Developing best management practices for late nitrogen applications in corn

包括消费者在内的整个农业食品价值链上的利益相关者一再表示，他们希望在不牺牲竞争力（价格或质量）的情况下，最大限度地减少对环境的影响。为玉米生产开发更合理的氮肥管理策略将使加拿大农民同时实现这两个目标。氮肥损失对全球氮素生物地球化学循环和区域养分污染有着深远的影响，但对农民来说也代表着显著的经济低效。我们建议改进一种基于“后期”氮肥施用的氮肥策略，在比传统做法晚得多的季节施用氮肥。大多数农民在种植前后施用氮肥，但后期施氮策略在种植季后期施用大部分氮肥，约在种植后2.5个月。该策略的好处是在玉米氮素吸收率高的时候同步施用氮肥，从而降低了高氮素损失的风险。此外，由于氮肥是在季中施用的，后期氮肥策略也允许农民改进他们施用的氮肥量。播种后等待2.5个月，农民可以评估天气、土壤和其他变量，以帮助他们更好地确定应该施用的氮肥。在种植过程中施用氮肥的农民就没有这种奢侈。随着农民对后期氮肥管理越来越感兴趣，在加拿大和其他地方开展了验证后期氮肥管理的概念验证研究。有必要制定最佳管理实践，使后期氮肥策略对农民的效益最大化，并减少氮肥使用的有害影响。该伙伴关系将为后期施氮建立最佳管理实践，量化粮食产量、经济回报、氮挥发损失以及其他与氮有关的作物和土壤变量。

Stakeholders along the entire agri-food value chain, including consumers, have repeatedly stated their desire for food production practices that minimize environmental impacts without sacrificing competitiveness (price or quality). Developing more rational nitrogen (N) fertilizer management strategies for corn production would allow Canadian farmers to meet both goals simultaneously. Fertilizer N losses have a profound impact on global N biogeochemical cycling and regional nutrient pollution, but they also represent a significant economic inefficiency for the farmer. We are proposing to refine an N fertilizer strategy based on 'late' N fertilizer applications, applying N fertilizer much later in the season than traditionally done. Most farmers apply N fertilizer around planting, but late N strategies apply a large proportion of this N much later in the season, about 2.5 months after planting. This strategy has the benefit of synchornizing the application of fertilizer N to when corn N uptake rates are high, which reduces the risk of high N losses. Moreover, because fertilizer N is applied mid-season, late N strategies also allow farmers to refine the N rate they apply. Waiting 2.5 months after planting allows farmers to assess weather, soil and other variables to help them better determine the N rate they should apply. A farmer applying N around planting does not have this luxury. Proof-of-concept studies validating late N management have been carried out in Canada and elsewhere as farmers are increasingly interested in the strategy. There is a need to develop best management practices that maximize the benefits of late N strategies for farmers and reduce the deleterious impacts of N fertilizer use. The partnership will establish best management practices for late N applications, quantifying grain yield, economic returns, N volatilization losses and other N-related crop and soil variables.