bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil carbon: A measure of ecosystem response in a changing world?
Authors: Janzen H. H.
Published: April 2011

The global carbon (C) cycle is changing, as evident from abrupt increases in atmospheric CO2. These changes have sparked interest in agricultural soils as potential repositories for excess atmospheric C. Our perspective on soil C, therefore, has shifted: once, we focused mainly on how soil C affected productivity within agroecosystems; now we see also how C dynamics in agricultural soils exert influences far beyond the farm. We have long used soil C as an indicator of soil quality; now we may want to use soil C also as a broader indicator of ecosystem response. To prompt further discussion, I offer some tentative thoughts about how we might use soil C as an indicator on a changing earth. They include: using soil C to measure changes across time, not only across space; devising more sensitive measures of soil C change; quantifying soil C across four dimensions; measuring the nature of C, as well as its amount; using soil C alongside other indicators; finding better ways of admitting our uncertainty; establishing long-term sites for our successors to measure soil C change; and following flows of C past the farm fences. Recent worries about global warming have focused our attention on “sequestering” soil C to remove atmospheric CO2. That aim may be worthy, but perhaps too narrow; a broader goal might be to ensure the productivity, permanence, and health of our agroecosystems and adjacent environments – and use C storage as a measure of progress toward that goal. Key words: Soil organic matter, global carbon cycle, carbon sequestration, global change
An empirical model for estimating carbon sequestration on the Canadian prairies
Authors: Liang B. C. , Campbell C. A. , McConkey B. G. , Padbury G. , Collas P.
Published: April 2011

There is a need to develop verifiable algorithms that can be easily applied to estimate carbon sequestration in soils. A simple process-based empirical model, driven primarily by soil texture and crop residue input, was developed to account for changes in soil organic carbon (SOC) in Chernozemic soils on the Canadian prairies. The model was used to estimate SOC change under no-till and continuous cropping compared with conventional tillage and rotations with fallow. Using this model, C sequestration due to continuous cropping compared with fallow-containing rotations was determined to be 0.09 Mg C ha-1yr-1 for the Brown and Dark Brown, and 0.05 Mg C ha-1 yr-1 for the Black and Dark Gray/Gray soil zones. The rate of C sequestration as a result of continuous cropping was positively related to the frequency of fallow, which decreases on the prairies from the Brown, Dark Brown, and Black to the Dark Gray/Gray soil zones. Using this model average C sequestration when conventional tillage was converted to no-till, was 0.13, 0.23, 0.34, and 0.25 Mg C ha-1 yr-1 for the same soil zones, respectively. Combined gains due to no-till and continuous cropping in comparison with conventional tillage and fallow-containing rotations were determined to be 0.22, 0.32, 0.39, and 0.30 Mg C ha-1 yr-1 for the Brown, Dark Brown, Black and Dark Gray/Gray soil zones, respectively. Based on Agricultural Census of Canada data in 1996 and 2001, the amount of “C sequestered” due to the adoption of no-till was estimated to be 1.23 million Mg of C in 1996 and 1.72 million Mg of C in 2001, which is approximately 10% of the total greenhouse gas emissions from the agricultural sector in Canada. This simple process-based empirical model could serve as a useful tool for soil scientists to use in assessing soil sustainability and C sequestration in the Canadian prairies. It would also assist policy makers in understanding how various scenarios of improved management will influence future greenhouse gas emissions on agricultural soils. Key words: Soil organic carbon, no-till, fallow, crop rotation
Efficiency of fall-banded urea for spring wheat production in Manitoba: Influence of application date, landscape position and fertilizer additives
Authors: Tiessen K. H. D. , Flaten D. N. , Grant C. A. , Karamanos R. E. , Entz M. H.
Published: April 2011

A 2-yr study was conducted to investigate the effects of application date, landscape position and a urease and nitrification inhibited formulation of urea on the efficiency of fall-banded N fertilizer under Manitoba conditions. To date, no studies have investigated how these factors interact to influence the efficiency of fall-banded N in western Canada. The effects of landscape position were apparent at three of the four sites, with significantly greater grain yields, straw yields and total recovery of N in the high landscape positions than in the low landscape positions. In the high landscape positions, there were no significant differences in crop response or recovered N among application dates in the fall and spring. However, in the low landscape positions, grain yields, grain yield increases and apparent recovered fertilizer N in the aboveground portion of the crop and in the soil (0–120 cm) were significantly greater for spring and late fall applications, when compared with early and mid-fall applications. At one site in the first year of the study, early fall-banded N with the urease and nitrification inhibitors produced greater increases in grain yield than early fall-banded N without the inhibitors in the low landscape positions. However, overall there was little agronomic benefit to the use of the additives, as there were few significant differences in crop yields or N uptake by the crop with the inhibitors than without, in either year or landscape position. The results demonstrate that selection of suitable timing for application of fertilizer N to optimize crop yields is much more critical for poorly drained areas within a field, or for poorly drained fields, than for better drained land. Key words: Fall-banded N, spring-banded N, landscape position, N-(n-butyl) thiophosphoric triamide (NBPT), Dicyandiamide (DCD), wheat (Triticum aestivum)
Soil management effects on organic carbon in isolated fractions of a Gray Luvisol
Authors: Plante A. F. , Stewart C. E. , Conant R. T. , Paustian K. , Six J.
Published: April 2011

Agricultural management affects soil organic matter, which is important for sustainable crop production and as a greenhouse gas sink. Our objective was to determine how tillage, residue management and N fertilization affect organic C in unprotected, and physically, chemically and biochemically protected soil C pools. Samples from Breton, Alberta were fractionated and analysed for organic C content. As in previous reports, N fertilization had a positive effect, tillage had a minimal effect, and straw management had no effect on whole-soil organic C. Tillage and straw management did not alter organic C concentrations in the isolated C pools, while N fertilization increased C concentrations in all pools. Compared with a woodlot soil, the cultivated plots had lower total organic C, and the C was redistributed among isolated pools. The free light fraction and coarse particulate organic matter responded positively to C inputs, suggesting that much of the accumulated organic C occurred in an unprotected pool. The easily dispersed silt-sized fraction was the mineral-associated pool most responsive to changes in C inputs, whereas the microaggregate-derived silt-sized fraction best preserved C upon cultivation. These findings suggest that the silt-sized fraction is important for the long-term stabilization of organic matter through both physical occlusion in microaggregates and chemical protection by mineral association. Key words: Soil organic C, tillage, residue management, N fertilization, silt, clay
Estimating actual evapotranspiration using water budget and soil water reduction methods
Authors: Chanasyk David S , Mapfumo Emmanuel , Chaikowsky Crystal L.A.
Published: April 2011

Studies on estimation of actual evapotranspiration on disturbed lands are scarce and yet such data are essential in hydrologic modeling. Our study compared the variability of estimates of actual evapotranspiration (AET) from a reclaimed site in northern Alberta using the simplified water budget (WB) and soil water reduction (SWR) methods. The AET estimates from the simplified water budget equation (AET1) required field soil water content, precipitation and runoff. The AET estimates from the soil water reduction method (AET2) required daily potential evapotranspiration (PET), field capacity (FC) water content, minimum field-measured water content, and field water content. Soil water was measured using neutron moisture gauge every 2 wk during the growing season for a 2-yr period. The average AET1 and AET2 estimates for 2001 were 1.9 and 1.4 mm per day, respectively, where as those for 2002 were 2.1 and 1.2 mm per day, respectively. The paired t-tests to compare AET1 against AET2 indicated significance differences (P ≤ 0.05) in 5 out of 11 measurement dates, especially during high rainfall periods. Overall AET2 estimates were more variable than AET1 estimates. Therefore, the larger variability of AET2 estimates imply less reliability of spatially averaged AET2 estimates for use in regional and global circulation models. Key words: Extractable water, reclaimed land, water budget, soil water reduction, potential evapotranspiration
Biodegradation of caffeine in agricultural soil
Authors: John Hendel Edward Topp, , Lu Zexun , Chapman Ralph
Published: April 2011

Caffeine (1,3,7-trimethylxanthine) could represent a useful marker of contamination of effluent from agricultural land receiving biosolids. The persistence characteristics of caffeine in three agricultural soils was investigated. In laboratory microcosms of moist soil incubated at 30°C, [8-ring-14C]-caffeine was rapidly and thoroughly mineralized to 14CO2 in a sandy loam and a loam soil, and less rapidly in a silt loam soil. Caffeine mineralization was very responsive to soil temperature and moisture. Mineralization of caffeine was hastened by the addition of liquid municipal biosolids (LMB) from three municipal sewage-treatment plants (MSTPs) that aerate this material. In contrast, LMB from three MSTPs that did not aerobically digest their LMB did not accelerate caffeine mineralization. Autoclaved LMB had no effect on caffeine dissipation. Abacterium, designated Pseudomonas sp. Strain TH1, was isolated from aerated LMB. The bacterium first demethylated caffeine to 3,7-dimethylxanthine, and then mineralized the molecule. Inoculation of Pseudomonas sp. Strain TH1 into soil hastened mineralization of [8-ring-14C]-caffeine. In summary, caffeine was more stable in a silt loam soil than a sandy loam or loam soil, but biodegradation in all three soils was quite uniform upon the addition of caffeine-degrading bacteria or aerated biosolids. We suggest that caffeine would likely not be a suitably conservative chemical marker for detecting chronic contamination of agricultural drainage water following fertilization wit hLMB. Aerobic digestion of LMB promotes the enrichment of caffeine-degrading microorganisms. Key words: Caffeine biodegradation, biosolids chemical marker, biosolids organic contaminant, water quality
Agri-environmental models using Mehlich-III soil phospho rus saturation index for corn in Quebec
Authors: Pellerin Annie , Parent Léon -Étienne , Tremblay Catherine , Fortin Josée , Tremblay Gilles , Landry Christine P , Khiari Lotfi
Published: April 2011

Soil phosphorus (P), which is potentially a risk for environmental contamination, is currently interpreted using soil P saturation in North America. Our objective was to assess the ratio of P to aluminum (Al) in the Mehlich-III (M-III) soil test to build P requirement models for corn and soybean. We analyzed 129 corn and 19 soybean P fertilizer trials. For corn, the (P/Al)M-III ratio improved soil fertility classification compared with PM-III alone. The critical PM-III value as determined by the Cate-Nelson procedure was found to be 31.5 mg PM-III kg-1, close to published values. The critical (P/Al)M-III ratios of 0.025 for > 300 g clay kg-1 soils and 0.040 for ≤ 300 g clay kg-1 soils differed significantly between the two soil groups. For (P/Al)M-III ratios above 0.214, there was no positive response to added P for all soils regardless of texture. Using published critical environmental (P/Al)M-III ratios of 0.076 for > 300 g clay kg-1soils and 0.131 for ≤ 300 g clay kg-1 soils as benchmarks values, agri-environmental P requirement models were built using conditional expectations of 50 to 80% of computed optimum P values within a soil class. A validation study supported the low critical (P/Al)M-III ratios and the 50% conditional expectation model except for a high carbon soil which was outside the application range of the models. However, banded P decreased corn yield at four validation sites although the model predicted positive response to P. Soybean did not respond to P except at extremely low fertility levels ((P/Al)M-III ≤ 0.02) and behaved as a P-mining crop even in low-P soils. Corn-soybean rotations can reduce soil P to low (P/Al)M-III ratios with minimal agronomic risk. Key words: Soil phosphorus saturation, Mehlich-III soil extraction method, soil fertility classification, soil texture, fertilizer P requirement model, corn, soybean
Runoff phosphorus retention in vegetated field margins on flat landscapes
Authors: Sheppard S C , Sheppard M I , Long J. , Sanipelli B. , Tait J.
Published: April 2011

Vegetated buffer strips (VBS) are often recommended as a management practice that farmers can use to help mitigate the environmental effects of runoff from agricultural fields. Previous research has shown that VBS can be effective at trapping phosphorus (P) and other farm-sourced environmental contaminants. This project measured the effectiveness of established vegetated strips at decreasing P in runoff from agricultural fields in Manitoba. Paired samples of runoff, taken at the field edge and in the vegetated strip, indicated that in 11 of the 22 cases sampled (50%), P concentrations in the runoff decreased (on average 30%) as the flow passed through the vegetated strip. In 7 of the 22 case (32%) there was no difference; however, in four of the 22 cases (18%), runoff P concentrations increased, indicating the vegetated strip had become a source of runoff P. Soil samples from the VBS showed high available P concentrations at positions within the vegetated strip along the runoff flow path, and in 7 of 10 cases these concentrations were higher (33% on average) than in the field soil. Although the observations and numerical results suggest that VBS can be effective at removing P in runoff, perhaps the major limitation in this flat-land region is that runoff tends to flow through rather small portions of the VBS, and these may not have sufficient capacity to retain the runoff P in the longer term. Key words: Vegetated filter strips, VBS, VFS, manure, soluble, particulate, ortho, riparian
Projected changes in mineral soil carbon of European forests, 1990–2100
Authors: Jo Smith Pete Smith, , Jeannette Meyer Martin Wattenbach, , Sönke Zaehle Marcus Lindner, , Robert J.A. Jones Roland Hiederer, , Mark Rounsevell Luca Montanarella, , Reginster Isabelle , Kankaanpää Susanna
Published: April 2011

Forests are a major land use in Europe, and European forest soils contain about the same amount of carbon as is found in tree biomass. Changes in the size of the forest soil carbon pool could have significant impacts on the European carbon budget. We present the first assessment of future changes in European forest soil organic carbon (SOC) stocks using a dedicated process-based SOC model and state-of-the-art databases of driving variables. Soil carbon change was calculated for Europe using the Rothamsted Carbon model using climate data from four climate models, forced by four Intergovernmental Panel on Climate Change (IPCC) emissions scenarios (SRES). Changes in litter input to the soil due to forest management, projected changes in net primary production (NPP), forest age-class structure, and changes in forest area were taken into account. Results are presented for mineral soil only. Under some climate scenarios carbon in forest soils will increase slightly (0.1 to 4.6 Pg) in Europe over the 21st Century, whilst for one scenario, forest SOC stocks are predicted to decrease by 0.3 Pg. Different trends are seen in different regions. Climate change will tend to speed decomposition, whereas increases in litter input due to increasing NPP and changing age-class structure will slow the loss of SOC. Increases in forest area could further enhance the total soil carbon stock of European forests. Whilst climate change will be a key driver of change in forest soil carbon, changes in ageclass structure and land-use change are estimated to have greater effects. Key words: Soil organic carbon, Europe, climate change, forest management, land-use change, Rothamsted Carbon model, EFISCEN model, LPJ model
Carbon accumulation in peatlands, southwestern Northwest Territories, Canada
Authors: Robinson Stephen D.
Published: April 2011

Northern peatlands have stored significant quantities of carbon (C) since the early Holocene at rates that vary among peatland types. Pollen concentration dating was used to provide estimates o f true C accumulation and sequestration efficiency in different peatland systems in the discontinuous permafrost zone near Fort Simpson, Northwest Territories, Canada. The catotelm portions of bog, permafrost-affected peat plateau, and Sphagnum-dominated cores were interpreted to conform to Clymo’s (1984) model of C accumulation, while peat deposited under conditions with high water tables (rich fen and collapse fen) did not. The model assumes a consistent surface production, yet production in fens is thought to be highly sensitive to water table changes and may have contributed to poor model fits. Decay rates measured over the past 1200 yr range from 0.0015 to 0.0004 yr-1. True C accumulation rates (range 7.0 in peat plateau to 18.6 g C m-2 yr-1 in bog) and sequestration efficiencies (range 0.24 in peat plateau to 0.67 in poor fen) by 1200 yr BP were low in comparison with other North American sites. Decay rates measured over 1200 yr were significantly greater than that measured over the entire life span of the peatland (0.00033 yr-1), suggesting that a catotelm true C accumulation model incorporating a decreasing rate of decay would be more applicable. Key words: Carbon accumulation, peatlands, permafrost, northern Canada
Modelling soil organic carbon stock change for estimating whole-farm greenhouse gas emissions
Authors: Bolinder M A , VandenBygaart A J , Gregorich E G , Angers D A , Janzen H H
Published: April 2011

Modelling soil organic carbon (SOC) stock changes in agroecosystems can be performed with different approaches depending on objectives and available data. Our objective in this paper is to describe a scheme for developing a dynamic SOC algorithm for calculating net greenhouse gas emissions from Canadian farms as a function of management and local conditions. Our approach is flexible and emphasizes ease of use and the integration of available knowledge. Using this approach, we assessed the performance of several SOC models having two or more compartments for some common agroecosystems in Canada. Analysis of long-term data for conventional management practices at different sites (n = 36) in Canada, including recent model applications in the literature on some of those data, indicated that the results obtained with two-compartment models, such as the Introductory Carbon Balance Model (ICBM) and Modified Woodruff Model (MWM), yielded results comparable to those of a multi-compartment model (CENTURY). The analysis also showed that a model such as ICBM need stuning to be applied to management and conditions across Canada. Two-compartment models programmable in a simple spreadsheet format, though they may not supplant more complex models in allapplications, offer advantages of simplicity and transparency in whole-farm analyses of greenhouse gas emissions. Key words: Virtual Farm, soil organic carbon, soil disturbance, C inputs, Introductory Carbon Balance Model (ICBM), CENTURY, Modified Woodruff Model (MWM).
Towards optimum sampling for regional-scale N2O emission monitoring in Canada
Authors: Pennock D J , Yates T T , Braidek J T
Published: April 2011

There is an increasing need for field monitoring studies of N2O emissions to assess the reliability of process models. Our goal is to review the issues surrounding the design of monitoring and regional upscaling of fieldmeasured N2O emissions for Canadian conditions. Management history creates a range of controlling conditions and emission responses for each land use present in the study region and multiple fields should be sampled within each land use class. The requirement for multiple sample fields necessitates chamber-based sampling designs (ideally in conjunction with site-specific micrometeorological measurements). Uniformly minimum variance unbiased (UMVU) estimators have been recommended for estimation of the mean and variance of the sample distributions, but use of these estimators is limited where zero or negative values occur. Three basic annual emission patterns are observed across a range of N2O studies: background, seasonal, and event + seasonal. The event + seasonal pattern (where short duration, high emission events are superimposed on an underlying seasonal pattern) is common in Canadian agroecosystems. Background and seasonal annual patterns can be effectively captured with biweekly or even triweekly samplings. For the event + seasonal patterns more frequent samplings at periods when emission are believed to be higher (e.g., snow melt or post-fertilization events) are required. Linear interpolation of emissions between the sporadic measurements is the simplest and most reproducible method of temporal interpolation. Spatial extrapolation of the measured emissions is typically done by a measure and multiply approach, where the measured emissions for a given class are multiplied by the area of the class. The methods used to define the soil wetness, land use, and management classes should be clearly defined and consistently applied. The lack of information on the duration and magnitude of event-based emissions and the diurnal pattern of emissions is a major limitation to temporal interpolation. Key words: Greenhouse gas, upscaling, geographical information systems, landscape
Optimizing soil and plant responses to land-applied manure nutrients in the Great Plains of North America
Authors: Schoenau J J , Davis J G
Published: April 2011

Animal manures are recognized as valuable sources of plant nutrients in cropping systems and also play a role in soil improvement through the input of organic matter. Using recent research examples from Saskatchewan and Colorado, this paper covers beneficial management practices for effective recycling of manure nutrients applicable to the Great Plains region of North America. Challenges in using animal manures as fertilizers include low nutrient content per unit weight, variability and availability of nutrient content, and a balance of available nutrients that often does not meet the relative nutrient requirements of the crop. Examples of imbalances that may arise requiring special management considerations include low available N content relative to available P for many solid manures, and low available S relative to N for some liquid manures. Application decisions are best supported by manure and soil analyses, with nutrient balance issues addressed by rate adjustments and the addition of supplemental commercial fertilizer to avoid deficiency or loading of specific nutrients. Placement of manure into the soil by injection or incorporation is desirable in that nutrient losses by volatilization and runoff are reduced and crop recovery is increased. Balancing the rate of nutrient application with crop requirement and removal over time is key to avoiding nutrient loading on soils receiving repeated applications of manure. Key words: Manure management, nutrient cycling, beneficial management practices, Great Plains
The role of composting in recycling manure nutrients
Authors: Larney Francis J , Sullivan Dan M , Buckley Katherine E , Eghball Bahman
Published: April 2011

Recently, composting has been gaining increased attention as an alternative means of handling manure generated by the livestock industry. Composting is not a new technology, it merely controls what is a natural decomposition process. A major advantage of composting is reduced mass, volume and water content compared with fresh manure which in turn reduces transportation requirements. Concomitant benefits include elimination of pathogens, parasites, weed seeds and odour emissions on land application. However, carbon (C) and nitrogen (N) losses and greenhouse gas (GHG) emissions are associated with composting. Nutrients are stabilized during composting which slows their release once soil-applied. Compost also enhances soil physical and biological properties and has a disease suppression effect. Where the supply of manure currently exceeds land availability for application, or in some future scenario, if producers need to comply with stricter manure application rate regulations, composting may be an option to encourage nutrient export from high-loading watersheds to soils that may benefit from nutrient and organic matter inputs. Composting may be seen as a means of maximizing the potential for recycling manure nutrients by soils and crops while protecting surface and groundwater resources from manure-related contamination. Key words: Manure, compost, nutrients, cropping systems, soil quality
Nutrient cycling in the vegetable processing industry: Utilization of potato by-products
Authors: Charmley E. , Nelson D. , Zvomuya F.
Published: April 2011

Potato (Solanum tuberosum) production in Canada and the United States totals approximately 30 × 106 Mg yr-1. Approximately half of this is unsuitable for human consumption. This potato by-product comprises cull potatoes and potato processing waste (PPW). Liquid waste from processing plants can be applied to agricultural land. With strict environmental monitoring and control, crops such as corn (Zea mays L.), vegetables and grass can be used to divert large volumes of liquid waste. Solid waste and culls have traditionally been put in landfills or disposed of on agricultural land as a fertilizer. However these can be diverted from landfill sites or agricultural land and used as a high-quality animal feed, principally in beef feedlots. Research has shown that PPW can replace corn and barley (Hordeum vulgare L.) grain without negative effects on growth of beef cattle or meat quality. Indeed, efficiency of animal growth per unit diet intake is improved. These effects have been observed with diets containing up to 80% PPW. Results to date suggest that PPW is a valuable livestock feed ingredient and has no deleterious effects on beef quality. In areas where PPW is available, feeding to beef cattle represents a viable alternative to other disposal options. Key words: Potato, processing waste, by-product, cattle, land disposal
Soil wetting state and preferential transport of Escherichia coli in clay soils
Authors: Tallon L K , Si B C , Korber D. , Guo X.
Published: April 2011

Transport of Escherichia coli (E. coli) through soil to drinking and recreational water may pose a serious health risk. The objective of this study was to determine how initial preferred soil wetting state influences the preferential transport of E. coli in a clay soil. A strain of E. coli marked with green fluorescent protein (gfp) was gravity-fed-sprinkler-applied as simulated rainfall to three replicates in different wetting states, along with Cl- and adsorptive dye near Plenty, SK. Canada. After 48 h, a 50 × 50 × 50 cm3 block was excavated to determine the transport pathways. Digital image analysis of horizontal sections provided estimates of dye coverage. Escherichia coli were significantly filtered in the top 10 cm of soil with concentration profiles similar to that of Cl-. Ratios of E. coli to Cl- did not show significant differences among treatments (P < 0.05) and indicated that below 10 cm depth, E. coli and Cl- were preferentially transported along the same pathways with no significant difference between plots. Results show that the majority of E. coli and Cl- were filtered when transported through the discontinuous pores of the near-surface matrix and suggest a saturated layer that controlled infiltration into organized root channels, resulting in preferential flow. Key words: Preferential flow, Escherichia coli, wetting state, Vertisol, conducting areas
Dynamics of Escherichia coli in agricultural soils receiving swine manure slurry or liquid municipal biosolids
Authors: Scott Andrew , Conn Ken , Lazarovits George , Topp Edward
Published: April 2011

The fate of two E. coli stains, one that grows in soil receiving swine manure slurry (SMS) (Strain C279) and one that does not (Strain C278) were evaluated in laboratory and field experiments. A sensitive (detection limit 5 cells g soil-1) microplate-format most probable number (MPN) method for enumerating E. coli was developed and validated. In laboratory incubations, there was a general relationship between manure volatile fatty acid (VFA) content and the ability of the SMS to support growth in soil. Strain C279 grew in SMS-amended loam or sandy soil, but not in silt loam soil. Swine manure slurry inoculated with both Strains C278 and C279 was surface or subsurface applied in field microplots. The population of E. coli increased 50-fold within 3 d, and the ratio of Strain C279 to Strain C278 increased as much as 20-fold during the experiment, consistent with the growth of Strain C279 under these circumstances. Liquid municipal biosolids (LMB) obtained from four cities did not support the growth of Strain C279. The dynamics of E. coli populations in soils receiving surface and subsurface (10 cm) applications of SMS were comparable. Key words: Escherichia coli, water quality, liquid municipal biosolids, swine manure slurry
Nitrogen dynamics in soil amended with composted cattle manure
Authors: Helgason Bobbi L , Larney Francis J , Janzen H. Henry , Olson Barry M
Published: April 2011

The amount and pattern of plant-available nitrogen (N) release from composts are variable and not well-defined. We used a 425-d canola (Brassica napus L.) bioassay to follow the release of N from eight composted cattle manures applied to soil at 20 g kg-1. Two stockpiled manures, one inorganic fertilizer and an unamended control were also included for comparison. Eight consecutive 30-d growth cycles were conducted in a controlled environment chamber (20°C) and plant N uptake was measured. Total N uptake was greatest from the N fertilizer and least from the wood-chip bedded manure. Addition of compost increased N uptake by 27–99% compared with that in the control. Nitrogen uptake from compost was directly proportional to its inorganic N content (r2 = 0.98; P < 0.0001) showing that the initial inorganic N content of compost, analyzed prior to its application can be used to predict plant available N. In seven of the eight composts studied, less than 5% of organic N was mineralized over 425 d, suggesting that little of the organic N in compost becomes available in the year of application. Compost is a valuable organic amendment, but co-application of N fertilizer is recommended to supply adequate N and optimize the benefits of compost for crop growth. Key words: Plant-available nitrogen, compost, nitrogen mineralization, beef manure
Soil N and C transformations in two forest clear-cuts during three years after mounding and inverting
Authors: Smolander A. , Heiskanen J.
Published: April 2011

Transformations of nitrogen and carbon in the humus layer were studied in central Finland on two clear-cut forest sites for 3 yr after spot mounding and inverting together with an untreated control. In laboratory-incubation experiments, samples from the humus layer were measured for rates of C mineralization, net N mineralization and net nitrification, and the amounts of C and N in the microbial biomass were determined. Soil solutions were collected for 4 yr with suction lysimeters. Overall, site preparation did not affect the rate of net N mineralization significantly (per kg organic matter). In the first growing season, however, the mean rate of net N mineralization was higher in both site preparation treatments than in the untreated control. At first, net nitrification was negligible in all treatments, but in the second year it increased in both site preparation treatments. On the other site, C mineralization was lowest with inverting, but the amounts of microbial C and N were highest. This indicates a shortage of easily mineralizable C sources in inverted spots. In the soil solution collected below the humus layer, increased concentrations of NO3-N and total N were found in both site-preparation treatments but, during the fourth year, overall concentrations of N had declined. Key words: Boreal forest, clear-cut, N transformations, site preparation, soil solution
Agronomic and environmental soil test phosphorus in manured and non-manured Manitoba soils
Authors: Kumaragamage D. , Akinremi O O , Flaten D. , Heard J.
Published: April 2011

Quantitative relationships between soil test phosphorus (STP) methods are needed to guide P management especially in manured soils with high P. Our objectives were: (i) to compare amounts of P extracted by different methods; (ii) to develop and verify regression equations to convert results among methods; and (iii) to establish environmental P thresholds for different methods, in manured and non-manured soils of Manitoba. We analyzed 214 surface soil samples (0–15 cm), of which 51 had previous manure application. Agronomic STP methods were Olsen (O-P), Mehlich-3 (M3-P), Kelowna-1 (original; K1-P), Kelowna-2 (modified; K2-P), Kelowna-3 (modified; K3-P), Bray-1 (B1-P) and Miller and Axley (MA-P), while environmental STP methods were water extractable (W-P), Ca Cl2 extractable (Ca-P) and iron oxide impregnated filter paper (FeO-P) methods. The different methods extracted different amounts of P, but were linearly correlated. For an O-P range of 0–30 mg kg-1, relationships between O-P and other STP were similar for manured and nonmanured soils, but the relationships diverged at higher O-P levels, indicating that one STP cannot be reliably converted to another using a single equation for manured and non-manured soils at environmentally critical P levels (0–100 mg kg-1 O-P). Suggested environmental soil P threshold ranges, in mg P kg-1, were 88–118 for O-P, 138–184 for K1-P, 108–143 for K2-P, 103–137 for K3-P, 96–128 for B1-P, 84–111 for MA-P, 15–20 for W-P, 5–8 for Ca-P and 85–111 for FeO-P. Key words: Phosphorus, soil test phosphorus, manured soils, non-manured soils, environmental threshold
Modeling mass and nitrogen remaining in litterbags for Canadian forest and climate conditions
Authors: Zhang C. F. , Meng F. -R. , Trofymow J. A. , Arp P. A.
Published: April 2011

A new Forest Litter Decomposition Model (FLDM) is presented to simulate mass, N and carbon/nitrogen ratios (C/N) according to the 1992–1998 leaf litterbag data of the Canadian Intersite Decomposition Experiment (CIDET). This experiment involved 10 litter types, with litterbags placed on the ground of 18 upland and 3 wetland sites across Canada. The calibrated model based on first-order reaction kinetics calculates total mass, N concentration and C/N for each litter type and location using: three compartments (fast, slow, and very slow), four parameters for compartment initialization; three for compartment-based decay; three to assess the climate influence on decay; and one each to determine the rate o f N-mineralization and the final C/N ratio. With FLDM, the initial fast fraction is determined from the initial water-extractable and acid-hydrolyzable or acid-unhydrolyzable portions of the litter; the initial ash content determines the ratio between the slow and very slow fractions. Mean July and January air temperatures, and annual precipitation, determine the climate effect on litter decay. Initial N concentration and the upland-wetland difference determine the N-mineralization coefficient. Model performance was fairly consistent by litter type, location, and year; r2 ranged from 0.83 to 0.97, from 0.64 to 0.92 and from 0.54 to 0.93 for mass remaining, N concentration and C/N, respectively. Key words: Forest litterbags, organic matter decomposition, N concentrations, climate, litter type, CIDET
SWAT-predicted influence of different landscape and cropping system alterations on phosphorus mobility within the Pike River watershed of south-western Québec
Authors: Michaud A. R. , Beaudin I. , Deslandes J. , Bonn F. , Madramootoo C. A.
Published: April 2011

An agreement between the governments of the province of Québec and the State of Vermont calls for a 41% decrease in phosphorus (P) loads reaching Missisquoi Bay, the northern portion of Lake Champlain. The agreement particularly targets the agricultural sector, since 80% of non-point source P inputs to the bay are associated with cultivated lands. In order to identify sustainable cropping practices likely to help meet the target P loads, the SWAT (soil and water assessment tool) model was employed to assess hydrological performance, erosion processes and P mobility on the bay’s principal Québec P contributing tributary, the 630 km2 Pike River watershed. Strong in-watershed spatial clustering of vulnerability to non-point source exports highlights the need for targeted implementation of sustainable agricultural practices and soil conservation works to derive the reduction in P loads. Planting cover crops over the 10% most vulnerable lands would result in roughly a 21% d rop in overall P exports at the watershed outlet, whereas the same 10% randomly distributed over the watershed would only contribute to a 6% drop in P exports. The study of different field-scale management scenarios indicated that achieving the targeted 41% reduction in P exports would require the widespread (half the land devoted to annual crops) implementation of sustainable cropping practices, and the conversion of a specific 10% of the territory to either cover crops or permanent prairie land. Meeting the P target-loads would require additional investments in the protection of floodplains and riparian strips, the targeted construction of runoff-control structures, and the rapid soil incorporation of manures on lands dedicated to annual crops. Key words: Soil and water assessment tool, modelling, sediment, phosphorus, cropping system, scenario, best agricultural management practices
Evaluation of hot KCl extraction as an index of mineralizable N: Ammonium and ultraviolet absorption measurements
Authors: Kowalenko C G
Published: April 2011

Hot KCl extraction was examined as a possible nitrogen (N) soil test. The focus of this study was the influence of the method for determining N in the extracted solution. The study was conducted on a diverse set of Fraser Valley soils of British Columbia, using aerobic incubation as a reference for potential N mineralization rate. The pattern of nitrate and ammonium accumulation over time differed, possibly reflecting differences in organic matter composition, and affecting the interpretation of the results . Results from anaerobic incubation, a simple, alternative method, differed sufficiently from aerobic incubation to warrant caution in using it to estimate mineralization. The MgO steam distillation method was subject to interference in hot KCl extracts; a flow injection system involving room temperature volatilization and diffusion was proposed as a better alternative. Some soils had significant ammonium present before hot KCl extraction, requiring correction. These adjustments, though increasing laboratory requirements, improved the correlation of hot KCl ammonium with aerobically mineralized N. Simple measurements (steam distillation with strong NaOH and ultraviolet absorbance) of organic N extracted by hot KCl were good alternatives for estimating potential N mineralization. Further examination of extraction conditions and measurement variables are required to optimize these methods. Key words: Mineralized soil N, incubation N, soil N test, MgO-steam-distillable N, sodium-hydroxide-distillable N, flow injection analysis, ultraviolet absorbance
Solid/liquid partition coefficients to model trace element critical loads for agricultural soils in Canada
Authors: Sheppard M I , Sheppard S C , Grant C A
Published: April 2011

Canadian consumers are demanding a sustainable agricultural industry as well as products delivered under Best Management Practices (BMPs). Trace element accumulation in soils may influence crop productivity, food quality and ecosystem and human health. Canada’s feed and foodstuff export industry has already faced cases of penalties for high trace element content [cadmium (Cd) in durum wheat]. Thus, it is imperative to be able to estimate the accumulation and potential short- and long-term impacts of trace elements in soil. A national-level Trace Element Indicator (TEI) based on present loadings of trace elements to agricultural land is in progress. An Expert Panel including Canadian, American and Australian experts guided the assembly of a proposed methodology for this TEI. The proposed TEI, described briefly here, is a critical load approach with a single expression of the risk of impact from single or multiple trace elements from multiple sources (manures, biosolids, effluents and fertilizers and natural processes), invoked in a stochastic manner. Two key data requirements are the current background levels of trace elements in soil, and the leachability of these trace elements. A survey of total and soluble concentrations of 54 elements in up to 112 soils was completed. Although preliminary in scope, these represent key soil series in Canada. From this, a database of the solid/liquid partition coefficient, Kd, was computed. These Kd values will be used to characterize the leachability of the trace elements. Key words: Cadmium, copper, zinc, lead, nickel, uranium, metals, Kd, distribution coefficient
Estimates of direct nitrous oxide emissions from Canadian agroecosystems and their uncertainties
Authors: Hutchinson J J , Grant B B , Smith W N , Desjardins R L , Campbell C A , Worth D E , Vergé X P
Published: April 2011

Using a revised Intergovernmental Panel on Climate Change (IPCC) methodology and the process-based model DeNitrification and DeComposition (DNDC), we estimated N2O emissions from agroecosystems in Canada for each census year from 1981 to 2001. Based on the IPCC methodology, direct emissions of N2O ranged from 12.9 to 17.3 with an average of 15.1 Tg CO2 equivalents, while the DNDC model predicted values from 16.0 to 24.3 with an average of 20.8 Tg CO2 equivalents over the same period, and showed a large interannual variation reflecting weather variability. On a provincial basis, emissions estimated by IPCC and DNDC methods were highest in Alberta, Saskatchewan and Ontario, intermediate for Manitoba and Quebec and lowest in British Columbia and the Atlantic provinces. The greatest source of emissions estimated by the IPCC method was from N fertilizer (avg. 6.32 Tg CO2 equiv. in Canada), followed by crop residues (4.24), pasture range and paddocks (PRP) (2.77), and manure (1.65). All sources of emissions, but especially those from fertilizers, increased moderately over time. Monte Carlo Simulation was used to determine the uncertainty associated with the 2001 emission estimates for both IPCC and DNDC methodologies. The simulation generated most likely values of 19.2 and 16.0 Tg CO2 equivalents for IPCC and DNDC, respectively, with uncertainties of 37 and 41%, respectively. Values for the IPCC estimates varied between 28% for PRP and manure and 50% for N fertilizer and crop residues. At the provincial level, uncertainty ranged between 15 and 47% with higher values on the prairies. Sensitivity analyses for IPCC estimates showed crop residues as the most important source of uncertainty followed by synthetic N-fertilizers. Our analysis demonstrated that N2O emissions can be effectively estimated by both the DNDC and IPCC methods and that their uncertainties can be effectively estimated by Monte Carlo Simulation. Key words: Nitrous oxide, IPCC, DNDC model, Uncertainty analysis, Monte Carlo Simulation
Changes to wildlife habitat on agricultural land in Canada, 1981–2001
Authors: Javorek S K , Antonowitsch R. , Callaghan C. , Grant M. , Weins T.
Published: April 2011

Agricultural land in Canada comprises cultivated land, hayland and grazing land with associated riparian areas, wetlands, woodlands, and natural grasslands. Although these agro-ecosystems support many species of Canada’s native fauna, agricultural land use is dynamic, and changes in agricultural practices can have important implications for biodiversity. We report on Agriculture and Agri-Food Canada’s National Agri-environmental Health Analysis and Reporting Program’s assessment of wildlife habitat on farmland in Canada. Habitat use matrices were developed for 493 species of birds, mammals, reptiles and amphibians associated with farm land habitat in Canada. We derived patterns of land use from Statistics Canada’s Census of Agriculture data and applied them at the soil landscape polygon scale. We developed a proportionally weighted Habitat Capacity index to relate habitat use and land use. A 5% decrease in Habitat Capacity occurred on Canada’s agricultural land from 1981 to 2001, associated with an expansion in cropland and a decline in pasture. A regional pattern of small decline in Habitat Capacity is evident in the Prairie Provinces, where dramatic declines in the use of summerfallow had a positive impact on Habitat Capacity. In eastern Canada, greater decreases in Habitat Capacity occurred, associated with an increase in agricultural intensification. Policies and programs designed to sustain biodiversity should not be developed independently of socioeconomic factors or policies favouring agricultural intensification. We recommend a holistic approach to making policy decisions relevant to environmental and economic sustainability in the Canadian agricultural landscape. Key words: Biodiversity, land use change, agroecosystems, wildlife habitat, indicators
Growing season nitrogen dynamics in manured soils in south coastal British Columbia: Implications for a soil nitrate test for silage corn
Authors: Zebarth B. J. , Paul J. W.
Published: April 2011

Spring soil nitrate and ammonium dynamics in south coastal British Columbia soils were examined with respect to the potential to develop a soil nitrate test for silage corn (Zea mays, L.). Soil nitrate and ammonium contents were measured to 90 cm depth in two soils from April to July of two growing seasons. Treatments included a control, spring application of either 300 or 600 kg total N ha−1 as liquid dairy manure, or 200 kg N ha−1 as inorganic fertilizer. Significant amounts of ammonium were present until late May following manure and until mid-June following fertilizer application, requiring simultaneous determination of both nitrate and ammonium concentrations to assess soil inorganic N contents during this period. Most of the changes in soil nitrate over time occurred in the top 30 cm, suggesting that sampling to 30 cm depth would be sufficient in most cases for a soil nitrate test in this region. Most of the increase in soil inorganic N associated with the spring application of manure occurred by 1 June. A soil nitrate test in early to mid-June when the corn is at the six leaf stage appeared to be most suitable for use in south coastal British Columbia to determine if additional fertilizer N is required. A sample taken at this time will measure soil nitrate contents just before the period of rapid corn N uptake, after most of the additional inorganic N associated with spring manure application is already present in the soil as nitrate, and after nitrification of the manure ammonium has occurred.

Key words: N recovery, preplant nitrate test, pre-sidedress soil nitrate test