“…Responses of CO 2 -eq emissions Contrary to our hypothesis, the use of EEFs did not reduce net CO 2 -eq emissions relative to untreated urea in rain-fed winter wheat systems. Other studies also displayed no effect or a small effect of EEFs on CO 2 -eq emission reductions in rain-fed winter wheat systems (An et al 2021;Besen et al 2021). Benefits of using EEFs to reduce CO 2 -eq emissions may not to be appreciable in rain-fed winter wheat systems.…”
Section: Responses Of Yield Components and Seedling Vigourmentioning
Optimizing the timing of nitrogen (N) enhanced efficiency fertilizers (EEFs) may maximize winter wheat (Triticum aestivum L.) grain yield, protein content, and N-use efficiency (NUE). From 2013 to 2018, experiments were conducted at two irrigated and six rain-fed sites across the Canadian Prairies (24 site-years) to evaluate winter wheat responses to N source and timing/placement effects of EEFs. Nitrogen sources included untreated urea, nitrification inhibitor nitrapyrin treated urea (Nitrapyrin), urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) plus nitrification inhibitor dicyandiamide (DCD) treated urea (NBPT+DCD), and polymer-coated urea (PCU). The N sources were all side-banded at planting, 30% side-banded at planting plus 70% broadcast in-crop late-fall (averaged 38 days after planting; split-applied late-fall) or 30% side-banded at planting plus 70% broadcast in-crop early-spring (averaged 224 days after planting; split-applied early-spring). Nitrous oxide and methane emissions were measured at one rain-fed site to test whether N source and timing/placement influenced CO2-equivalents (CO2-eq; nitrous oxide+methane). Under irrigation, NBPT+DCD consistently produced the highest yields regardless of timing/placement; however, the 80% of recommended rate caused sub-optimal protein responses (≤11%) unless split-application of N was adopted. . Untreated urea produced the highest net CO2-eq and yield-scaled CO2-eq emissions, with the highest emissions when urea was split-applied early-spring. To optimize winter wheat production and NUE, we conclude that NBPT+DCD all-banded during seeding operations or split-applied early-spring provided similar and often superior results than other sources including a more typical system of urea side-banded at the time of seeding.
“…Responses of CO 2 -eq emissions Contrary to our hypothesis, the use of EEFs did not reduce net CO 2 -eq emissions relative to untreated urea in rain-fed winter wheat systems. Other studies also displayed no effect or a small effect of EEFs on CO 2 -eq emission reductions in rain-fed winter wheat systems (An et al 2021;Besen et al 2021). Benefits of using EEFs to reduce CO 2 -eq emissions may not to be appreciable in rain-fed winter wheat systems.…”
Section: Responses Of Yield Components and Seedling Vigourmentioning
Optimizing the timing of nitrogen (N) enhanced efficiency fertilizers (EEFs) may maximize winter wheat (Triticum aestivum L.) grain yield, protein content, and N-use efficiency (NUE). From 2013 to 2018, experiments were conducted at two irrigated and six rain-fed sites across the Canadian Prairies (24 site-years) to evaluate winter wheat responses to N source and timing/placement effects of EEFs. Nitrogen sources included untreated urea, nitrification inhibitor nitrapyrin treated urea (Nitrapyrin), urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) plus nitrification inhibitor dicyandiamide (DCD) treated urea (NBPT+DCD), and polymer-coated urea (PCU). The N sources were all side-banded at planting, 30% side-banded at planting plus 70% broadcast in-crop late-fall (averaged 38 days after planting; split-applied late-fall) or 30% side-banded at planting plus 70% broadcast in-crop early-spring (averaged 224 days after planting; split-applied early-spring). Nitrous oxide and methane emissions were measured at one rain-fed site to test whether N source and timing/placement influenced CO2-equivalents (CO2-eq; nitrous oxide+methane). Under irrigation, NBPT+DCD consistently produced the highest yields regardless of timing/placement; however, the 80% of recommended rate caused sub-optimal protein responses (≤11%) unless split-application of N was adopted. . Untreated urea produced the highest net CO2-eq and yield-scaled CO2-eq emissions, with the highest emissions when urea was split-applied early-spring. To optimize winter wheat production and NUE, we conclude that NBPT+DCD all-banded during seeding operations or split-applied early-spring provided similar and often superior results than other sources including a more typical system of urea side-banded at the time of seeding.
Maintaining or even increasing crop yields while reducing nitrous oxide (N2O) emissions is necessary to reconcile food security and climate change, while the metric of yield‐scaled N2O emission (i.e., N2O emissions per unit of crop yield) is at present poorly understood. Here we conducted a global meta‐analysis with more than 6000 observations to explore the variation patterns and controlling factors of yield‐scaled N2O emissions for maize, wheat and rice and associated potential mitigation options. Our results showed that the average yield‐scaled N2O emissions across all available data followed the order wheat (322 g N Mg−1, with the 95% confidence interval [CI]: 301–346) > maize (211 g N Mg−1, CI: 198–225) > rice (153 g N Mg−1, CI: 144–163). Yield‐scaled N2O emissions for individual crops were generally higher in tropical or subtropical zones than in temperate zones, and also showed a trend towards lower intensities from low to high latitudes. This global variation was better explained by climatic and edaphic factors than by N fertilizer management, while their combined effect predicted more than 70% of the variance. Furthermore, our analysis showed a significant decrease in yield‐scaled N2O emissions with increasing N use efficiency or in N2O emissions for production systems with cereal yields >10 Mg ha−1 (maize), 6.6 Mg ha−1 (wheat) or 6.8 Mg ha−1 (rice), respectively. This highlights that N use efficiency indicators can be used as valuable proxies for reconciling trade‐offs between crop production and N2O mitigation. For all three major staple crops, reducing N fertilization by up to 30%, optimizing the timing and placement of fertilizer application or using enhanced‐efficiency N fertilizers significantly reduced yield‐scaled N2O emissions at similar or even higher cereal yields. Our data‐driven assessment provides some key guidance for developing effective and targeted mitigation and adaptation strategies for the sustainable intensification of cereal production.
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