Cutforth, H. W., Angadi, S. V., McConkey, B. G., Miller, P. R., Ulrich, D., Gulden, R., Volkmar, K. M., Entz, M. H. and Brandt, S. A. 2013. Comparing rooting characteristics and soil water withdrawal patterns of wheat with alternative oilseed and pulse crops grown in the semiarid Canadian prairie. Can. J. Soil Sci. 93: 147-160. To improve sustainability and increase economic returns, producers in the semiarid Canadian prairie are diversifying their cropping systems to include alternative crops such as pulses and oilseeds in rotation with wheat. Producers must adopt crops and cropping systems that use water most efficiently. We compared the root systems and water withdrawal patterns for three pulse crops (leguminous grain crops) [chickpea (Cicer arietinum L.), pea (Pisum sativum L.) and lentil (Lens culinaris Medik. L.)] and three oilseed crops [canola (Brassicanapus L. and Brassica rapa L.) and mustard (Brassica juncea L.)] with one cereal crop [wheat (Triticum aestivum L.)] under well-watered, rain-fed, imposed drought water regimes during 1996-1998. Wheat withdrew the most water, whereas pulses withdrew the least amount of water from the soil profile. Pulses withdrew substantially less water than oilseeds and wheat below about the 80-cm depth, whereas oilseeds withdrew less water than wheat from the upper regions of the soil profile, thus increasing soil water available to the following crops. Therefore, producers can increase the overall efficiency of a crop rotation by growing deeper rooting crops, such as wheat and canola, following pulses, and by growing crops, such as wheat, that will use the increased soil water reserves following canola.

Baugé, S. M. Y., Lavkulich, L. M. and Schreier, H. E. 2013. Serpentine affected soils and the formation of magnesium phosphates (struvite). Can. J. Soil Sci. 93: 161-172. The Sumas River watershed, located in the intensive agricultural region of the Lower Fraser Valley of British Columbia (Canada), contains serpentine asbestos from a natural landslide. Serpentinic soils have a high Mg to Ca ratio that can affect soil fertility, including soil-solution P relations. The objectives of the study were: (i) to evaluate some common methods of estimating plant available phosphorus in the surface horizons of the serpentine-affected soils and those receiving large quantities of livestock manure, and (ii) to determine if there is evidence for the formation of soluble Mg phosphates, e.g., struvite, a meta-stable P phase in these soils. Seven soil nutrient extractants were used to determine major and minor elemental concentrations. Acid ammonium oxalate, 1 M HCl and Bray P1 extractions were most effective for measuring available phosphorus in these soils. Manure and fertilizer applications appear to favor the formation of Mg-phosphates, and are considered to be more soluble in terms of phosphorus than either calcium-phosphates or aluminum/iron-phosphates. X-ray diffraction, scanning electron microscopy and nuclear magnetic resonance examinations gave positive evidence for the presence of struvite in the soils.

Woods, S. A., Dyck, M. F. and Kachanoski, R. G. 2013. Spatial and temporal variability of soil horizons and long-term solute transport under semi-arid conditions. Can. J. Soil Sci. 93: 173-191. Characterizing the spatial and temporal variability of deep drainage is required for quantifying risks to groundwater resources associated with chemicals released into the soil. A variety of approaches are available to characterize the spatial variability of deep drainage, including complex, spatially explicit hydrological models or simpler, distributed soil water balance models. There is no clear understanding which approach is most appropriate for a given landscape. In this paper we compare the spatial distribution of an applied chloride tracer to pedogenic nitrate and sulphate salts, subject to transport in the soil over decadal to millennial time scales, to characterize the relative spatial and temporal differences in deep drainage at a site in southern Saskatchewan. Comparison of the spatial distribution of the salts with differing soil residence times showed that the soil water balance and deep drainage fluxes have changed significantly over time in some parts of the landscape because of infilling of surface depressions as indicated by the presence of buried A horizons. At larger scales, the distribution of the salts showed very little correspondence to the spatial distribution and thicknesses of soil horizons (often used to infer spatial variability in soil water balance), but was more consistent with the scale of the surface topography. Thus it was concluded that spatial and temporal changes in surface topography (i.e., catchment area) were the primary factors responsible for the observed transport of the salts. We propose that this site is representative of the cold, semi-arid prairies and that these conclusions likely apply to this region.

Zhao, Z., Ashraf, M. I., Keys, K. S. and Meng, F-R. 2013. Prediction of soil nutrient regime based on a model of DEM-generated clay content for the province of Nova Scotia, Canada. Can. J. Soil Sci. 93: 193-203. Soil nutrient regime (SNR) maps are widely required by ecological studies as well as forest growth and yield assessment. Traditionally, SNR is assessed in the field using vegetation indicators, topography and soil properties. However, field assessments are expensive, time consuming and not suitable for producing high-resolution SNR maps over a large area. The objective of this research was to develop a new model for producing high-resolution SNR maps over a large area (in this case, the province of Nova Scotia). The model used 10-m resolution clay content maps generated from digital elevation model data to capture local SNR variability (associated with topography) along with coarse-resolution soil maps to capture regional SNR variability (associated with differences in landform/parent material types). Field data from 1385 forest plots were used to calibrate the model and another 125 independent plots were used for model validation. Results showed field-identified SNRs were positively correlated with predicted clay content, with some variability associated with different landform/parent material types. Accuracy assessment showed that 63.7% of model-predicted SNRs were the same as field assessment, with 96.5% within ±1 class compared with field-identified SNRs. The predicted high-resolution SNR map was also able to capture the influence of topography on SNR which was not possible when predicting SNR from coarse-resolution soil maps alone.

Peralta, N. R., Costa, J. L., Balzarini, M. and Angelini, H. 2013. Delineation of management zones with measurements of soil apparent electrical conductivity in the southeastern pampas. Can. J. Soil Sci. 93: 205-218. Site-specific management demands the identification of subfield regions with homogeneous characteristics (management zones). However, determination of subfield areas is difficult because of complex correlations and spatial variability of soil properties responsible for variations in crop yields within the field. We evaluated whether apparent electrical conductivity (EC_a) is a potential estimator of soil properties, and a tool for the delimitation of homogeneous zones. EC_a mapping of a total of 647 ha was performed in four sites of Argentinean pampas, with two fields per site composed of several soil series. Soil properties and EC_a were analyzed using principal components (PC)-stepwise regression and ANOVA. The PC-stepwise regression showed that clay, soil organic matter (SOM), cation exchange capacity (CEC) and soil gravimetric water content (_g) are key loading factors, for explaining the EC_a (R²≥0.50). In contrast, silt, sand, extract electrical conductivity (EC_ext), pH values and-N content were not able to explain the EC_a. The ANOVA showed that EC_a measurements successfully delimited three homogeneous soil zones associated with spatial distribution of clay, soil moisture, CEC, SOM content and pH. These results suggest that field-scale EC_a maps have the potential to design sampling zones to implement site-specific management strategies.

Li, X., Ziadi, N., Bélanger, G., Yuan, W., Liang, S., Xu, H. and Cai, Z. 2013. Wheat grain Cd concentration and uptake as affected by timing of fertilizer N application. Can. J. Soil Sci. 93: 219-222. The effect of a single N application (120 kg ha^-1) at seeding on wheat (Triticum aestivum L.) grain Cd concentration and uptake was compared with an equally split N application (seeding and the stem elongation stage) in a field experiment at 12 site-years. Averaged across all site-years, the single N application tended to reduce wheat grain Cd concentration (58 vs. 68 µg kg^-1 DM) and uptake (151 vs. 191 mg ha^-1) compared with the split application. The Cd concentrations, however, never exceeded the maximum acceptable level for Cd in wheat grain. A single N application at seeding might reduce the risk of high grain Cd concentration in spring wheat.

Karamanos, R. E., Harapiak, J. T. and Flore N. A. 2013. Sulphur application does not improve wheat yield and protein concentration. Can. J. Soil Sci. 93: 223-228. Grain protein plays an important role in the milling and baking quality of wheat (Triticum aestivum). The question is whether application of sulphur, an important constituent of proteins and amino acids, impacts wheat grain protein concentration. A 3-yr 10-site experiment was set up to determine if of sulphur (S) fertilization (0 and 25 kg S ha^-1) affects Canada west red spring (CWRS) and Durum grain yield and protein levels, when combined with various rates of nitrogen (N) fertilizer (0, 40, 60, 80 and 100 kg N ha^-1). Soils at the 10 sites varied from S deficient to S sufficient, based on criteria in western Canada. Application of 25 kg S ha^-1 resulted in no yield or grain protein concentration increases, regardless of the level of N fertilizer applied or the level of soil “available” S (0-30 cm). However, high N fertilizer rates (80 and 100 kg N ha^-1) plus S fertilization improved yield and protein concentration when growing season (May, June, July) precipitation was favourable for CWRS and Durum wheat. In conclusion, we suggest that indiscriminate application of S fertilizer will not increase protein concentration for CWRS and Durum wheat grain.

Chantigny, M. H., MacDonald, J. D., Angers, D. A., Rochette, P., Royer, I. and Gasser, M.-O. 2013. Soil nitrogen dynamics following herbicide kill and tillage of manured and unmanured grasslands. Can. J. Soil Sci. 93: 229-237. 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.

Engel, R., Jones, C. and Wallander, R. 2013. Ammonia volatilization losses were small after mowing field peas in dry conditions. Can. J. Soil Sci. 93: 239-242. Ammonia losses following termination of peas (Pisum sativum L.) by mowing were measured using a micrometeorological mass-balance approach. Field trials were conducted during two seasons in a semiarid climate. Plant N in the above ground biomass was 105 and 79 kg N ha^-1 in 2011 and 2012, respectively. Vertical NH₃ flux estimates were nominal (0.3 to 1.7 g N ha^-1 h^-1) in the 2 wk following mowing. Cumulative NH₃ loss represented 0.3 to 0.5% of the N in plant biomass, indicating that N fertility was not diminished by NH₃ volatilization in this dry climate.

Qian, B., De Jong, R., Gameda, S., Huffman, T., Neilsen, D., Desjardins, R., Wang, H. and McConkey, B. 2013. Impact of climate change scenarios on Canadian agroclimatic indices. Can. J. Soil Sci. 93: 243-259. The Canadian agricultural sector is facing the impacts of climate change. Future scenarios of agroclimatic change provide information for assessing climate change impacts and developing adaptation strategies. The goal of this study was to derive and compare agroclimatic indices based on current and projected future climate scenarios and to discuss the potential implications of climate change impacts on agricultural production and adaptation strategies in Canada. Downscaled daily climate scenarios, including maximum and minimum temperatures and precipitation for a future time period, 2040-2069, were generated using the stochastic weather generator AAFC-WG for Canadian agricultural regions on a 0.5°×0.5° grid. Multiple climate scenarios were developed, based on the results of climate change simulations conducted using two global climate models - CGCM3 and HadGEM1 - forced by IPCC SRES greenhouse gas (GHG) emission scenarios A2, A1B and B1, as well as two regional climate models forced by the A2 emission scenario. The agroclimatic indices that estimate growing season start, end and length, as well as heat accumulations and moisture conditions during the growing season for three types of field crops, cool season, warm season and over-wintering crops, were used to represent agroclimatic conditions. Compared with the baseline period 1961-1990, growing seasons were projected to start earlier, on average 13 d earlier for cool season and over-wintering crops and 11 d earlier for warm season crops. The end of the growing season was projected on average to be 10 and 13 d later for over-wintering and warm season crops, respectively, but 11 d earlier for cool season crops because of the projected high summer temperatures. Two indices quantifying the heat accumulation during the growing season, effective growing degree days (EGDD) and crop heat units (CHU) indicated a notable increase in heat accumulation: on average, EGDD increased by 15, 55 and 34% for cool season, warm season and over-wintering crops, respectively. The magnitudes of the projected changes were highly dependent on the climate models, as well as on the GHG emission scenarios. Some contradictory projections were observed for moisture conditions based on precipitation deficit accumulated over the growing season. This confirmed that the uncertainties in climate projections were large, especially those related to precipitation, and such uncertainties should be taken into account in decision making when adaptation strategies are developed. Nevertheless, the projected changes in indices related to temperature were fairly consistent.

Rochette, P., Angers, D. A., Chantigny, M. H., Gasser, M.-O., MacDonald, J. D., Pelster, D. E. and Bertrand, N. 2013. NH₃volatilization, soilconcentration and soil pH following subsurface banding of urea at increasing rates. Can. J. Soil Sci. 93: 261-268. Subsurface banding of urea can result in large ammonia (NH₃) emissions following a local increase in soil ammonium () 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 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 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.