in managing nitrogen dynamics and nitrogenous nutrition of vine in innovative sites/ systems with various practice management.

## References

[1] Guilpart, N., Metay, A., and Gary, C. 2014. European Journal of Agronomy 54, 9-20.

[2] Barlow, K., Bond, W., Holzapfel, B., Smith, J., and Hutton, R. 2009. Australian Journal of Grape and Wine Research 15, 131-143.

[3] Ingels, C. A., Scow, K. M., Whisson, D. A., and Drenovsky, R. E. 2005. American Journal of Enology and Viticulture 56, 19-29.

[4] Raath, P. J., and Saayman, D. 1995. South African Journal of Enology and Viticulture 16, 7-13.

[5] Thiebeau, P., Herre, C., Doledec, A. F., Perraud, A., Panigai, L., Mary, B., and Nicolardot, B. 2005. Journal International Des Sciences De La Vigne Et Du Vin 39, 163-177.
# MICROBIAL NITROGEN RECYCLING IN AGRICULTURAL SOIL - DOES FERTILISATION WEAKEN DISSIMILATORY NITRATE REDUCTION TO AMMONIUM?

Philipp Schleusner¹, Martina Putz², Sara Hallin², Tobias Rütting¹

¹University of Gothenburg, Gothenburg, Västra Götaland, Sweden, ²Swedish University of Agricultural Sciences, Uppsala, Uppsala län, Sweden

## Objectives

A large excess of mineral nitrogen (N) in European agriculture is causing harmful consequences to the environment [1]. The mineral N compound nitrate can be reduced by two dissimilatory soil processes: (i) denitrification, the stepwise reduction to atmospheric dinitrogen, and (ii) dissimilatory nitrate reduction to ammonium (DNRA). While denitrification is a major source of the greenhouse gas nitrous oxide, DNRA retains mineral N in the ecosystem in the form of ammonium. The aim of this study is to investigate the competition of these two processes in order to better understand the fate of nitrate in agricultural soil.

## Method

To compare the importance of denitrification and DNRA, we conducted a ¹⁵N labelling experiment with two agricultural soils: an annual crop rotation with cereals and a grassland rotation system ('ley') with perennial forage crops and barley from a long-term trial field site near Uppsala (Sweden), both with different fertilisation levels. In laboratory incubations with fresh soil, subsamples of each treatment were enriched with ¹⁵N labelled ammonium, nitrate or both moieties at about 25% of the native concentrations. For multiple time steps after labelling, we will analyse ¹⁵N enrichment of mineral N species from soil extractions, and of nitrous oxide from headspace gas samples. The gross rates of denitrification and DNRA will be quantified using the *Ntrace* model [2]. Furthermore, we analysed soil properties and quantified the 16S gene of soil bacteria, the ITS gene of fungi, the NirS+NirK- and NosZI+NosZII genes of denitrifying bacteria, and the NrfA gene of DNRA performing bacteria using the qPCR in order to better understand what microorganisms are involved and what conditions favour either process.

## Results

Preliminary results indicate that increased denitrification produced larger amounts of nitrous oxide in the crop soil, whereas more mineral N was conserved in the ley soil. In addition, analysis of the marker genes showed higher abundance of bacteria capable of denitrification than DNRA in the fertilised treatments indicating higher genetic potential for nitrous oxide emissions. These data agree with previous findings that N limited ecosystems, here represented by lower fertilisation levels and higher $C:NO_3^-$ ratios, conserve and re-cycle mineral nitrogen through DNRA [3, 4].

## Conclusions

Our results suggest that different long-term agricultural management practices shift the importance of denitrification and DNRA due to altered soil conditions. However, it is still uncertain if and when DNRA can be an important N recycling mechanism in agricultural soil. For this, further work will be carried out for quantification of the gross N transformation rates and to evaluate the environmental factors that control both processes and the involved microbial communities.

## References

[1] Sutton, M.A., Howard, C.M., Erisman, J.W., Billen, G., Bleeker, A., Grennfelt, P., van Grinsven, H. & Grizzetti, B. 2011. The European Nitrogen Assessment. Cambridge University Press.

[2] Müller, C., Laughlin, R.J., Spott, O. & Rütting, T. 2014. Soil Biology and Biochemistry 72, 44-54.
[3] Rütting, T., Boeckx, P., Müller, C. & Klemedtsson, L. 2011. Biogeosciences 8, 1779-1791.

[4] Fernandes, S.O., Bonin, P.C., Michotey, V.D., Garcia, N. & LokaBharathi, P.A. 2012. Scientific Reports 2, 419.
# DENITRIFICATION OF GROUNDWATER INDUCED BY TWO CARBON SOURCES: VEGETAL COMPOST AND CRUSHED PALM TREE LEAVES

Alba Grau-Martínez¹, Raúl Carrey¹, Clara Torrentó¹,², Albert Folch³, Giorgio Ghiglieri⁴, Albert Soler¹, Neus Otero¹

¹Grup de Mineralogia Aplicada i Geoquímica de Fluids, Departament de Cristal·lografià, Mineralogia i Dipòsits Minerals, SIMGEO UB-CISC, Facultat de Geologia, Universitat de Barcelona (UB), C/Martí i Franquès, s/n - 08028 Barcelona, Spain, ²Centre for Hydrogeology and Geothermics, University of Neuchâtel, 2 Rue Emile-Argand 11,2000 Neuchâtel, Switzerland, ³Grup d'Hidrologia Subterrània, Departament d'Enginyeria del Terreny, Cartogràfica i Geofisica, Universitat Politècnica de Catalunya-Barcelona Tech, Jordi Girona, 1-3, 08034 Barcelona, Spain, ⁴Department of Chemical and Geological Science, University of Cagliari, Via Trentino 51, 09127 Cagliari, Italy

## Objectives

Artificial aquifer recharge with infiltration ponds is becoming a common method for enhancing groundwater supply and potentially improving water quality during infiltration [1]. Additionally, in infiltration ponds a reactive layer can be installed to create favourable conditions to induce biodegradation of target contaminant/s. Denitrification is an example of a process that could be achieved through artificial recharge with a reactive layer.

In the present study, the efficiency of two carbon sources as potential reactive layers was evaluated. The carbon sources were commercial vegetal compost, and palm tree leaves. The compost was studied because it is already used at the bottom of an infiltration pond in an artificial recharge system in Catalonia [2]. The palm tree leaves were tested in order to be used as reactive layer in an artificial recharge system planned in the Maghreb Region. We examined the efficacy of the two materials by means of flow-through experiments.

## Method

Commercial compost was obtained from a composting plant located in Moià (Catalonia) and palm tree leaves were from Maghreb region. Two flow-through experiments were carried out using glass cylindrical columns (35 cm high, 9 cm inner diameter), one filled with commercial compost and the other filled with crushed palm tree leaves. In both cases, the studied material was homogeneously mixed with clean silica sand (Panreac®) to increase permeability. The experiments were set up and carried out in an anaerobic chamber with an Ar atmosphere to avoid the presence of O₂. The input water used was water with a composition very similar to the Llobregat River and it was spiked with nitrate at different concentration levels (see below). The flow rate in the column experiments was controlled by a peristaltic pump (Micropump Reglo Digital 4 channels ISMATEC). Eh, pH and conductivity were measured daily at the outflow water. Samples were collected for hydrochemical analysis (major and minor cations, anions, dissolved inorganic carbon (DIC), non-purgeable organic carbon (NPOC)) and isotopic analyses (δ¹⁵N and δ¹⁸O of dissolved nitrate, δ¹⁵N of ammonium, δ³⁴S and δ¹⁸O of dissolved sulphate, δ¹³C of dissolved inorganic carbon).

## Results

In both flow-through experiments complete nitrate removal was observed. In the commercial compost experiment complete nitrate removal was achieved after 10 days using an inflow nitrate content of 0.81 mM. An initial increase in nitrate concentration up to 4.84 mM was observed due to N leaching from the compost. In the palm tree experiment complete nitrate removal was achieved after 4 days using 1.61 mM NO₃⁻ as inflow concentration. In this case an initial release of 4.9 mM NH₄⁺ was observed. Nitrite accumulation, produced if the denitrification reaction is not complete, was detected in both experiments with concentration up to 1.32 mM in the compost experiment and 0.06 nM in the palm tree experiment. In both experiments, nitrite concentration diminished to values close to 0.1mM after few days.

The isotopic enrichment factors for N (εN) and O (εO) in the flow-through experiments were calculated
from the slope of the regression lines that fit the data of the natural logarithm of nitrate concentration vs. δ¹⁵N and δ¹⁸O-NO₃⁻, respectively. The values of εN and εO for vegetal compost and crushed palm tree were -13.3‰ and -11.0‰, and -11.1‰ and -10.7‰, respectively. The εN/εO ratios were found to be 1.2 for vegetal compost and 1.04 for palm tree-mediated denitrification, which are within the typical range for denitrification [3].

## Conclusions

Flow-through experiments are a useful method to assess the role of different electron donors that can promote denitrification, to quantify the attenuation rates and to obtain isotope enrichment factors. The present work evaluated two different carbon sources for inducing denitrification during artificial recharge activities by means of flow-through experiments. The experiments demonstrate that (1) the commercial compost enhanced nitrate reduction although an initial release of nitrite was observed; (2) palm tree leaves were a good carbon source to induce denitrification although further studies should be performed in order to minimize nitrite and ammonium production.

## Acknowledgments

This work has been financed by the projects: REMEDIATION from the Spanish Government (CGL2014-57215-C4-1-R), MAG from the Catalan Government (2014SGR-1456), WADIS-MAR, (Water harvesting and Agricultural techniques in Dry lands: an Integrated and Sustainable model in Maghreb Regions -ENPI/2011/280-008) from the European Commission and MARSOL (Demonstrating Managed Aquifer Recharge as a Solution to Water Scarcity and Drought) from the European Union Seventh Framework Programme (FP7/2007-2013, under grant agreement n° 619120).

## References

[1] Dillon, P. 2005. Future management of aquifer recharge. Hydrogeology Journal 13, 313-316.

[2] Valhondo, C., Carrera, J., Ayora, C., Tubau, I., Martinez-Landa, L., Nödler, K., Licha, T. 2015. Characterizing redox conditions and monitoring attenuation of selected pharmaceuticals during artificial recharge through a reactive layer. Science of the Total Environment 512-513, 240-250.

[3] Torrentó, C., Cama, J., Urmeneta, J., Otero, N., Soler, A. 2010. Denitrification of groundwater with pyrite and *Thiobacillus denitrificans*. Chemical Geology 278, 80-91