bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrate leaching following autumn and winter application of animal manures to grassland
Authors: Smith K.A. , Beckwith C.P. , Chalmers A.G. , Jackson D.R.
Published: August 2010

Abstract. Under a UK Government consultation procedure announced in 2001, it was proposed that measures agreed within already designated Nitrate Vulnerable Zones (NVZ ‘s) would be extended to include a considerably increased area of England, Wales and Scotland. Since existing NVZ ‘s in the UK have included relatively little grassland, it is important to examine how nitrate losses from grassland areas, especially from animal manures, one of the major potential sources of nitrate loss, can be minimized. Experiments were carried out on freely draining grassland soils at four sites (Devon, Hampshire, Shropshire and N Yorkshire) representative of a wide range of climatic and farming conditions across lowland England, over a four year period, 1990/91 to 1993/94. Slurry was applied to experimental plots over a range of times (including June and then monthly, from September to January) at a target rate of 200 kg N ha–1. Nitrogen leaching over the four years ranged from 0 to >50% of applied slurry N, with the largest losses occurring following applications in the September to November period. The use of a nitrification inhibitor with slurry applied in November failed to provide consistent reduction in nitrate leaching.

A strategy to reduce the risk of N leaching from manures applied to freely draining grassland soils must take account of the characteristics of the manure, in particular its N content, the application rate and the amount of excess rainfall following application. The experimental results suggest that slurry applications to freely draining grassland, in September, October and November should generally be avoided, the rationale for this being dependent on the amount of excess rainfall subsequent to application. Farmyard manure represents a lower risk and does not justify the restrictions on application timing that appear to be necessary with slurry.
A comparative study of the microbiology of soils managed under organic and conventional regimes
Authors: Shannon D. , Sen A.M. , Johnson D.B.
Published: August 2010

Abstract. Previous studies of the microbial status of soils managed under ‘organic’ and ‘conventional’ regimes have produced conflicting evidence of whether there are distinct differences in the size, composition and activity of the soil microbial biomass which may be attributed to management practice. In the present study, we have compared the microbiology of organically‐ and conventionally‐managed soils at (primarily) two farms in England, over a two year period. Differences in microbial communities in soils under different management practice were subtle rather than dramatic. Many of the parameters measured, including total C and microbial biomass C, often showed no consistently significant differences in soils under different management. In soils from one farm, concentrations of ATP in Ringers solution soil extracts were mostly found to be significantly greater in organically‐managed than in comparable conventionally‐managed soils. While indirect (plate) counts showed that there were similar numbers of cultivable microorganisms present in these soils, total counts of bacteria (via DAPI‐staining) were found to parallel the trends found for readily‐extractable ATP. Numbers of metabolically‐active bacteria, determined by FISH analysis using a EUB338 probe to detect ribosome‐rich cells, indicated that the percentage of metabolically‐active bacteria present was not determined by management practice. Total and active fungi were also found to be more abundant in organically‐managed soils. It was concluded that changes in soil microbiology may occur as a consequence of switching to organic land management, but these may not be detectable by methods used frequently to assess soil biomass. In particular, increased numbers of viable but non‐culturable bacteria and fungi in organically‐managed soils points to a greater physiological diversity of microorganisms in such situations.
Potassium budgets in grassland systems as affected by nitrogen and drainage
Authors: Alfaro M.A. , Jarvis S.C. , Gregory P.J.
Published: August 2010

Abstract. The main inputs, outputs and transfers of potassium (K) in soils and swards under typical south west England conditions were determined during 1999/00 and 2000/01 to establish soil and field gate K budgets under different fertilizer nitrogen (N) (0 and 280 kg ha−1 yr−1) and drainage (undrained and drained) treatments. Plots receiving fertilizer N also received farmyard manure (FYM). Potassium soil budgets ranged, on average for the two years, from −5 (+N, drained) to +9 (no N and undrained) kg K ha−1 yr−1 and field gate budgets from +23 (+N, drained) to +89 (+N, undrained). The main inputs and outputs to the soil K budgets were fertilizer application (65%) and plant uptake (93%). Animals had a minor effect on K export but a major impact on K recycling. Nitrogen fertilizer application and drainage increased K uptake by the grass and, with it, the efficiency of K used. It also depleted easily available soil K, which could be associated with smaller K losses by leaching.
Nitrous oxide emissions from artificial urine patches applied to different N‐fertilized swards and estimated annual N2O emissions for differently fertilized pastures in an upland location in Germany
Authors: Anger M. , Hoffmann C. , Kühbauch W.
Published: August 2010

Abstract. Artificial urine containing 20.2 g N per patch of 0.2 m2 was applied in May and September to permanent grassland swards of a long‐term experiment in the western uplands of Germany (location Rengen/Eifel), which were fertilized with 0, 120, 240, 360 kg N ha−1 yr−1 given as calcium ammonium nitrate. The effect on N2O fluxes measured regularly during a 357‐day period with the closed‐chamber technique were as follows. (1) N2O emission varied widely among the fertilized control areas without urine, and when a threshold water‐filled pore space >60% was exceeded, the greater the topsoil nitrate content the greater the flux from the individual urine patches on the fertilized swards. (2) After urine application in May, 1.4–4.2% of the applied urine‐N was lost as N2O from the fertilized swards; and after urine application in September, 0.3–0.9% of the applied urine‐N was lost. The primary influence on N2O flux from urine patches was the date of simulated grazing, N‐fertilization rate being a secondary influence. (3) The large differences in N2O emissions between unfertilized and fertilized swards after May‐applied urine contrasted with only small differences after urine applied in September, indicating an interaction between time of urine application and N‐fertilizer rate. (4) The estimated annual N2O emissions were in the range 0.6–1.6 kg N2O‐N per livestock unit, or 1.4, 3.6, 4.1 and 5.1 kg N2O‐N ha−1 from the 0–360 kg ha−1 of fertilizer‐N. The study demonstrated that date of grazing and N‐fertilizer application could influence the N2O emission from urine patches to such an extent that both factors should be considered in detailed large‐scale estimations of N2O fluxes from grazed grassland.
Evaluating the impact of soil management on soil loss in olive orchards
Authors: Gómez J.A. , Battany M. , Renschler C.S. , Fereres E.
Published: August 2010

Abstract. The effects of soil management on soil losses from olive plantations in southern Spain were evaluated using the Revised Universal Soil Loss Equation (RUSLE), a review of published experiments, and preliminary results of an on‐going field trial. Experimental data were used to parameterize the RUSLE for olive orchards under various soil management regimes. The predictions agreed qualitatively with the data available, and the model provided a simple way to assess the effects of soil management on erosion. Our results showed that no‐tillage caused the greatest soil loss, while cover crops showed the least. Tillage and planting following contours proved only partially effective and did not reduce soil erosion as much as protective crops. One scenario studied suggests that, on slight to moderate slopes, land transformed from row crops to olive orchards may remain below the maximum tolerable soil erosion limit, if a cover crop is included between the trees. A scenario for marginal olive orchards located on steep slopes suggests that effective erosion control could only be achieved with a cover crop system that would have the side‐effect of reducing the yield of rain‐fed olives. Quantifying the effects of soil management on soil erosion in olive orchards is uncertain because very few experimental results are available. Further research that monitors soil loss in carefully selected long‐term experiments at different scales and follows the changes in key soil parameters is urgently required to develop effective erosion control policies.
Effects of solid olive‐mill waste addition to soil on sorption, degradation and leaching of the herbicide simazine
Authors: Albarrán A. , Celis R. , Hermosín M.C. , López‐Piñeiro A. , Ortega‐Calvo J.J. , Cornejo J.
Published: August 2010

Abstract. A laboratory study was conducted to investigate the effects of adding an intermediary byproduct of olive oil extraction (alperujo or solid olive‐mill waste, SOMW) on the sorption, degradation and leaching of the herbicide simazine in a sandy loam soil. The effect of SOMW addition on soil porosity was also assessed. The soil was amended in the laboratory with SOMW at two different rates (5% and 10% w/w). Simazine sorption isotherms showed a great increase in herbicide sorption after SOMW addition to soil; sorption increased with the amount of SOMW added. Incubation studies showed extended persistence by reduced biodegradation of simazine in the soil amended with SOMW compared with the unamended soil. Although the addition of SOMW to soil increased the total porosity, breakthrough curves of simazine in handpacked soil columns showed that SOMW addition retarded the vertical movement of the herbicide through the soil and reduced the total amount of herbicide leached. It appeared that the longer residence time of simazine in the amended soil columns (>20 days) compared with that in the unamended soil column (<20 days) allowed enhanced degradation and/or irreversible sorption under column leaching conditions. The results revealed important changes in herbicide behaviour upon SOMW addition, confirming the need to assess these changes in order to optimize the combined use of organic wastes and soil‐applied pesticides.
Estimates of carbon stock changes in Belgian cropland
Authors: Sleutel S. , De Neve S. , Hofman G.
Published: August 2010

Abstract. Article 3.4 of the Kyoto Protocol allows carbon emissions to be offset by demonstrable removal of carbon from the atmosphere by improved management of agricultural soils. To make use of this possibility, a good estimate of soil organic carbon (SOC) stocks and baseline emissions (in 1990) are crucial factors. Over 210 000 topsoil (0–24 cm) measurements have been made in Belgian cropland in the period 1989–1999, which are available for seven different agro‐pedological regions and for three periods (1989–91, 1992–95, 1996–99). We used this extensive SOC data set to estimate SOC stocks and fluxes in Belgian cropland. The measurements of SOC were extrapolated to 1 m depth using an exponential SOC depth distribution model, based on another large data set of over 5184 fully described soil profiles on Belgian cropland made during the National Soil Survey. The SOC data were combined with cropland area figures to calculate SOC stocks to 1 m depth. The 1990 baseline SOC flux of Belgian cropland was then obtained using two different calculation methods, which each yielded similar results and showed that SOC stocks were decreasing in the 1990s at a mean rate of 608 kton OC yr−1. Consequently, a large part of the Belgian cropland acted as a net source of CO2 emissions during the period 1989–1999.
Field studies of the effects of jute geotextiles on runoff and erosion in Shropshire, UK
Authors: Mitchell D.J. , Barton A.P. , Fullen M.A. , Hocking T.J. , Zhi Wu Bo , Yi Zheng
Published: August 2010

Abstract. Jute geotextiles are widely used to stabilize steep banks and road cuttings. Jute protects bare surfaces until seeded grass becomes established, then after several years, the jute decays. To evaluate two types of jute geotextiles, eight erosion plots were established in July 1994 at the Hilton Experimental Site, Shropshire, UK. On 10 April 1995, the plots were treated as follows:

jute geotextile net;

jute mat;

perennial rye grass (Lolium perenne); and

bare soil, with duplicates of each treatment.

Over one year, sediment yields from jute net and jute mat were 1.1% and 1.2%, respectively, of the yield from the bare control. Although both had similar soil protection qualities, runoff was very different. The runoff from the jute net was 35% and the jute mat 247% of the control. Results demonstrate the effectiveness of jute net for erosion and runoff control, while the jute mat may both conserve soil and ‘harvest’ rain or redirect runoff.
Improvements in soil quality and performance of mycorrhizalCistus albidusL. seedlings resulting from addition of microbially treated sugar beet residue to a degraded semiarid Mediterranean soil
Authors: Alguacil M.M. , Caravaca F. , Azcón R. , Pera J. , Díaz G. , Roldán A.
Published: August 2010

Abstract.A field experiment was undertaken to assess the effectiveness of a combined treatment, involving addition ofAspergillus niger‐treated sugar beet (SB) residue in the presence of rock phosphate and mycorrhizal inoculation of seedlings withPisolithus tinctorius. The aim was to improve the physical, chemical, biochemical and biological properties of a degraded semiarid Mediterranean soil. Short‐term effects of such improvements on the establishment ofCistus albidusL. seedlings were evaluated. Eight months after planting, macronutrients (NPK), total carbohydrates, water‐soluble C, water‐soluble carbohydrates, microbial biomass C and enzyme activities (dehydrogenase, urease, protease, acid phosphatase and β‐glucosidase) measured in the rhizosphere soil ofC. albiduswere increased greatly by addition of fermented SB residue. Soil structural stability improved only with the fermented SB addition (about 79% higher in the amended soils than in the non‐amended soils). The mycorrhizal inoculation was the most effective treatment in improving the growth ofC. albidusplants, but only slightly improved soil quality. Growth of inoculated plants was about 33% greater than plants grown in the amended soil and about 131% greater than control plants. The combined benefit of mycorrhizal inoculation of seedlings and addition of fermented SB residue to soil on plant growth was similar to that of the treatments applied individually.
Soil erosion potential of organic versus conventional farming evaluated by USLE modelling of cropping statistics for agricultural districts in Bavaria
Authors: Auerswald K. , Kainz M. , Fiener P.
Published: August 2010

Abstract.Organic agriculture (OA) aims to identify a production regime that causes less environmental problems than conventional agriculture (CA). We examined whether the two systems differ in their susceptibility to soil erosion by water. To account for the large heterogeneity within the rotations practised on different farms, we chose a statistical evaluation which modelled erosion using the USLE method from the cropping statistics for 2056 districts in Bavaria (70 547 km2; 29.8% arable). Physical conditions of erosion were determined in a rectangular grid yielding 13 125 grid‐cells of c. 5 km2each. For validation, erosion was measured in 10 sub‐watersheds on two neighbouring OA and CA farms over 8 years (287 erosive events). On average, about 15% less erosion on arable land was predicted for OA than for CA due to the larger area of leys, although OA occupies areas that are susceptible to erosion more often than CA. The same conclusions could be drawn from the validation data. These data also demonstrated that erosion could be reduced considerably below 1 t ha−1yr−1with best management practices under both farming systems. In contrast, at the countrywide scale, cropping did not change adequately with site conditions favouring erosion. The need for erosion control seems not to influence crop rotation decisions on erosion‐prone sites.
Field hydraulic properties of an Alfisol under various fallow systems in southwestern Nigeria
Authors: Salako F.K. , Kirchhof G.
Published: August 2010

Abstract. The effects of various fallow management systems and cropping intensities on water infiltration were measured on an Alfisol at Ibadan in southwestern Nigeria. The objective was to determine the influence of the land use systems (a combination of crop–fallow sequences and intercropping types) on soil hydraulic properties obtained by disc permeameter and double‐ring infiltration measurements. The experiment was established in 1989 as a split‐plot design with four replications. The main plots were natural fallow, planted Pueraria phaseoloides and planted Leucaena leucocephala. The subplots were 1 year of maize/cassava intercrop followed by 3‐year fallow (25% cropping intensity), or 2‐year fallow (33% cropping intensity), or 1‐year fallow (50% cropping intensity), or no fallow period (100% cropping intensity). Water infiltration rates and sorptivities were measured under saturated and unsaturated flow. Irrespective of land use, infiltration rates at the soil surface (121–324 cm h−1) were greater than those measured at 30 cm depth (55–144 cm h−1). This indicated that fewer large pores were present below 30 cm depth compared with 0–30 cm depth. Despite some temporal variation, sorptivities with the highest mean value of 93.5 cm h−½ increased as the cropping intensity decreased, suggesting a more continuous macropore system under less intensive land use systems. This was most likely due to continuous biopores created by perennial vegetation under long fallow systems. Intercropped maize and cassava yields also increased as cropping intensity decreased. The weak relationship between crop yields and hydraulic conductivity/infiltration rates suggests that the rates were not limiting.
Quantification of the effects of soil compaction on water flow using dye tracers and image analysis
Authors: Mooney S.J. , Nipattasuk W.
Published: August 2010

Abstract. Soil compaction has long been considered to be a problem in arable land, primarily because it causes damage to soil structure, which can lead to serious reduction in crop yields. However, few studies have sought to investigate the effects of soil compaction on the water transport regime of modified soil pore systems. We attempted to quantify the effects of soil compaction on the initiation of preferential flow by using dye tracers and image analysis. A laboratory methodology involving rainfall simulation enabled us to quantitatively evaluate differences in the mechanisms of water flow between two soil types at several degrees of compaction. The results suggested significant differences in the types of water flow pathways between clay loams and sandy loams at different extents of compaction. In the sandy loam, it was concluded that a high degree of compaction led to an increased likelihood of preferential flow, whereas a more uniform movement of soil water occurred at less compaction. By contrast, preferential routing of soil water was recorded in the clay loam, except at the highest measured compaction. The results indicate that the visual techniques of dye tracing and image analysis could enable improved understanding of flow pathways of soil water associated with soil compaction.
Modelling crop production potentials for yield gap analysis under semiarid conditions in Guquka, South Africa
Authors: Verdoodt A. , Van Ranst E. , Van Averbeke W.
Published: August 2010

Abstract. Hierarchical crop growth models can contribute significantly to land quality research because the yield gap between the estimated optimum and the actual crop production has been identified as a major land quality indicator. This study describes a three‐level, hierarchical crop production model, simulating radiation‐thermal, water‐limited and natural production potentials of annual crops. Input requirements have been kept low to ensure its applicability to developing regions, which often have access only to limited data. The simplicity of this model also has disadvantages: inconsistencies have been reported when applying this model in semiarid regions, which are characterized by very irregular rainfall patterns. Revision of the water balance, which simulates the availability of water, was required. The modified model was validated using the experimental yields of maize and sunflower in Guquka, a semiarid region of South Africa. Yields were estimated very well, possible improvements to crop production were identified and implications for land‐use planning highlighted. Yield gap analysis revealed that radiation, sunshine and temperature are favourable for crop production, but the heavy dependence on rainfall makes the region very vulnerable to drought, with devastating impact on yields. The generally low chemical soil fertility further reduces crop performance.
Effects of the nitrification inhibitor dicyandiamide on potassium, magnesium and calcium leaching in grazed grassland
Authors: Di H.J. , Cameron K.C.
Published: August 2010

Abstract. Leaching of calcium (Ca), potassium (K) and magnesium (Mg) from urine patches in grazed grassland represents a significant loss of valuable nutrients. We studied the effect on cation loss of treating the soil with a nitrification inhibitor, dicyandiamide (DCD), which was used to reduce nitrate loss by leaching. The soil was a free‐draining Lismore stony silt loam (Udic Haplustept loamy skeletal) and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The treatment of the soil with DCD reduced Ca2+ leaching by the equivalent of 50%, from 213 to 107 kg Ca ha−1 yr−1 on a field scale. Potassium leaching was reduced by 65%, from 48 to 17 kg K ha−1 yr−1. Magnesium leaching was reduced by 52%, from 17 to 8 kg Mg ha−1 yr−1. We postulate that the reduced leaching loss of these cations was due to the decreased leaching loss of nitrate under the urine patches, and follows from their reduced requirement as counter ions in the drainage water. The treatment of grazed grassland with DCD thus not only decreases nitrate leaching and nitrous oxide emissions as reported previously, but also decreases the leaching loss of cation nutrients such as Ca2+, K+ and Mg2+.
Effects of intensive monocropping of bananas on properties of volcanic soils in the uplands of the French West Indies
Authors: Clermont‐Dauphin C. , Cabidoche Y.‐M. , Meynard J.‐M.
Published: August 2010

Abstract. On the volcanic soils of the uplands of the French West Indies, banana monocropping has been practised since about 1980, mostly with large inputs of chemicals and replanting every three to five years after ploughing. However, in Guadeloupe less intensive cropping systems with only few added chemicals are still being used. The effects of the intensive practices on the physical, chemical and biological attributes of soils were evaluated on 34 farmed fields, which were selected to include the diverse soils and management practices found in the uplands of South Basse‐Terre. Management was classified into four groups to differentiate effects of fertilizers, nematicides and tillage over at least 10 years. The population of the parasitic nematode Radopholus similis was, on average, greater 3 months after the application of nematicides. Thus, the use of nematicides increases the dependency of yield on nematicides. Ploughing decreased soil organic matter in the 0–10 cm layer as well as microbial respiration and earthworm biomass, but increased banana root infestation by R. similis. Ploughing was also associated with a change in soil structure, as revealed by the decrease in soil water content at −1 kPa potential and the increased infiltration rate of water into the 0–10 cm layer. The use of fertilizers has advantages for the maintenance or increase of soil reserves of K. However, due to the decreasing of negative electrical charges in the lower layers of andosols, where pH remains low, the majority of the cations supplied by fertilizers, mainly potassium, are prone to leaching.
Organic chlorine and chloride in submerged paddy soil: a case study in Anhui province, southeast China
Authors: Johansson E. , Xin Zhang Björn , Zhengyi Hu , Sandén P. , Öberg G.
Published: August 2010

Abstract.Efforts to understand the fate of organochlorine compounds in arable soil have concentrated on anthropogenic compounds, in spite of the fact that organochlorine compounds are both produced and mineralized in soil through natural processes. In order to understand the fate of chlorinated pesticides, it is necessary to take account of the natural chlorine cycle. The present study is a first attempt to illuminate the relationship between the natural chlorine cycle and agricultural practices. The concentration and storage of organic chlorine (Clorg) and chloride (Clinorg) were determined in topsoil of a paddy field compared to an adjacent afforested hill at a sampling site in the Meicun area, Anhui Province, China. The concentration of Clorg, as well as the chlorine‐to‐carbon ratio, was significantly lower in the paddy field samples than in the forest soil samples. A weak relationship between the concentration of Clorgand the organic carbon content was observed in the paddy field, in contrast to the observations made in the adjacent forest soil as well as those made in previous studies, which have suggested a positive correlation between organic carbon content and Clorg. The similarity between our results at the forest site and the previous studies, which have been carried out in temperate regions, suggests that it is the land use rather than the climate that makes the current paddy soil results different. Our results suggest that the contribution of Clorgto the paddy soil from above‐ground litter and from production within the soil are small or negligible compared with the contribution from pesticide application and wet and dry deposition.
Simulating transport of E. coli derived from faeces of grazing livestock using the macro model
Authors: McGechan M.B. , Vinten A.J.A.
Published: August 2010

Abstract. Coliforms such as Escherichia coli and E. coli O157 are present in faeces deposited on the ground by grazing livestock, which gives rise to environmental concerns about the consequences of their transport in soil water draining to rivers, lakes, groundwater, water supplies and bathing waters. Following a similar study in relation to slurry spreading (Soil Use and Management 2003; 19, 321–330), a two‐stage approach was adopted to using the dual‐porosity contaminant transport model macroto simulate processes by which E. coli microorganisms from grazing livestock (sheep) pass through the soil to receiving waters via field drains. First, model parameter values were selected to reproduce experimental measurements showing rapid flows of the organisms by macropore flow without trapping in smaller pores. However, because of the large number of parameters and likely experimental errors, the set of values chosen, although plausible, is not necessarily unique and so any predictions should be considered provisional pending validation. Second, a series of predictive simulations was carried out to test the influence of soil and weather conditions on losses to field drains during grazing. These showed that E. coli losses were influenced almost entirely by the soil water content at the time of grazing, rising to a high level during grazing in wet conditions, but low or zero under dry conditions. In contrast, rainfall at the time of grazing had almost no consistent effect, other than large losses on the occasional days with over 20 mm of rain. Overall losses for a period of grazing were generally small during summer, but rose to a high level if grazing continued into autumn, due to the increase in soil water content. This demonstrates that there would probably be substantial reductions in the environmental risks of water pollution by E. coli and other faecal microorganisms if continuous grazing were stopped around early September and replaced by grazing on dry days only.
Water‐stable aggregates and organic matter pools in a calcareous vineyard soil under four soil‐surface management systems
Authors: Goulet E. , Dousset S. , Chaussod R. , Bartoli F. , Doledec A.F. , Andreux F.
Published: August 2010

Abstract. Vineyards in Champagne, France are generally situated on slopes where the soils are subject to erosion. Therefore it is important to find a soil‐surface management practice that protects the soil against water erosion. We assessed the potential of mulches or grass covers to stabilize soil aggregates in a calcareous sandy loam from a vineyard in Champagne after 9 years under different management systems. Four different treatments were studied: (i) a bluegrass (Poa pratensis) surface cover between the vine rows (GC) with bare soil under the vines (R); two organic mulches of (ii) coniferous (CB) or (iii) poplar (PB) bark that covered the entire soil surface, and (iv) bare soil between the rows as a control. The bark amendments were applied every 3 years at rates of 61 and 67 t ha−1 for the PB and CB treatments, respectively. The kinetics of soil disaggregation in water fitted a power law (A=K t−D), in which K was the fraction of water‐stable >200 μm aggregates remaining after 1 hour of wet‐sieving. In the 0–5 cm layer, aggregate stability was greater for GC (K=21.7), CB (K=15.2) and PB (K=13.6) than for the control (K=10.5) and R (K=11.8). In the 0–20 cm layer, CB also stabilized soil aggregates (K=14.0–15.0); but PB did not. Structural stability was more strongly related to total organic carbon (R2=0.64, P <0.001) than to microbial biomass carbon (R2=0.54, P<0.001). A bluegrass cover enhanced structural stability in the 0–5 cm and 0–20 cm layers (K=14.2), probably because of intense root development and rhizodeposition enhancing microbially produced metabolites, such as carbohydrates. Establishing grass cover or applying bark mulch are effective agricultural practices that improve soil aggregate stability and thus should reduce soil erosion. The vegetative growth of the vines was greater on the soils amended with bark mulches and less on the grass covered soils compared with the control soil; however, no difference in wine quality was observed among the different treatments.
Soil carbon stocks and projected changes according to land use and management: a case study for Kenya
Authors: Batjes N.H.
Published: August 2010

Abstract. Soil organic (SOC) and inorganic carbon (SIC) stocks of Kenya were determined using four different methods to provide baseline data. The assessments used an updated version of the 1:1 M soil and terrain database for the country. Estimates for national SOC stocks to 1 m depth ranged from 3452 to 3797 Tg C. The findings highlight the need for comprehensive databases of soil and terrain data of good quality that consider more than one representative profile per soil component. The 95% confidence limits for the median, area‐weighted SOC content were largest in the humid highlands (15.4–15.7 kg C m−2) and smallest in the hot arid zone (4.4–4.5 kg C m−2). Conversely, for SIC these values were largest in the arid zone (4.3–4.5 kg C m−2) and smallest in high rainfall areas (<0.1 kg C m−2). Many croplands in Kenya have been over‐exploited, resulting in nutrient depletion and loss of organic matter. The SOC gains considered ecologically and technically feasible upon improved management of croplands were estimated at 5.8–9.7 Tg C over the next 25 years. This corresponds to an estimated annual mitigation potential of 5–9% of Kenya's CO2‐C emissions from fossil fuels, cement manufacturing and land use change for 1990.
Dry farming with soils under natural tephra cover in Lanzarote, Spain
Authors: Tejedor M. , Jiménez C. , Díaz F.
Published: August 2010

Abstract. The volcanic island of Lanzarote (Canary Islands, Spain) is one of the most arid parts of the European Union. During the eruptions of 1730–36, a third of the island was covered with lava and pyroclastic material. In areas under basaltic tephra, an agrosystem has been developed that allows a form of dry farming that has become a key component of the local economy. This article illustrates the effectiveness of the layer of natural tephra mulch in conserving soil and water.
Carbon sequestration and saving potential associated with changes to the management of agricultural soils in England
Authors: King J.A. , Bradley R.I. , Harrison R. , Carter A.D.
Published: August 2010

Abstract. The potential for soil organic carbon sequestration, energy savings and the reduction of the emission of greenhouse gases were investigated for a range of changes in the management of tilled land and managed grassland. These parameters were modelled on a regional basis, according to local soils and crop rotations in England, and avoided the use of soil related indices. The largest carbon sequestration and saving contribution possible comes from an increase in the proportion of permanent woodland, such that a 10% change in land use could amount to 9 Mt C yr−1 in the initial years (arable and grassland). Changes in arable management could make a significant contribution to an abatement strategy if carried out in concert with greater use of permanent conservation field margins, increased returns of crop residues and reduced tillage systems, contributing 1.3 Mt C yr−1 in the initial years. It should be noted, however, that true soil carbon sequestration would be only a minor component of this (125 kt C yr−1), the main part being savings on CO2 emissions from reduced energy use, and lower N2O emissions from reduced use of inorganic nitrogen fertilizer.
Yields of wheat and soil carbon and nitrogen contents following long‐term incorporation of barley straw and ryegrass catch crops
Authors: Thomsen I.K. , Christensen B.T.
Published: August 2010

Abstract. Three successive crops of winter wheat were grown on a sandy loam to test the residual effect of long‐term annual incorporation of spring barley straw at rates of 0, 4, 8 and 12 t ha−1, and ryegrass catch crops with or without additions of pig slurry. Soil receiving 4, 8 and 12 t ha−1 of straw annually for 18 years contained 12, 21 and 30% more carbon (C), respectively, than soil with straw removal, and soil C and nitrogen (N) contents increased linearly with straw rate. The soil retained 14% of the straw C and 37% of the straw N. Ryegrass catch‐cropping for 10 years also increased soil C and N concentrations, whereas the effect of pig slurry was insignificant. Grain yield in the first wheat crop showed an average dry matter (DM) increase of 0.7 t ha−1 after treatment with 8 and 12 t straw ha−1. In the two subsequent wheat crops, grain yield increased by 0.2–0.3 t DM ha−1 after 8 and 12 t straw ha−1. No grain yield increases were found after 4 t straw ha−1 in any of the three years. Previous ryegrass catch crops increased yields of wheat grain, but effects in the third wheat crop were significant only where ryegrass had been combined with pig slurry. Straw incorporation increased the N offtake in the first wheat crop. In the second crop, only 8 and 12 t straw ha−1 improved wheat N offtake, while the N offtake in the third wheat crop was unaffected. Ryegrass catch crops increased N offtake in the first and second wheat crop. Again, a positive effect in the third crop was seen only when ryegrass was combined with slurry. Long‐term, annual incorporation of straw and ryegrass catch crops provided a clear and relatively persistent increase in soil organic matter levels, whereas the positive effects on the yield of subsequent wheat crops were modest and transient.
Impact of pig slurry on soil properties, water salinization, nitrate leaching and crop yield in a four‐year experiment in Central Spain
Authors: Díez J.A. , Hernaiz P. , Muñoz M.J. , de la Torre A. , Vallejo A.
Published: August 2010

Abstract. The repeated application of pig slurry to agricultural soils may result in an accumulation of salts and a risk of aquifer pollution due to nitrate leaching and salinization. Under Mediterranean conditions, a field experiment on a sandy loam soil (Typic Xerofluvent) was performed with maize (Zea mays) in 1998, 1999 and 2001 to study the effects of applying optimal (P1) and excessive rates (P3) of pig slurry on soil salinization, nitrate leaching and groundwater pollution. The rate of pig slurry was established considering the optimal N rate for maize in this soil (170, 162 and 176 kg N ha−1 for 1998, 1999 and 2001, respectively). Pig slurry treatments were compared to an optimal N rate supplied as urea (U) and a control treatment without N fertilizer (P0). The composition of the slurries showed great variability between years. Mean NO3− leaching losses from 1998 to 2001 were 329, 215, 173 and 78 kg N ha−1 for P3, P1, U and P0 treatments, respectively. The amount of total dissolved salts (TDS) added to the soil in slurry application between 1998 and 2001 was 2019 kg TDS ha−1 for the P1 treatment and 6058 kg TDS ha−1 for the P3 treatment. As a consequence, the electrical conductivity (EC) of the slurry‐treated soils was greater than that of the control soil. The EC correlated significantly with the sodium concentration of the soil solution. Over the entire experimental period, 2653, 2202 and 2110 kg Na ha−1 entered the aquifer from the P3, P1 and P0 treatments, respectively. The P3 treatment did not significantly increase grain production in 1999 and 2001 compared with that achieved with the optimal N rate treatment (P1). This behaviour shows the importance of establishing application guidelines for pig slurry that will reduce the risk of soil and groundwater pollution.
Comparison of field techniques for sampling soil solution in an upland peatland
Authors: Reynolds B. , Stevens P.A. , Hughes S. , Brittain S.A.
Published: August 2010

Abstract. Results from recent studies of peatland biogeochemistry suggest that appropriate soil water sampling techniques are required in order to advance our understanding of peatland soil systems. In a comparative field experiment, concentrations of inorganic solutes and dissolved organic carbon (DOC) were measured in soil water extracted at a depth of 10 cm beneath the surface of deep peat by three techniques: zero‐tension (z‐t) lysimeters, PTFE suction samplers, and polysulfone suction samplers. The majority of solute concentrations were broadly similar, but mean concentrations of silicon, DOC, iron and aluminium in water extracted by z‐t lysimeters and PTFE samplers were in ratios of 1:5; 1:2; 1:5 and 1:3 respectively. Mean conductivity and concentrations of chloride and hydrogen ion were significantly larger in the z‐t lysimeter samples, which had sodium, potassium and magnesium to chloride ratios that were very similar to local rainfall. The z‐t lysimeters appeared to sample macropores preferentially, while the suction samplers collected micropore water.
Soil physical and hydraulic properties in a rice‐wheat cropping system in India: effects of rice‐straw management
Authors: Singh G. , Jalota S.K. , Sidhu B.S.
Published: August 2010

Abstract. The effects of rice‐straw management (incorporation, burning or removal) on soil organic carbon content and physical and hydraulic properties were determined after five years of rice–wheat cropping in a sandy loam soil in northwest India. Soil organic carbon content was greater with straw incorporation and straw burning than with straw removal, and aggregation status, total porosity, pore‐size distribution, bulk density, dispersion ratio and soil strength were correspondingly improved. The treatment effects were confined mainly to the 0–5 cm depth. Water retention was less with straw burning than straw removal, owing to increased water repellency of the soil surfaces. Cumulative infiltration and its rate after five hours were greater with straw incorporation than straw burning or removal. Air entry values were unaffected by straw management; however, the values were greater after rice harvest than after wheat harvest.
Long‐term effects of fallow, tillage and manure application on soil organic matter and nitrogen fractions and on sorghum yield under Sudano‐Sahelian conditions
Authors: Mando A. , Ouattara B. , Somado A.E. , Wopereis M.C.S. , Stroosnijder L. , Breman H.
Published: August 2010

Abstract.Soil organic matter (SOM) controls the physical, chemical and biological properties of soil and is a key factor in soil productivity. Data on SOM quantity and quality are therefore important for agricultural sustainability. In 1990, an experiment was set up at Saria, Burkina Faso on a sandy loam Lixisol to evaluate long‐term effects of tillage (hand hoeing or oxen ploughing) with or without 10 t ha−1yr−1of manure and fallowing on SOM and N concentrations and their distribution in particle size fractions. The field was sown annually to sorghum (Sorghum bicolor[L.] Moench). Ten years later, total organic C and total N, SOM fractions and their N concentrations, and sorghum yield were determined. Continuous sorghum cultivation without organic inputs caused significant losses of C and N in the hoed and ploughed plots. However, addition of manure to hoed plots was effective in maintaining similar levels of C and N to fallow plots. Without manure, SOM was mainly stored in the size‐fraction <0.053 mm (fine organic matter, FOM). SOM was mainly stored in the size‐fraction between 0.053 and 2 mm (particulate organic matter, POM). In plots with manure and in fallow plots, the addition of manure more than doubled POM concentrations, with levels in tilled plots exceeding those of the fallow plots, and the highest levels in manually hoed plots. Nitrogen associated with POM (POM‐N) followed a similar trend to POM. Hoeing and ploughing led to a decline in sorghum grain yield. Manure application increased yields by 56% in the hoed plots and 70% in the ploughed plots. Grain yield was not correlated with total SOM but was positively correlated with total POM. This study indicated that POM was greatly affected by long‐term soil management options.
Landscape‐scale soil quality change under different farming systems of a tropical farm in Hainan, China
Authors: Zhang H. , Zhang G.‐L.
Published: August 2010

Abstract. The impact of different tropical farming systems on soil quality was examined using a systematic sampling strategy. Total organic C, pH, extractable P, exchangeable K, bulk density, water stable aggregates, microbial biomass C, cation exchange capacity, soil depth, and clay content were determined. An assessment framework, including a minimum data set, linear scoring functions and weighted additive indices, was used to evaluate the soil quality of a tropical farm growing various crops in Hainan, China. Soil quality was evaluated according to four functions: water availability, nutrient availability, rooting suitability, and erosion resistance. Our results showed that soils were intrinsically lacking in nutrients and vulnerable to degradation, and that these problems were exacerbated by inappropriate management. There was strong evidence that long‐term rubber farming caused soil acidification, soil compaction, and depletion of organic matter and nutrients. By contrast, conservation practices in coffee plantations protected or improved organic matter concentration and soil structure, resulting in higher soil quality indices.
Critical aspects of potassium management in agricultural systems
Authors: Öborn I. , Andrist‐Rangel Y. , Askekaard M. , Grant C.A. , Watson C.A. , Edwards A.C.
Published: August 2010

Abstract. Fertilizer and manure application rate and timing are often based on the optimal nitrogen rate and not on potassium (K) requirements. This can lead to excess or shortage of K depending on the crop and rotation. In grass‐dominated agricultural production, including many organic farming systems, K has become a critical element, especially in areas dominated by coarse‐textured or organic soils. In this paper we review K management in relation to long‐term sustainability of both the soil resource and the production of crops of high yield and quality. One question for the future is whether we can adopt management options that favour efficient use of K and secure a sustainable future for global K reserves. For example, is it possible to enhance the release rate of K from soil mineral sources so that we require less fertilizer K from K‐bearing salt deposits? A reduction in external K inputs requires improved on‐farm recycling of K in order to reduce losses. We also need a better understanding of soil processes and soil–plant interactions and decision‐support tools to predict the potential K release from mineral weathering. Certain areas dominated by young, clay‐rich soils can potentially supply enough K, whereas other areas with coarse sandy or organic soils have a very low weathering potential and would thus need external inputs of K.
Nutrient management for intensive animal agriculture: policies and practices for sustainability
Authors: Sims J.T. , Bergström L. , Bowman B.T. , Oenema O.
Published: August 2010

Abstract. The intensity of animal production around the world has increased substantially during the last half‐century, which has led to large problems with the disposal of manures and waste waters. The focus of this paper is on the development of national policies to improve the nutrient management of concentrated animal feeding operations (CAFOs), where nutrients are invariably in surplus. To create proper nutrient management strategies for CAFOs, and to avoid environmental problems when surplus nutrients enter air, soil and water, we need to know the number of animals/birds in the unit, the quantity of manure/slurry produced, how this material is stored and handled and how much land is available for manure spreading. In this paper, we discuss the development of nutrient management strategies for CAFOs in Europe and North America, and the voluntary measures and environmental regulations related to this. For the planning of nutrient management to be comprehensive and efficient, we need expertise from several disciplines. This planning includes development of: animal diets that reduce the amounts of excreted nutrients; efficient storage and land application technologies; land application programmes to optimize yields and reduce nutrient losses; and strategies for use of excess manure outside the farm. Also, large‐scale efforts involving many stakeholders (farmers, governments and private industry) are needed to solve problems with nutrient imbalances over the long term. Efforts along these lines include manure relocation, alternative uses of manures, nutrient trading, and a general extensification of animal agriculture. The overall guiding principle for policies and planning should be a balance of nutrients, on farms as well as at larger scales.