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Sylvain J.-D.,Universite de Sherbrooke | Michaud A.R.,Institute Of Recherche Et Developpement En Agroenvironnement | Nolin M.C.,Agriculture and Agri Food Canada | Benie G.B.,Universite de Sherbrooke
Digital Soil Assessments and Beyond - Proceedings of the Fifth Global Workshop on Digital Soil Mapping | Year: 2012

This study evaluated quantitative relationships between soil surface reflectance and inherent soil properties to produce digital soil maps supporting precision soil conservation and sustainable water management. Relationships were studied at the laboratory, field and watershed scales. Successive radiometric measurements were taken in the laboratory on 119 undisturbed soil cores following a drying process. Multi-temporal spectral indices were developed from reflectance values quantifying soil moisture, organic matter content and texture. These indices were subsequently validated under uncontrolled moisture conditions on 47 field sites. At the catchment scale (43 km2), the indices were systematically derived from multiple Landsat images acquired under wet and dry conditions. The indices were significantly related to soil moisture (R 2 =0.80) and organic matter content (R 2 =0.89). Prediction models derived from satellite imagery confirmed the potential of spectral indices for mapping soil texture, organic matter content and drainage. © 2012 Taylor & Francis Group.

Rochette P.,Agriculture and Agri Food Canada | Angers D.A.,Agriculture and Agri Food Canada | Chantigny M.H.,Agriculture and Agri Food Canada | Gasser M.-O.,Institute Of Recherche Et Developpement En Agroenvironnement | And 3 more authors.
Canadian Journal of Soil Science | Year: 2013

Subsurface banding of urea can result in large ammonia (NH3) emissions following a local increase in soil ammonium (NH4 +) concentration and pH. We conducted a field experiment to determine how application rates of subsurface banded urea impact NH3 volatilization. Urea was banded at a 5 cm depth to a silty loam soil (pH = 5.5) at rates of 0, 6.1, 9.2, 13.3 and 15.3 g N m -1. Ammonia volatilization (wind tunnels), and soil NH4 + concentration and pH (0-10 cm) were monitored for 25 d following urea application. Volatilization losses increased exponentially with urea application rate to 11.6% of applied N for the highest urea rate, indicating that as more urea N was added to the soil a larger fraction was lost as NH3. Cumulative NH3-N emissions were closely related (R2≥ 0.85) to maximum increases in soil NH4 + concentration and pH, and their combined influence likely contributed to the nonlinearity of the volatilization response to urea application rate. However, the rapid increase in NH3 losses when soil pH rose above 7 suggests that soil pH was the main factor explaining the nonlinear response of NH3 volatilization. When compared with previous studies, our results suggest that the response of NH3 volatilization losses to urea application rate in acidic soils are controlled by similar factors whether urea is broadcasted at the soil surface or subsurface banded.

Chantigny M.H.,Agriculture and Agri Food Canada | MacDonald J.D.,Environment Canada | Angers D.A.,Agriculture and Agri Food Canada | Rochette P.,Agriculture and Agri Food Canada | And 2 more authors.
Canadian Journal of Soil Science | Year: 2013

Grassland soils accumulate N, which could be lost following land-use change. Adjacent grassland sites, with and without liquid swine manure applied annually for 28 yr, were subdivided and left undisturbed (Control), or killed by herbicides with and without full inversion tillage (FIT) in the autumn or spring. We monitored hot-water extractable organic N (HWEON), and mineral N forms in KCl extractions and soil solutions (tension lysimeters) for 1 yr. Mean soil mineral N increased by 1 to 2.8 g m -2 in the weeks following herbicide kill and FIT of the unmanured soils, and by 2.6 to 3.0 g m -2 in the manured soil. These increases corresponded to declines in soil HWEON (-0.4 to - 1.9 g m -2 unmanured site; -2.4 to -4.9 g m -2 manured site), suggesting that HWEON comprised N that is rapidly mineralized following grassland termination. More than 80% of N mineralized in the weeks following termination accumulated as NH4 in the unmanured soils, compared with >70% as NO3 in the manured soils. As a result, more mineral N (mainly NO3) was found in the soil solution of manured soils. Manured grassland soils may represent a high risk of N loss following termination with herbicide in combination with FIT in the autumn, because of the rapid nitrification of mineralized N. For spring FIT, however, the rapid mineralization of soil N may represent a substantial nutrient source to the following crop.

Rochette P.,Agriculture and Agri Food Canada | Angers D.A.,Agriculture and Agri Food Canada | Chantigny M.H.,Agriculture and Agri Food Canada | Gasser M.-O.,Institute Of Recherche Et Developpement En Agroenvironnement | And 3 more authors.
Journal of Environmental Quality | Year: 2013

Incorporation of urea decreases ammonia (NH3) volatilization, but field measurements are needed to better quantify the impact of placement depth. In this study, we measured the volatilization losses after banding of urea at depths of 0, 2.5, 5, 7.5, and 10 cm in a slightly acidic (pH 6) silt loam soil using wind tunnels. Mineral nitrogen (N) concentration and pH were measured in the top 2 cm of soil to determine the extent of urea N migration and the influence of placement depth on the availability of ammoniacal N for volatilization near the soil surface. Ammonia volatilization losses were 50% of applied N when urea was banded at the surface, and incorporation of the band decreased emissions by an average of 7% cm-1 (14% cm-1 when expressed as a percentage of losses after surface banding). Incorporating urea at depths >7.5 cm therefore resulted in negligible NH3 emissions and maximum N retention. Cumulative losses increased exponentially with increasing maximum NH4 +-N and pH values measured in the surface soil during the experiment. However, temporal variations in these soil properties were poorly related to the temporal variations in NH3 emission rates, likely as a result of interactions with other factors (e.g., water content and NH4 +-N adsorption) on, and fixation by, soil particles. Laboratory and field volatilization data from the literature were summarized and used to determine a relationship between NH3 losses and depth of urea incorporation. When emissions were expressed as a percentage of losses for a surface application, the mean reduction after urea incorporation was approximately 12.5% cm-1. Although we agree that the efficiency of urea incorporation to reduce NH3 losses varies depending on several soil properties, management practices, and climatic conditions, we propose that this value represents an estimate of the mean impact of incorporation depth that could be used when site-specific information is unavailable. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Cote D.,Institute Of Recherche Et Developpement En Agroenvironnement
Nutrient Cycling in Agroecosystems | Year: 2010

Liquid hog manure (LHM) is a valuable source of nutrients for farm production. Long-term experimental plots that had received LHM applications of 0, 50, and 100 m3 ha-1 annually for 20 years were analyzed for total soil C, N and P storage. Applications increased total soil N and P by 1,200 kg N ha-1 and 850 kg P ha-1 at 100 m-3 LHM year-1, compared to the control treatment. However, C storage did not increase with LHM rates and was lower in the 50 m3 ha-1 LHM treatment (86 Mg C ha-1) than in the 0 or 100 m3 ha-1 treatments (100 Mg C ha-1). In addition to the limited quantities and high decomposability of the C supplied by LHM, it is hypothesized that LHM stimulated the mineralization of both native soil C and fresh root-derived material. This priming effect was particularly apparent in deeper soil horizons where the decomposability of native C may be limited by the supply of fresh C. This study indicates that while LHM can be a significant source of crop nutrients, it has limited capacity for maintaining or increasing soil C. © 2009 Springer Science+Business Media B.V.

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