Harvesting corn (Zea mays L.) stover for production of biofuels, industrial sugars, bioproducts, and livestock bedding is increasing rapidly, but little is known of the impacts of stover removal on soil-borne greenhouse gas (GHG) emissions. This study evaluated the impacts of removing surface corn stover (0, 25, 50, 75, 100 wt. % removal) on carbon dioxide (CO2) and nitrous oxide (N2O) emissions from a sandy loam soil cropped to monoculture corn using conventional moldboard plow tillage (CT) and no-tillage (NT). Stover removal systematically decreased CO2 emissions from CT, whereas stover removal had little effect on CO2 emissions from NT. In particular, the CT 0% stover removal treatment produced 47% greater CO2 emissions (5.75 Mg CO2-C ha(-1)) than the CT 100% removal (3.91 Mg CO2-C ha(-1)) treatment. Stover removal increased N2O emissions from both tillage treatments, producing up to a 75% increase under CT (2.79 kg N ha(-1) at 0% removal; 4.87 kg N ha(-1) at 100% removal) and up to a 95% increase under NT (1.75 kg N ha(-1) at 0% removal; 3.41 kg N ha(-1) at 100% removal). Cumulative nitrate exposure increased in comparable patterns to N2O emissions when stover residues were removed. There was a trade-off in GHG emissions resulting from stover removal under CT, whereby increasing stover removal reduced CO2 emissions but increased N2O emissions. In contrast, stover removal did not affect CO2 emissions under NT but it increased N2O emissions especially at the 100% removal rates.

Nitrogen loss through ammonia volatilization is an environmental and economic concern. When acid traps are used with wind tunnels to measure ammonia volatilization, loss of solution volume is observed. As the loss mechanism affects volatilization estimates, a field study was conducted to determine if solution loss from acid traps was due to either selective loss of water through evaporation, loss of bulk solution, or a combination. Two methods for calculating air flow volume through the acid traps were also examined. Solution losses from acid traps averaged 40 mL d(-1) (+/- 9.2 mL) from an initial 100 mL, and ammonium concentration increased in close accordance with the dilution - concentration relationship for aqueous solutions. Hence, solution loss was due to evaporation, with virtually no ammonium loss, confirming that the flux calculations using corrected acid trap volumes are required. Failure to correct for the reduced volumes resulted in 9%-224% overestimation of ammonium concentrations. Air flow volumes through acid traps were underestimated by 18.5% when initial and final air flow rates were used compared with continuous cumulative flow measurements. Using cumulative flows and accounting for evaporation loss from acid traps help ensure that treatment differences are not masked by the inherent variability in field-based measurements.

Core Ideas Streaming urea ammonium nitrate resulted in 11% lower corn yields compared to injected urea ammonium nitrate. Ammonia volatilization (NH 3 ) begins immediately after application for streaming urea ammonium nitrate. In 2015–2016, NH 3 loss was 3.6 fold greater for streaming urea ammonium nitrate compared to injected urea ammonium nitrate. Urease and nitrification inhibitors did not increase corn yields with streaming urea ammonium nitrate. Streaming urea ammonium nitrate with a urease inhibitor increased N 2 O emissions by 18.7%. Surface streaming urea ammonium nitrate (UAN) into corn ( Zea mays L.) at side‐dress (v4–v6) or later in the season (v12–v14) is an emerging N fertilizer application method as it is rapid, reduces soil disturbance, and allows for flexible application times. In 2013 and 2014, side‐dress N application (130 kg N ha −1 ) using three streaming UAN sources was evaluated for their ability to maintain grain yield, reduce ammonia (NH 3 ) volatilization, and mitigate nitrous oxide (N 2 O) emissions. The products included streaming of urea ammonium nitrate (StrUAN), urea ammonium nitrate with a urease inhibitor (StrUAN‐UI), urea ammonium nitrate with urease inhibitor plus nitrification inhibitor (StrUAN‐UI+NI), and a control (no N). The efficacy of streaming relative to traditional shallow‐injected urea ammonium nitrate (InjUAN) was also assessed. Delayed NH 3 sampling related to wind‐tunnel installation in 2013 and 2014 led to additional NH 3 measurements in 2015 and 2016. Average yields from StrUAN were 11% lower relative to InjUAN. The use of inhibitors did not improve yields relative to StrUAN. Ammonia volatilization was not significantly different between StrUAN and InjUAN losing 14 and 20% of applied N (2‐yr average), respectively. However in 2015 and 2016, NH 3 volatilization from StrUAN was 3.6‐fold greater than InjUAN when measurements were started immediately after application. Hence lower yields in 2013 and 2014 from StrUAN likely reflect N loss to rapid volatilization during or shortly after application. The StrUAN‐UI treatment increased 2‐yr average N 2 O emissions by 17.3 to 18.7% relative to StrUAN or StrUAN‐UI+NI. For humid‐temperate clay loam soil, UAN streaming with/without inhibitors was not effective for maintaining yields or reducing NH 3 volatilization.

Nitrogen (N) leaching from soil into surface and ground waters is a concern in humid areas of Canada. As a result, N management protocols, including the Ontario N Index, are widely used to identify N leaching risk, although field assessment remains limited. Nitrogen fertilizer and chloride (Cl) tracer were fall-applied to five agricultural soils in Ontario with different textures and hydrologic soil groups (HSG) to assess the Ontario N Index and characterize inorganic N movement over 1 yr. The treatments included three N rates (0, 100, and 200 kg N ha−1) plus Cl tracer and 200 kg N ha−1 rate without Cl. After spring thaw, N loss from the crop root zone (top 60 cm) ranged from 68% for Brookston clay loam to 99% for Harrow sandy loam. A strong linear relationship between apparent N recovery and apparent Cl recovery indicated that N loss from the root zone occurred primarily by downward leaching. Leaching was controlled by the minimum measured saturated hydraulic conductivity (Ksat), and good estimates of N leaching were obtained using a quasi-theoretical relationship between N loss and Ksat. We concluded that Ontario N Index estimates of N leaching risk might be improved by including site-specific measurements of Ksat.

Drury, C. F., Reynolds, W. D., Tan, C. S., McLaughlin, N. B., Yang, X. M., Calder, W., Oloya, T. O. and Yang, J. Y. 2014. Impacts of 49–51 years of years of fertilization and crop rotation on growing season nitrous oxide emissions, nitrogen uptake and corn yields. Can. J. Soil Sci. 94: 421–433. A field study was established in 1959 to evaluate the effects of fertilization and crop rotation on crop yields, soil and environmental quality on a Brookston clay loam. There were two fertilizer treatments (fertilized and not-fertilized) and six cropping treatments including continuous corn (CC), continuous Kentucky bluegrass sod and a 4-yr rotation of corn–oat–alfalfa–alfalfa with each phase present each year. We measured N2O emissions, inorganic N and plant N uptake over three growing seasons (2007–2009) in the corn phase. Nitrous oxide emissions varied over the 3 yr as a result of the seasonal variation in precipitation quantity, intensity and timing and differences in crop growth and N uptake. Fertilized CC lost, on average, 7.36 kg N ha−1 by N2O emissions, whereas the not-fertilized CC lost only 0.51 kg N ha−1. Fertilized rotation corn (RC) lost 6.46 kg N ha−1, which was 12% lower than fertilized CC. The not-fertilized RC, on the other hand, emitted about half as much N2O (2.95 kg N ha−1) as the fertilized RC. Fertilized RC had corn grain yields that averaged 10.0 t ha−1 over the 3 yr followed by fertilized CC at 5.48 t ha−1. Not-fertilized RC corn had yields that were 61% lower (3.93 t ha−1) than fertilized RC, whereas the not-fertilized CC had yields that were 75% lower (1.39 t ha−1) than fertilized CC. Nitrous oxide emissions were found to be dramatically affected by long-term management practices and crop rotation had lower emissions in the corn phase of the rotation even though the N input from fertilizer addition and legume N fixation was greater. These N2O emission and yield results were due to both factors that are traditionally used to describe these processes as well as long-term soil quality factors, which were created by the long-term management (i.e., soil organic carbon, soil physical parameters such as bulk density, and porosity, soil fauna and micro-flora) and that influenced crop growth, N uptake and soil water contents.

A 3-yr study was conducted to determine the effectiveness of N fertilizer application times (at planting vs. sidedress) and N fertilizer source (regular urea vs. coated urea) on N2O emissions and corn (Zea mays L.) grain yields from soil under conventional tillage (CT), zone tillage (ZT), or no-tillage (NT) in southwestern Ontario. On average, 4.19 kg N ha−1 yr−1 were lost from the CT treatments as N2O and these losses were reduced by 16.6% with NT (3.50 kg N ha−1 yr−1) and by 43.8% with ZT (2.35 kg N ha−1). There were some significant effects of N source and application time on N2O emissions; however, these were inconsistent among tillage treatments and years. In 2004, there was a significant interaction between N source and tillage with regular urea (6.49 kg N ha−1) producing 2.7 times more N2O than coated urea (2.40 kg N ha−1) with CT. However, N source did not significantly affect N2O emissions in either 2005 or 2006. In CT treatments, the 3-yr average N2O emissions using N applied at planting (5.02 kg N ha−1 yr−1) were, on average, 49% greater than when sidedress urea (3.37 kg N ha−1 yr−1) was applied. The 3-yr average corn grain yield for CT (9.38 t ha−1) was significantly greater than for NT (8.35 t ha−1), while the yield for ZT (9.01 t ha−1) was not significantly different from either CT or NT. The influence of tillage, N application time and N source on N2O emissions and corn grain yields appeared to be partially related to the amount and timing of precipitation and the root zone soil moisture content. Polymer-coated urea was most effective in 2004 under CT when the soil moisture was high in the first month after planting due to antecedent soil moisture conditions and rainfall. Under these wetter conditions, N2O emissions were reduced by either delaying urea hydrolysis with polymer-coated urea or by using ZT instead of CT.

Innovative management practices are required to increase the efficiency of N fertilizer usage and to reduce nitrous oxide (N2O) and carbon dioxide (CO,) emissions from agricultural soils. The objectives of this study were to evaluate the feasibility of using conservation tillage and N fertilizer placement depth to reduce N2O and CO2 emissions associated with corn (Zea mays L.) production on clay loam soils in Eastern Canada. A 3-yr field study was established on a wheat (Triticum aestivum L.)-corn-soybean [Glycine max (L.) Merr.] rotation with each phase of the rotation present every year. Investigations were focused on the corn phase of the rotation. The tillage treatments following winter wheat included fall moldboard plow tillage (15 cm depth), fall zone-tillage (21 cm width, 15 cm depth), and no-tillage. The N placement treatments were "shallow" placement of sidedress N (2-cm depth) and "deep" placement of sidedress N (10-cm depth). Nitrous oxide emissions were measured 53 times and CO2 emissions were measured 43 times over three growing seasons using field-based sampling chambers. There was a significant tillage and N placement interaction on N2O emissions. Averaged over all three tillage systems and site-years, N2O emissions from shallow N placement (2.83 kg N ha(-1) yr(-1)) were 26% lower than deep N placement (3.83 kg N ha(-1) yr(-1)). The N2O emissions were similar among the tillage treatments when N was placed in the soil at a shallow depth. However, when N was placed deeper in the soil (10 cm), the 3-yr average N2O emissions from zone-tillage (2.98 kg N ha(-1) yr(-1)) were 20% lower than from no-tillage (3.71 kg N ha(-1) yr(-1)) and 38% lower than those from moldboard plow tillage (4.81 kg N ha(-1) yr(-1)). Tillage type and N placement depth did not affect CO2 emissions (overall average = 5.80 Mg C ha(-1) yr(-1)). Hence, zone-tillage and shallow N placement depth reduced N2O emissions without affecting CO2 emissions.

Innovative management practices are required to increase the efficiency of N fertilizer usage and to reduce nitrous oxide (N2O) and carbon dioxide (CO2) emissions from agricultural soils. The objectives of this study were to evaluate the feasibility of using conservation till- age and N fertilizer placement depth to reduce N2O and CO2 emissions associated with corn (Zea mays L.) production on clay loam soils in Eastern Canada. A 3-yr field study was established on a wheat (Triticum aestivum L.)-corn-soybean (Glycine max (L.) Merr.) rota- tion with each phase of the rotation present every year. Investigations were focused on the corn phase of the rotation. The tillage treatments following winter wheat included fall moldboard plow tillage (15 cm depth), fall zone-tillage (21 cm width, 15 cm depth), and no-tillage. The N placement treatments were ''shallow'' placement of sidedress N (2-cm depth) and ''deep'' placement of sidedress N (10-cm depth). Nitrous oxide emissions were measured 53 times and CO2 emissions were measured 43 times over three growing seasons using field-based sampling chambers. There was a significant tillage and N placement interaction on N2O emissions. Averaged over all three tillage systems and site-years, N2O emissions from shallow N placement (2.83 kg N ha 21 yr 21 ) were 26% lower than deep N placement (3.83 kg N ha 21