R. 2012. Controlled release fertilizer product effects on potato crop response and nitrous oxide emissions under rain-fed production on a medium-textured soil. Can. J. Soil Sci. 92: 759Á769. Controlled release fertilizers and split fertilizer N applications are expected to provide plant-available nitrogen (N) in synchrony with crop requirements, which should mitigate nitrous oxide (N 2 O) emissions from agricultural soils. This study compared a polymer coated urea (PCU) controlled release N fertilizer (Environmentally Smart Nitrogen), split fertilizer N application and conventional fertilizer N management on the crop response and growing season N 2 O emissions from rain-fed potato (Solanum tuberosum L.) production on a medium-textured soil in Atlantic Canada from 2008 to 2010. Fertilizer were applied at the recommended rate (193 kg N ha (1 ) and treatments included the PCU product banded at planting, conventional fertilizer in a split application (60% as diammonium phosphate plus ammonium nitrate at planting plus 40% as ammonium nitrate at final hilling), conventional fertilizer (diammonium phosphate plus ammonium nitrate) banded at planting, and an unfertilized control. Within each year, cumulative growing season N 2 O emissions were closely related to soil nitrate availability as measured by nitrate exposure (sum of daily nitrate concentration in the surface soil). Split N application had no effect on crop response, and significantly reduced nitrate exposure, but did not reduce N 2 O emissions. With the PCU, there was evidence of increased plant N availability and greater N 2 O emissions. In situations where the risk of nitrate leaching is limited, substitution of a PCU product for conventional fertilizer at the same N application rate will not necessarily reduce growing season N 2 O emissions and may in some cases increase the risk of N 2 O emissions. Further research is required to determine if lowering N rates with PCU products will be effective agronomically and environmentally. . et Dowbenko, R. 2012. Incidence des engrais a`libe´ration lente sur le rendement de la pomme de terre et sur les e´missions d'oxyde nitreux dans les sols non irrigue´s de granulome´trie moyenne. Can. J. Soil Sci. 92: 759Á769. L'application d'engrais a`libe´ration lente ou leur application fractionne´e devrait procurer aux plantes suffisamment d'azote (N) assimilable, en synchronisme avec les besoins de la culture, ce qui devrait re´duire les e´missions d'oxyde nitreux (N 2 O) des sols agricoles. La pre´sente e´tude compare l'incidence des engrais N a`libe´ration lente ab ase d'ure´e enrobe´e de polyme`re (PCU), aussi appele´s azote e´cologique, de l'application fractionne´e d'engrais N et des pratiques courantes d'amendement sur la re´action de la culture et sur les e´missions saisonnie`res de N 2 O pour la pomme de terre (Solanum tuberosum L.) cultive´e sans irrigation sur un sol de texture moyenne, dans les provinces de l'Atlantique, de 2008 a`2010. L'engrais a e´te´applique´au taux recommande´(193 kg de N par hectare) et les t...

. 2015. Predicting soil nitrogen supply from soil properties. Can. J. Soil Sci. 95: 63Á75. Prediction functions based on simple kinetic models can be used to estimate soil N mineralization as an aid to improved fertilizer N management, but require long-term incubations to obtain the necessary parameters. Therefore, the objective of this study was to examine the feasibility of predicting the mineralizable N parameters necessary to implement prediction functions and in addition to verify their efficiency in modeling soil N supply (SNS) over a growing season. To implement a prediction function based on a first-order (F) kinetic model, a regression equation was developed using a data base of 92 soils, which accounted for 65% of the variance in potentially mineralizable N (N 0 ) using soil total N (STN) and Pool I, a labile mineralizable N pool. However, the F prediction function did not provide satisfactory prediction (R 2 00.17Á0.18) of SNS when compared with a field-based measure of SNS (PASNS) if values of N 0 were predicted from the regression equation. We also examined a two-pool zero-plus first-order (ZF) prediction function. A regression model was developed including soil organic C and Pool I and explained 66% of the variance in k S , the rate constant of the zero-order pool. In addition, a regression equation was developed which explained 86% of the variance in the size of the first-order pool, N L , from Pool I. The ZF prediction function provided satisfactory prediction of SNS (R 2 00.41Á0.49) using both measured and predicted values of k S and N L . This study demonstrated a simple prediction function can be used to estimate SNS over a growing season where the mineralizable N parameters are predicted from simple soil properties using regression equations.Key words: Arable crops, kinetic equations, mineralizable N pools, prediction, regression models Dessureault-Rompre´, J., Zebarth, B. J., Burton, D. L. et Georgallas, A. 2015. Pre´vision des re´serves d'azote a`partir des proprie´te´s du sol. Can. J. Soil Sci. 95: 63Á75. On peut recourir aux fonctions de pre´vision reposant sur de simples mode`les cine´tiques pour estimer la mine´ralisation du N dans le sol et faciliter la gestion des amendements azote´s, mais obtenir les parame`tres requis pour cela ne´cessite de longues incubations. L'e´tude devait e´tablir s'il est possible de pre´voir les parame`tres du N mine´ralisable essentiels a`l'application des fonctions de pre´vision, puis d'en ve´rifier l'efficacite´en mode´lisant les re´serves d'azote du sol au cours d'une pe´riode ve´ge´tative. Pour appliquer une fonction de pre´vision qui reposait sur un mode`le cine´tique du premier degre´(F), les auteurs ont e´labore´une e´quation de re´gression en recourant a`une base de donne´es sur 92 sols qui expliquait 65 % de la variance du N susceptible d'eˆtre mine´ralise´(N 0 ) a`partir de la concentration totale de N dans le sol et du bassin I, une re´serve de N mine´ralisable labile. La fonction F ne permet pas de pre´voir de fac¸on satisfaisante (R 2 0 0.17Á0....

Wile, A., Burton, D. L., Sharifi, M., Lynch, D., Main, M. and Papadopoulos, Y. A. 2014. Effect of nitrogen fertilizer application rate on yield, methane and nitrous oxide emissions from switchgrass (Panicum virgatum L.) and reed canarygrass (Phalaris arundinacea L.). Can. J. Soil Sci. 94: 129–137. This 2-yr (2008–2009) study conducted in Truro, Nova Scotia, measured plant biomass production (yield and ash content) and greenhouse gas emissions (methane and nitrous oxide), from the bioenergy crops switchgrass (SG; Panicum virgatum L.) and reed canarygrass (RCG; Phalaris arundinacea L.) receiving spring application of nitrogen fertilizer at 0, 40 and 120 kg N ha−1. In both years, crop yields were unresponsive to N fertilizer. In 2008, SG average yields were greater than RCG producing 7.0 vs. 4.6 Mg ha−1, respectively, while ash content was significantly greater for RCG in both years. Cumulative seasonal (May–November) N2O emissions were<1 kg N2O-N ha−1 in 2008 and<0.2 kg N2O-N ha−1 in 2009 with crop (SG>RCG) and N fertilizer (N120>N40=N0) effects found in 2008 only. Nitrate exposure was greater for SG in 2008 only, but responded to N fertilization in both years (N120>N0). These crops were net sinks for methane and the magnitude of the sink was not influenced by crop type, N fertilization or year. Despite lower yields, the greenhouse gas intensity calculated for RCG (−2 to 20 kg CO2e t−1 biomass) was lower than for SG (8 – 60 kg CO2e t−1 biomass) as a result of lower N2O emissions.

Snowdon, E., Zebarth, B. J., Burton, D. L., Goyer, C. and Rochette, P. 2013. Growing season N2O emissions from two-year potato rotations in a humid environment in New Brunswick, Canada. Can. J. Soil Sci. 93: 279–294. Few studies have examined the effects of crop rotation on N2O emissions. This study quantified N2O emissions from seven 2-yr potato rotations over a 3-yr period, 2008–2010, where the potato phase was present in 2008 and 2010. In addition, the potential to predict variation in cumulative growing season N2O emissions was examined using indices of nitrate availability [nitrate exposure (NE), a time integrated measure of soil nitrate concentrations in the surface soil], carbon availability (cumulative growing season CO2 emissions) and aeration [time-weighted average water-filled pore space (WFPS)]. In the potato phase of the rotations, even for treatments receiving the same fertilizer N rate (193 kg N ha−1), a wide range in cumulative growing season N2O emissions was measured in both 2008 and 2010 (0.39–1.49 and 0.81–2.03 kg N ha−1, respectively). The NE explained 52 and 70% of the variation in growing season N2O emissions under potato production in 2008 and 2010, respectively. Carbon availability also had a significant effect on N2O emissions, as indicated by increased N2O emissions in rotations where residues of the preceding crop resulted in increased CO2 emissions early in the growing season. A large proportion (67%) of the variation in cumulative N2O emissions among rotation crops was also explained by NE. Choice of rotation crop resulted in an almost twofold difference (0.9–1.7 kg N ha−1) in N2O emissions over the 2-yr rotation cycle. Greater N2O emissions over the 2-yr rotation cycle were measured for rotation crops of soybean, Italian ryegrass, red clover and potato than for rotation crops of corn, canola and barley. However, the fertilizer N management in both the potato and rotation crop phases may be as or more important than the choice of rotation crop in influencing the risk of N2O emissions.