bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport of trifluralin on wind-eroded sediment
Authors: Cessna A J , Larney F J , Kerr L A , Bullock M S
Published: April 2011

Wind erosion is one of the major forms of soil degradation on the Canadian prairies. Particulate matter emanating from agricultural soil can be transported long distances in the atmosphere and, if the soil has significant clay content, would contain particles less than 2 μm in diameter. Particles of this size range have been associated with respiratory health effects in humans and if they have pesticides associated with them the risk of health effects may be increased. A field experiment was conducted near Regina, Saskatchewan, to determine the trifluralin (2,6-dinitro-N,N-dipropyl-4-trifluoromethylaniline) content in wind-eroded sediment from a soil-incorporated application of the herbicide into Regina heavy (71%) clay soil. Three wind erosion events were monitored in which the total estimated soil loss was 62.4 Mg ha-1. The concentration of trifluralin in the winderoded sediment did not show a consistently significant increase with sampler height (10 to 100 cm) and, by implication, decreasing sediment particle size. The concentration of trifluralin in the wind-eroded sediment was lower than that in the incorporation layer and in the surface soil (upper 0.5 to 1 cm). The overall wind erosion loss of trifluralin, as a percent of the amount applied, during three erosion events was 1.4%. The results of this study indicate that human exposure to atmospheric particulate matter, especially in agricultural areas, may simultaneously involve exposure to pesticides. Key words: Trifluralin, wind erosion, wind-eroded sediment, heavy clay
Soil organic carbon stocks and flows in New Zealand: System development, measurement and modelling
Authors: Tate K. R. , Wilde R. H. , Giltrap D. J. , Baisden W. T. , Saggar S. , Trustrum N. A. , Scott N. A. , Barton J. P.
Published: April 2011

An IPCC-based Carbon Monitoring System (CMS) was developed to monitor soil organic C stocks and flows to assist New Zealand to achieve its CO2 emissions reduction target under the Kyoto Protocol. Geo-referenced soil C data from 1158 sites (0.3 m depth) were used to assign steady-state soil C stocks to various combinations of soil class, climate, and land use. Overall, CMS soil C stock estimates are consistent with detailed, stratified soil C measurements at specific sites and over larger regions. Soil C changes accompanying land-use changes were quantified using a national set of land-use effects (LUEs). These were derived using a General Linear Model to include the effects of numeric predictors (e.g., slope angle). Major uncertainties a rise from estimates of changes in the areas involved, the assumption that soil C is at steady state for all land-cover types, and lack of soil C data for some LUEs. Total national soil organic C stocks estimated using the LUEs for 0–0.1, 0.1–0.3, and 0.3–1 m depths were 1300 ± 20, 1590 ± 30, and 1750 ± 70 Tg, respectively. Most soil C is stored in grazing lands (1480 ± 60 Tg to 0.3 m depth), which appear to be at or near steady state; their conversion to exotic forests and shrubland contributed most to the predicted national soil C loss of 0.6 ± 0.2 Tg C yr-1 during 1990–2000. Predicted and measured soil C changes for the grazing-forestry conversion agreed closely. Other uncertainties in our current soil CMS include: spatially integrated annual changes in soil C for the major land-use changes, lack of soil C change estimates below 0.3 m, C losses from erosion, the contribution of agricultural management of organic soils, and a possible interaction between land use and our soil-climate classification. Our approach could be adapted for use by other countries with land-use-change issues that differ from those in the IPCC default methodology. Key words: Soil organic carbon, land-use change, stocks, flows, measurement, modelling, IPCC
Nitrogen release during decomposition of crop residues under conventional and zero tillage
Authors: Lupwayi N. Z. , Clayton G. W. , O’Donovan J. T. , Harker K. N. , Turkington T. K. , Soon Y. K.
Published: April 2011

The litter-bag method was used in field experiments to determine nitrogen (N) loss patterns from decomposing red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues under conventional and zero tillage. Nitrogen contained in crop residues ranged from 10 kg ha-1 in wheat under both tillage systems to 115 kg ha-1 in clover GM under zero tillage. The patterns of N loss (i.e., release), particularly from GM residues, over 52-wk periods varied with tillage, i.e., residues lost N more rapidly under conventional tillage than under zero tillage in the first 5 to 10 wk after residue placement. Net N immobilization was sometimes observed, particularly under zero tillage. Where net N release occurred, it ranged from 22% of wheat N under conventional tillage to 71% for clover N under conventional tillage; it was positively correlated with residue N concentration and microbial activity, and negatively correlated with C:N and lignin:N ratios in one study period. The amounts of N released were 2 kg ha-1 from wheat, 10 to 25 kg ha-1 from canola, 4 to 18 kg ha-1 from pea, and 46 to 69 kg ha-1 from GM residues. Therefore, when grain is harvested, the remaining crop residues do not release much N to the soil in the first year of decomposition, but the N stored in soil is presumably released in subsequent years. Key words: Crop residues, crop rotation, N mineralization, organic soil amendments
Influence of coarse wood and fine litter on forest organic matter composition
Authors: Krzyszowska-Waitkus Anna , Vance George F , Preston Caroline M.
Published: April 2011

Forest soil organic matter (SOM) is affected by inputs from coarse wood (CW) and fine litter (FL, e.g., leaves, twigs, cones, and needles). The influence of these materials on forest SOM was studied in a lodgepole pine (Pinus contorta) forest in southeastern Wyoming. Organic materials in CW sites were significantly (P < 0.05) more acidic, but contained half the total N of FL sites. Forest floor materials and SOM C contents were significantly greater in CW samples. Lignin decomposition products (CuO analysis) accumulated primarily in organic horizons of both sites, with significantly higher (60–70%) contents in CW materials. Vanillyl compounds were the primary lignin products from both sites, with cinnamyl compounds also important in SOM from FL sites. Vanillic acid to vanillin ratios were significantly higher in mineral soils under CW. 13C-NMR spectra indicated CW materials were enriched in lignin, and that humic acids from both site types were very similar and unusually high in alkyl C. Fulvic acids were also high in O-alkyl and carboxyl C, particularly in the CW sites. Results suggest there are differences in forest C constituents and that removal of CW could possibly alter forest soil dynamics that would impact forest productivity and biodiversity. Key words: Forest, coarse wood, litter, carbon, soil organic matter, humic substances
Potassium release during decomposition of crop residues under conventional and zero tillage
Authors: Lupwayi N Z , Clayton G W , O’Donovan J T , Harker K N , Turkington T K , Soon Y K
Published: April 2011

Nutrient cycling is an important part of integrated nutrient management. The litterbag method was used in field experiments to determine potassium (K) release patterns from red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues under conventional and zero tillage from 1998 to 1999 and from 1999 to 2000. Potassium contained in crop residues ranged from 25 kg ha-1 in wheat to 121 kg ha-1 in pea residues, both under zero tillage. The percentage of K released over a 52-wk period ranged from 65% of pea K under zero tillage to 99% of clover K under conventional tillage, and the amounts released were 20–32 kg ha-1 from wheat, 31–52 kg ha-1 from canola, 28–79 kg ha-1 from pea, and 31–118 kg ha-1 from legume GM residues. In both trial periods, K from wheat residues was released at a faster rate under conventional tillage than under zero tillage during the first 10 wk of residue decomposition. In contrast, K from pea and canola residues was released more quickly under zero tillage than under conventional tillage. The effect of tillage on K release from GM residues was similar to that on pea and canola residues in 1998–1999, but similar to that on wheat residues in 1999–2000. Correlations between K release and residue quality were inconsistent, presumably because K is not a structural component of plant tissue, and therefore its release is probably related more to leaching than to residue decomposition. These results show that crop residues recycle substantial amounts of K for use by subsequent crops in rotation. Key words: Conservation tillage, crop residue quality, crop rotation, organic soil amendments
Simulation of soil water content on a small reclaimed watershed in northern Alberta using the Root Zone Water Quality Model (RZQWM)
Authors: Mapfumo E. , Chanasyk D S , Chaikowsky C. L.A.
Published: April 2011

A study was conducted at Syncrude Canada Ltd., Alberta, to evaluate the simulation of soil volumetric water content from the reclaimed slopes of the Southwest Sand Storage Facility using the Root Zone Water Quality Model (RZWQM). Soil water content measurements were conducted every 2 wk using a neutron moisture meter in 2001 (dry year) and 2002 (wet year). Two types of calibration and evaluation were performed: first, calibration using 2001 weather data (dry year) and evaluation using 2002 weather data (wet year) (herein referred to as method 1); second, calibration using 2002 weather data (wet year) and evaluation using 2001 weather data (dry year) herein referred to as (method 2). Results from the method 1 calibration for each tube indicated modeling efficiencies (EF) between −0.27 and 0.90, coefficients of determination (r2) between 0.13 and 0.97, and deviation (D, as %) of simulated from measured values of less than 5%. The model evaluation by tube location following method 1 calibration indicated EF values between −3.80 and 0.56, whereas r2 values ranged between 0.08 and 0.82. Although five out of eight tubes had D values > 5%, all except for one tube had D values < 20%. Method 2 calibration results for each tube indicated EF values of −0.34 to 0.85, r2 values of 0.07 to 0.85 and all D values < 5%. Results of the method 2 model evaluation by tube location indicated EF values of −10.15 to 0.75 (overall EF = −0.84), r2 values of 0.04 to 0.96 (overall r2 = 0.39) and D values of 2.6 to 48.6% (overall D = 19.8). Method 2 model evaluation results indicated EF values of −1.69, −3.85 and −0.01, for depths of 15, 25 and 35 cm, respectively. The D values were 27, 20 and 13%, respectively. Graphical displays indicated that during the evaluation process, the model generally tended to slightly under-estimate the wetter moisture conditions, regardless of whether data for a wet year or a dry year were used during the calibration process. Key words: Modeling, calibration method, soil water, land reclamation
Particle densities of wetland soils in northern Alberta, Canada
Authors: Redding T. E. , Devito K. J.
Published: April 2011

Particle density is a fundamental soil physical property, yet values of soil and organic matter particle density (ρs and ρo) vary widely in the literature. We measured particle density of organic soils from five wetland types, and from exposed sediments of drying ponds, in northern Alberta, Canada. Our measured values of organic soil and pond sediment ρs varied widely (1.43–2.39 Mg m-3); however, calculated values of ρo (1.34–1.52 Mg m-3) were relatively constant. The measured and calculated ρs and ρo values were similar to those obtained in published studies using similar methods, but were higher than the values provided in many reference texts. Given the relatively small variability in ρo, the use of mean values of ρo, combined with measurements of organic matter loss-on-ignition, shows promise as a simple method for obtaining reliable estimates of ρs across a range of wetland types. Key words: Particle density, peat, organic matter, wetland soil, loss-on-ignition
Some characteristics of soil respiration in hybrid poplar plantations in northern Alberta
Authors: Saurette D. D. , Chang S. X. , Thomas B. R.
Published: April 2011

Fast-growing hybrid poplars are being planted in the Canadian prairies to meet the increasing demand for fibre and environmental services of trees and forests; however, the impact of hybrid poplars on C dynamics and storage on previously farmed land is largely unknown for the boreal region. We measured soil CO2 efflux along a chronosequence (3-, 9-, and 11-yr-old stands) of hybrid poplar (Populus deltoides × Populus × petrowskyana var. Walker) plantations and a control agricultural field from June to August 2004. Measurements were made between 0800 and 1800 with a portable Li-Cor 6400-09 system and were based on 4–5 min averaging. We also measured the response to simulated rainfall and the diurnal fluctuation of soil CO2 efflux. Soil CO2 efflux ranged from 1.30 µmol CO2 m-2 s-1 in the 3-yr old plantation to 5.41 µmol CO2 m-2 s-1 in the agricultural control field, or from 0.17 ìmol CO2 m-2 s-1 kg-1 C (based on soil organic C content to a 0.4 m depth) in the 3-yr-old plantation to 1.09 µmol CO2 m-2 s-1 kg-1 C in the 11-yr-old plantation. Simulated rainfall applied in the 3-yr-old plantation and a newly planted site resulted in an immediate pulse of CO2 efflux, 2.90 and 2.54 µmol CO2 m-2 s-1, respectively, followed by an efflux rate sustained slightly above pre-irrigation levels. No secondary pulse of soil respiration was observed in the 2-h period following water application. Diurnal variation of soil respiration was found to be small between 0600 and 1900 in the agricultural control field, with values that varied from 2.66 to 3.17 µmol CO2 m-2 s-1. Continued monitoring of soil respiration and other C cycling processes in the chronosequence will improve our understanding of the potential for C sequestration in hybrid poplar plantations in northern Alberta. Key words: Carbon sequestration, greenhouse gas emissions, biomass, boreal forest, land-use change, hybrid poplar
Dynamics of soil water-extractable organic C following application of dairy cattle manures
Authors: Angers Denis A , Chantigny Martin H , Rochette Philippe , Gagnon Bernard
Published: April 2011

Water-extractable organic C (WEOC) is a determinant driver of several soil and environmental processes, and can be influenced by management practices such as organic amendment. Our objective was to study the dynamics of soil WEOC following application of liquid and solid dairy cattle manures to a loamy and a clay soil under field conditions. Manures were applied in 2 consecutive years to silage corn fields at rates equivalent to 150 kg total N ha-1. Soil WEOC was monitored the day after application and weekly or biweekly thereafter in manured and control (mineral fertilizers) plots. Liquid and solid manure S brought on average 39 and 13 g WEOC m-2, respectively. These amounts are much larger than the increases measured in soil WEOC during the hours and days following manure application (0 to 30 mg kg-1, equivalent to 0 to 3 g m-2). Moreover, manure addition had little effects in the 10- to 30-cm soil layer. The rapid and extensive adsorption of manure WEOC onto mineral surfaces likely explains the limited effects of manure on soil WEOC. This adsorption process was presumably exacerbated by the mixing of manure and soil resulting from the tillage operation. Soil temperature and respiration appeared to have determinant influence on the level of soil WEOC content in the post-harvest period. Overall, temporal variations in soil WEOC contents were large and generally greater than the fluctuations directly attributable to manure addition. Key words: Soil organic C, extractable C, dairy manure, silage corn
Measuring greenhouse gas emissions from point sources in agriculture
Authors: McGinn S M
Published: April 2011

Carbon dioxide, methane and nitrous oxide emissions from agricultural sources have a significant role in the overall enhancement of the global greenhouse gas (GHG) effect. In research, measurements of GHG emissions are made to improve upon emission factors used in national inventories, identify and promote mitigation practices, and drive policy on GHG emissions in agriculture. These measurements are fundamental to the process of better management of GHG emissions. There is a variety of measurement techniques used in GHG research depending on the measurement environment and available resources. Techniques that use chambers or micrometeorological measurements are commonly employed for calculating emissions of GHG from point sources in agriculture, such as livestock and manure-holding facilities. This review examines these techniques, their limitations, and discusses methods to quantify their accuracy and precision. Emerging techniques like the use of dispersion models provide opportunities to directly determine emissions from whole farms. A few micrometeorological techniques (integrated horizontal flux and mass difference) are ideal for point sources such as manure storage facilities. For smaller sources, chambers are still recommended. In designing GHG emission studies, employing more than one technique when measuring GHG emissions is recommended, as often differences can exist due to technique. Ideally, a controlled release of the target gas, and its recovery, should also be conducted to evaluate techniques prior to their application. Although many techniques are often sensitive enough to quantify mitigation practices, i.e., the relative change in emissions, it is more difficult to determine “ true”emission factors as required for inventory work. It follows that the precision and accuracy of the techniques must accompany their application when estimating GHG emissions. Key words: Greenhouse gas, techniques, chambers, methane, agriculture, cattle
Response of high density apple orchards on coarsetextured soil to form of potassium applied by fertigation
Authors: Neilsen G H , Neilsen D.
Published: April 2011

This study tested the effects of fertigated potassium sources on orchard cation status. A randomized, complete block experimental design was maintained from 2000 to 2003, in a high density ‘Jonagold’/M.9 apple (Malus × domestica Borkh.) orchard planted in 1993 on a loamy sand. Seven K-fertigation treatments included annual application of either no K (control), 15 g K/tree as either potassium chloride or potassium magnesium sulphate (KMag) or 30 g K/tree as potassium chloride, KMag, potassium sulphate or potassium thiosulphate, applied daily during 6 wk midsummer to six replicate, four-tree plots. Fertigated K-forms did not affect yield, but increased soil K after 3 yr to 30-cm depth beneath the drip emitters. This increased leaf and fruit K concentrations. Fruit K/Ca ratio was also increased by K-fertigation. A high incidence of bitter pit at harvest was unaffected by fertigating K, but rather was associated with low harvest fruit Ca concentration and large fruit size. KMag increased soil Mg availability, but leaf and fruit Mg concentrations were slightly affected, indicating the difficulties of improving apple Mg status when co-applying K. Leaf and fruit Ca concentrations were minimally affected by treatments. Soil Ca declined slightly after 3 yr of K fertigation. Key words: Bitter pit, calcium, chloride, magnesium, Malus × domestica, sulphate, thiosulphate
Soil supply and nutrient demand (SSAND): A general nutrient uptake model and an example of its application to forest management
Authors: Comerford N B , Cropper, Jr. W P , Li Hua , Smethurst P J , Van Rees K. C.J. , Jokela E J , Adégbidi H. , Barros N F
Published: April 2011

Models of soil nutrient bioavailability and uptake assist in nutrient management and lead to a better understanding of nutrient dynamics in the soil-plant system. SSAND (Soil Supply and Nutrient Demand) is a steady state, mechanistic nutrient uptake simulation model based on mass flow and diffusive supply of nutrients to roots. It requires user inputs for soil and plant parameters to calculate a nutrient’s concentration at the root surface and the subsequent uptake by a plant root and/or extrametrical mycorrhizal hyphae. It can be considered a sub-model linked to hydrological or plant growth models. SSAND provides a basis for simulating nutrient uptake under different soil-plant scenarios, including multiple soil compartments, net mineralization inputs, changing root growth, changing mycorrhizal hyphae growth, changing soil water content and multiple fertilizer events. It incorporates uptake from roots and mycorrhizal hyphae, including the potential competition between these entities. It should be useful for simulating the effects of climate change on soil nutrient bioavailability. It should also be a useful tool for managers in evaluating fertilizer regime options. Key words: Nutrient bioavailability, nutrient uptake modeling, phosphorus uptake, mycorrhizae, Spodosols, climate change
Seafood processing wastes as nutrient sources for crop production
Authors: MacLeod J A , Kuo S. , Gallant T L , Grimmett M.
Published: April 2011

Large quantities of wastes are generated in the processing of seafood such as shellfish, crustaceans and finfish. These materials contain appreciable amounts of plant nutrients which may be useful in cropping programs. Under some conditions the waste materials can be directly applied to soil but in other situations stabilization may be necessary. The method of stabilization will influence the availability of nutrients in various cropping programs. Composting with wood can effectively stabilize the waste but the slow mineralization of organic N can limit the usefulness of the compost. Combining the waste with calcium oxide (CaO) or hydrated lime [Ca(OH)2] can produce a stable material with good nutrient availability. If application rates of various wastes are based on their nutrient content, the nutrient requirement of specific crops, and the heavy metal concentrations, then potential environmental problems associated with excess nutrient and heavy metal loadings can be minimized. Application of these materials to land can effectively supply nutrients to crops and minimize environmental damage due to inappropriate methods of disposal. Key words:Seafood waste, composting, lime stabilization, crop nutrients
Soil organic carbon content in northern Canada: A database of field measurements and its analysis
Authors: Hossain M. F. , Zhang Yu , Chen Wenjun , Wang Jixin , Pavlic Goran
Published: April 2011

Arctic and sub-arctic soils contain a large amount of organic carbon in their topsoil horizons and in the upper layers of permafrost. There is concern that climate warming could release this soil organic carbon (SOC) to the atmosphere as greenhouse gases. However, information about the profile features and spatial distribution of SOC in northern ecosystems are far less than for other regions. In this study, we compiled all the available field measurements of SOC in northern Canada and developed a database. Including our recent measurements, the database contains 438 profiles with 1473 soil horizons. We analyzed the profile features and the regional patterns of SOC in northern Canada based on this database. The results show that the SOC content of subsurface soils is relatively high in northern regions because of the alternate freeze-thaw actions. In the top 100 cm of soils, 40% of the SOC is located in the 50- to 100-cm layer. The SOC content is lower in northern Arctic and in mountainous regions. The average upland SOC content in northern Canada is higher than in other world biomes (i.e., croplands, temperate forest, tropical savannas, and tropical forest) except temperate grasslands and boreal forest. Key words: Soil organic carbon, northern Canada, database, arctic and sub-arctic.
Residual soil nitrogen indicator for agricultural land in Canada
Authors: Drury C F , Yang J Y , De Jong R. , Yang X M , Huffman E C , Kirkwood V. , Reid K.
Published: April 2011

Residual soil nitrogen (RSN) is the amount of inorganic nitrogen that remains in the soil at the end of the growing season after crops have been harvested. RSN is an estimate of this quantity, calculated as the difference between all N inputs (fertilizer, manure-N, biological fixation, and atmospheric deposition) and all N outputs (N removed in crop harvest, N lost from ammonia volatilization and N lost from denitrification) assuming that mineralization and immobilization are generally balanced. RSN was calculated on a soil polygon level (scale 1:1 million) as well as on provincial and national levels for each of the 5 census years from 1981 to 2001. The Canadian average RSN values from 1981 to 1996 were fairly constant with a range of 12.9 to 13.9 kg N ha-1. However, RSN increased by 51% from 13.9 kg N ha-1 in 1996 to 21.0 kg N ha-1 in 2001. This dramatic increase was due to several factors including an increase in legume crop acreage (i.e., increased biological N2 fixation) and lower crop yields and reduced N uptake as a result of climatic constraints (droughts) which were prevalent in many regions in Canada in 2001. Key words: Nitrate, residual nitrogen, nitrogen balance, N indicator
Automation and evaluation of three pesticide fate models for a national analysis of leaching risk in Canada
Authors: McQueen D. A. R. , Farenhorst A. , Allaire S. , Cessna A J
Published: April 2011

Under the National Agri-Environmental Health Analysis and Reporting Program (NAHARP), pesticide fate models are being used to develop an indicator of risk of water contamination by pesticides (IROWC-Pest) in Canada. The large number of model runs needed for a national analysis of the risk of pesticide leaching to ground water required the development of a computer program, AutoPFM (Automate Pesticide Fate Model), to automate the running of pesticide fate models. Using Manitoba as a test province, and the selected pesticide fate models PRZM, LEACHP, and MACRO, AutoPFM permitted the estimation of the leaching potential of the fourteen most used agricultural pesticides in Manitoba. Assuming an application rate of 300 g ha-1 for each pesticide, only six pesticides demonstrated leaching across most soil series. For these six pesticides, there was significant correlation in how PRZM and LEACHP ranked the leaching potential of 337 Manitoba soil series. Because of its long running times, the estimation of leaching potential with MACRO was limited to two pesticides (2,4-D and MCPA). For these pesticides, MACRO showed significant correlation with the PRZM and LEACHP in ranking the soil series. Based on the results described in this paper, PRZM was chosen as the pesticide leaching model for use in IROWC-Pest. Key words: Risk indicators, pesticide, PRZM, LEACHM, LEACHD, MACRO, model automation, leaching, soil
Application of a risk indicator for assessing trends in dryland salinization risk on the Canadian Prairies
Authors: Wiebe B H , Eilers R G , Eilers W D , Brierley J A
Published: April 2011

Moderate to severe soil salinity currently affects the surface 60 cm of approximately 1 million ha within agricultural regions of the prairies. The subsoil (60–120 cm) is affected on about 3.5 million ha. The risk of soil salinization (RSS) indicator was developed to measure and monitor the change in risk of soil salinization in the Canadian Prairies as a function of changes in agricultural land use and management practices as reported in the Canadian Census of Agriculture. We have expressed the RSS indicator in five classes from very low to very high risk. In 1981, 18.4% of the land area in the agricultural regions of the prairies was rated as having a moderate or higher risk of salinization. By 2001 this had improved to less than 12% (8 million ha). Prairie-wide the land area at high and very high risk of salinization decreased from 6.2 to 4.4% of agricultural landscapes and the area at moderate risk decreased from 12.2 to 7.3%. We attribute this improvement largely to a reduction in summer fallow with a minor contribution from increased use of permanent cover. Although the risk of soil salinization is far from eliminated, the trend is towards greater agri-environmental sustainability. Key words: Risk of soil salinization, dryland salinity, land use, summer fallow, permanent cover
Natural attenuation of diesel fuel in heavy clay soil
Authors: Berry Karin A. T. , Burton David L.
Published: April 2011

Petroleum hydrocarbons in the extractable fraction decreased rapidly in a heavy clay soil contaminated with diesel fuel at 5000 mg kg−1 demonstrating natural attenuation. Natural attenuation rates for untilled soil were estimated using two distinct extraction and analysis methods, the Oil & Grease Content (O&G) (US EPA 418.1; ASTM D 95) and extractable organics (EO) (EPA 3520B; EPA 8000A). The time to 50% decrease (t1/2) in the fraction varied with extraction method, Oil & Grease Content (11 d) and Extractable Organics (26 d). Complete attenuation appeared to have occurred after 74 d as Extractable Organic values for soil extracts were below the detection limit (5 µg g−1). An enzyme-linked immunosorbant assay (ELISA) was also used to monitor the hydrocarbons present in the soil. This also effectively demonstrated the near-complete disappearance of the hydrocarbons but was not quantitative. Soil microbial biomass carbon (chloroform fumigation-extraction) and surface CO2 flux measurements did not show any significant impact of diesel contamination or tillage in the active microbial population. This observation serves to demonstrate the applicability of natural attenuation as a remedial strategy for heavy clay soils contaminated with diesel fuel of the type used in this study.

Key words: Natural attenuation, bioremediation, diesel fuel, enzyme-linked immunosorbant assay, heavy clay soil
Evaluation of EPIC's snowmelt and water erosion submodels using data from the Peace River region of Alberta
Authors: Puurveen H. , Izaurralde R. C. , Chanasyk D. S. , Williams J. R. , Grant R. F.
Published: April 2011

Water erosion due to snowmelt is a major form of erosion in boreal regions of the Canadian Prairie. Evaluation of erosion models is an essential step before recommending their use in local or regional assessments of erosion rates and control methods. Using inputs from a runoff study conducted at La Glace, Alberta (55°25'N, 119°10'W) from 1984 to 1986, we evaluated the Erosion-Productivity Impact Calculator (EPIC) for its ability to simulate runoff and sediment yield from snowmelt events. The model was initialized with soil profile data acquired at the study site and complemented with data from standard soil databases (Albright series; loam, Dark Gray Chernozem). Daily weather data were acquired from the nearest climatological station (annual precipitation = 475 mm). Management data were as reported and included combinations of conventional and reduced tillage, annual and perennial, and fallow cropping. Mean runoff volume measured in 1985 was 57 mm while in 1986 it was 76 mm. EPIC over-predicted runoff volume by 25% in 1985 but under-predicted it by 7% in 1986. The period in which snowmelt occurred (mid-March – beginning of April) was predicted correctly. Under the conditions of this study, with many cropping inputs obtained from different sources, the model was unable to reproduce the reported management effects on runoff and sediment yield. EPIC simulated springmelt soil temperature trends at 9-cm depth, although the predicted temperatures in 1985 were generally underestimated. Our results suggest that the EPIC model calculates adequate values of runoff volumes and sediment yields during snowmelt.

Key words: Runoff, sediment yield, soil erosion, crop rotations
Regional simulation of fall and spring soil moisture in Alberta
Authors: Akinremi O. O. , McGinn S. M. , Howard A. E.
Published: April 2011

The recurrence of agricultural drought on the prairies has increased the demand for soil moisture information by farmers, regional planners and supporting sectors of agriculture. In response, estimation of regional soil moisture by soil survey is conducted despite its being resource intensive and having limited resolution in time and space. Models that estimate soil moisture on a regional scale would contribute to the evaluation of regional water deficits and overcome problems related to conducting field surveys. This study uses a modified version of the versatile soil moisture budget to estimate available soil moisture within the root zone on a regional scale. The spatial pattern of modelled soil moisture in the fall was similar to that mapped by soil survey. Of the 145 grid points compared, agreement between modelled and field survey was 60% or higher in 5 out of 8 yr. However, too few years of data were available for a reliable assessment of model performance in the spring. The simulated soil moisture was sensitive, and directly related to the value used for available water capacity (AWC). Accurate values of AWC are necessary for accurate simulation of regional soil moisture.

Key words: Soil moisture, modelling, water capacity, regional estimates, Canadian prairies
Temperature of upland and peatland soils in a north central Minnesota forest
Authors: Nichols Dale S.
Published: April 2011

Soil temperature strongly influences physical, chemical, and biological activities in soil. However, soil temperature data for forest landscapes are scarce. For 6 yr, weekly soil temperatures were measured at two upland and four peatland sites in north central Minnesota. One upland site supported mature aspen forest, the other supported short grass. One peatland site was forested with black spruce, one supported tall willow and alder brush, and two had open vegetation — sedges and low shrubs. Mean annual air temperature averaged 3.6 °C. Mean annual soil temperatures at 10- to 200-cm depths ranged from 5.5 to 7.6 °C among the six sites. Soils with open vegetation, whether mineral or peat, averaged about 1 °C warmer annually and from 2 to 3 °C warmer during summer than the forested soils. The tall brush peatland was cooler than all other sites due to strong groundwater inputs. The mineral soils warmed more quickly in the spring, achieved higher temperatures in the summer, and cooled more quickly in the fall than the peat soils; however, the greatest temperature differences between mineral and peat soils occurred at or below 50 cm. In the upper 20 cm, vegetation and groundwater had greater effects on temperature than did soil type (mineral or peat). Summer soil temperatures were higher, relative to air temperature, during periods of greater precipitation. This effect was minimal at upland sites but substantial in the peatlands. In spite of the persistent sub-freezing air temperatures typical of Minnesota winters, significant frost developed in the soils only in those years when severe cold weather arrived before an insulating cover of snow had accumulated. Key words: Soil temperature, vegetation effects, forest soils, groundwater, peatlands
Nitrogen dynamics in soils with different hydrocarbon contents planted to barley and field pea
Authors: Xu J. G. , Johnson R. L.
Published: April 2011

Nitrogen dynamics and cycling are important in plant-soil ecosystems, and they may differ between hydrocarbon-contaminated and uncontaminated soils. The objective of this experiment was to study the effects of petroleum hydrocarbons and remediation methods on nitrogen dynamics and cycling in plant-soil ecosystems. The experiment involved two plant species (barley and field pea) grown in soils at four different hydrocarbon levels (0, 5, 25 and 55 g kg−1). Hydrocarbon contamination significantly reduced N uptake by plants, but increased N accumulation in soil microbial biomass. It widened the C:N ratio in soil and led to more available N being immobilized by soil microorganisms, which reduced available N for plantuptake. Urease activity increased with hydrocarbon content in soil due to the increase of microbial biomass and activity.

Key words: Nitrogen dynamics, hydrocarbon contamination, microbial activity, remediation, Black Chernozem
Étude des interactions entre trois espèces d'Acacia (Faidherbia albida Del., A. seyal Del., A. holosericea A Cunn. ex G. Don) et Meloidogyne mayaguensis au Sénégal
Authors: Duponnois R. , Tabula T. K. , Cadet P.
Published: April 2011

The susceptibility of three Acacia species used in Senegal (F. albida Del., A. seyal Del. and A. holosericea A Cunn. Ex G. Don) to M. mayaguensis is studied after inoculation of the nematode at different stages of seedling development (seedling stage, cotyledon and young leaves). The observation of giant cells induced by M. mayaguensis on all three Acacia species testifies to their susceptibility to the nematode. However the pathogenic effect of M. mayaguensis on the growth of A. holosericea and A. seyal is more important than on F. albida. Moreover, the penetration and the development of the nematode is greater with these two Acacia species. The susceptibility of Acacia decreased when nematodes are inoculated on older seedlings. These results indicate that some Acacia sp. used to restore soil fertility will multiply parasites susceptible to infest subsequent crops.

Key words:Acacia spp., Meloidogyne mayaguensis, Rhizobium, pathogenesis, histopathologynot available
Characterization of disaggregated nonwettable surface soils found at old crude oil spill sites
Authors: Roy Julie L. , McGill William B.
Published: April 2011

We characterized some of the physical, chemical, and microbiological properties of soils that have become severely water-repellent and disaggregated several years or decades following oil contamination. A growing number of patches (usually <2 ha) of disaggregated water-repellent soils have recently been discovered throughout the province of Alberta at 20 to 50-yr-old crude oil spill sites. The disaggregated water-repellent soil is usually confined to a dry and powdery surface layer 10 to 15 cm deep, which no longer smells, feels, or looks like it contains any oil. These soils appear to have permanently lost the ability to support plant growth and recover through natural processes. We analyzed samples of disaggregated water-repellent and adjacent normal soils from three old crude oil spill sites to provide a background set of information about these poorly known soils and assist in the development of hypotheses concerning the development and persistence of soil water repellency and structural degradation. Compared with normal adjacent soils, disaggregated nonwettable soils are characterized by: (1) a strong resistance to wetting, as determined by the molarity of ethanol droplet (MED) test; (2) a smaller population of viable and culturable microorganisms, which contains at least some representatives from nonspore-forming bacterial genera; (3) a high content of mineral N and total C, a comparable pH and ratio of exchangeable cations, but a lower cation exchange capacity; (4) a slightly lower clay content, as determined by the Bouyoucos hydrometer method; (5) a comparable water desorption behaviour following forced saturation with water; (6) dry aggregates of a smaller mean weight diameter (MWD), as determined by dry sieving and scanning electron miscroscopic (SEM) analyses; (7) slightly less pronounced thermal reactions when heated up to 525 °C, as determined by differential thermal analyses (DTA); and (8) a reduced ability to support plant growth. From these observations, we infer that disaggregated water-repellent soils found at old crude oil spill sites do not differ appreciably from normal adjacent soils in terms of their inorganic chemistry. Nonwettable and adjacent wettable soils differ mostly in terms of some physical and biological characteristics, which probably stem from differences in the quality of the organic matter they contain. Key words: Crude oil spills, petroleum hydrocarbons, soil water repellency, soil disaggregation, soil hydrophobicity
Redistribution of extractable nutrients following disc trenching on Luvisols and Brunisols in Saskatchewan
Authors: Nesdoly R. G. , Vanrees K. C. J.
Published: April 2011

Disc trenching is an important silvicultural management tool for creating microsites to ensure the survival and growth of newly planted seedlings. Mounded microsites are thought to be a source of nutrients for seedling roots; however, little is known concerning how nutrients are redistributed in the soil after disc trenching. The objective of this study, therefore, was to determine the redistribution of soil horizons and selected soil chemical properties following Delta disc trenching. Three sites were selected on both Luvisol and Brunisol soils in northern Saskatchewan. Soil profiles were excavated and samples collected from 15 × 5 cm grids to a 1-m depth. Samples were analyzed for pH and extractable nitrate (NO3), ammonium (NH4), phosphorus (P), potassium (K) and sulfur (S). Disc trenching concentrated extractable N, P and S in the berm microsite compared to the trench microsites. The redistribution of extractable NO3, NH4 and P in the berms compared to the trench microsites was 20 times greater for Luvisol sites compared to the Brunisol sites, while extractable K and S were similar between both microsites for each soil. Seedlings planted on these mounded microsites therefore should have a large pool of nutrients for plant growth; however, further work is needed to determine patterns of nutrient uptake by seedlings in relation to mounded and trench microsites. Key words: Delta disc trenching, boreal forest, Luvisols, Brunisols, nutrients
Fly ash influence on near-surface temperature of a clay loam soil
Authors: Hammermeister A. M , Chanasyk D. S. , Naeth M. A.
Published: April 2011

It has been suggested that fly ash, when applied as a soil amendment, would increase soil temperature. However, no quantitative data have been provided to support this hypothesis. This hypothesis was tested on four fly ash treatments (0, 100, 200, and 400 t ha−1) applied to clay loam soil in a randomized block design. Bi-hourly soil temperatures were measured on 3 summer days over 2 yr, and afternoon temperatures were measured on randomly selected spring days at 5-, 10-, and 20-cm depths in the four fly ash treatments. Temperatures were measured in conjunction with surface bulk density, water content, and particle size distribution which were also used to calculate thermal heat capacity. Fly ash decreased percent clay, soil water content, and soil heat capacity. Contrary to previously expected trends, fly ash amendment did not significantly increase mean daily soil temperature under dry conditions. Generalizations in the literature regarding the influence of fly ash on soil temperature, bulk density, and water-holding capacity must be considered carefully since they generally relate only to coarse to medium textured soils. Key words: Soil amendments, bulk density, reclamation, heat capacity, thermal diffusivity, thermal conductivity, volumetric water content, particle size distribution
Estimating spring wheat yield variability with EPIC
Authors: Roloff G. , Jong R. de , Zentner R. P. , Campbell C. A. , Benson V. W.
Published: April 2011

The Environmental Policy Integrated Climate (EPIC) model has been used on the semiarid temperate Canadian Prairies to estimate crop yield, soil erosion loss, and water and nitrate dynamics. While its estimates of long-term average yields are accurate for most purposes, additional model development is desirable to fully reflect year-to-year variability. We tested the precision of EPIC (version 5300) in estimating mean yields and in replicating yearly yield variability as influenced by the potential evapotranspiration (PET) method, using field data from a 27-yr crop rotation experiment at Swift Current, Saskatchewan. Rotations tested ranged from continuous wheat (Triticum aestivum L.) to fallow-wheat-wheat. Mean estimated yields were compared with measured yields (MY) and detrended yields (DY). Estimated yields and MYs were further compared by regression, ratio of variances due to lack-of-fit and to experimental errors (R), and model efficiency (EF). Mean yields estimated using the Penman-Monteith and the Priestly-Taylor PET methods resulted in significant underestimations, associated with high annual PET values, and were not analysed further. The Hargreaves (H) and Baier-Robertson (BR) PET methods resulted in mean yields not different than MY or DY for most cases, especially the BR method. EPIC with the H method accounted for 18 to 66% of the variability in annual yield estimation, whereas the BR method accounted for 29 to 60%. These were slightly, but not significantly, lower than results obtained with regionally derived statistical crop models. Overall EPIC with the BR PET method provided yield estimates accurate and precise enough for long term studies. The relatively high R and low EF values obtained, though, suggest further improvements in EPIC are necessary to better replicate yearly yield variability. Analysis of yield residuals indicated that EPIC may not be simulating accurately enough the water balance and its effects throughout the off-season and in the early part of the growing season. Key words: Semiarid temperate climate, crop model, potential evapotranspiration
Runoff and sediment yield from snowmelt and rainfall as influenced by forage type and grazing intensity
Authors: Gill S. I. , Naeth M. A. , Chanasyk D. S. , Baron V. S.
Published: April 2011

Currently, there is interest in Western Canada in extending the grazing season using perennial and annual forages. Of greatest concern is the environmental sustainability of these grazing systems, with emphasis on their ability to withstand erosion. A study to examine the runoff and sediment yields of annual and perennial forages in central Alberta was initiated in 1994. Runoff and sediment yield were quantified under snowmelt and rainfall events for two seasons. Rainfall simulation was used to further examine runoff under growing season conditions. Four forage treatments (two annuals: triticale and a barley/triticale mixture and two perennials: smooth bromegrass and meadow bromegrass) and three grazing intensities (light, medium and heavy) were studied, each replicated four times. Total annual runoff was dominated by snowmelt. Generally runoff volumes, sediment yields, sediment ratios and runoff coefficients were all low. Bare ground increased with increasing grazing intensity and was significantly greater in annuals than perennials for all grazing intensities. Litter biomass decreased with increasing grazing intensity and was generally similar in all species for both years at heavy and medium grazing intensities. Results from the rainfall simulation corroborated those under natural rainfall conditions and generally indicated the sustainability of these grazing systems at this site. Key words: Forages, soil erosion, sustainability, rainfall simulation