A 2-year field experiment was carried out to determine the combined effects of planting density and N application rate on the agronomic, economic and environmental benefits of maize production. We set three planting densities (67,500, 75,000 and 82,500 plants ha⁻¹) and five N application rates (0, 100, 200, 300 and 400 kg N ha⁻¹). Increasing planting density improved water use and N uptake, but reduced nitrate in soil. More N inputs over optimal rates decreased NUE and increased nitrate in soil. Compared to the modelling combination of planting density and N application rate that achieved the maximum yield and profit, the modelling combination that achieved the maximum net productive value retained yield and profit, but it used an N application rate that was 12–20% lower, and resulted in an 11–25% decrease in nitrate in soil. The optimal modelling combinations, which were a planting density of 74,387 plants ha⁻¹ and an N application rate of 302 kg N ha⁻¹ in 2017, and 73,528 plants ha⁻¹ and 311 kg N ha⁻¹ in 2018, achieved the maximum net productive values of 2620 $ ha⁻¹ in 2017 and 2693 $ ha⁻¹ in 2018. When the combinations maximized yield and profit, the environmental effect was more sensitive than that of the yield and profit. The optimal combination of planting density and N application rate curtailed N pollution without the great cost of yield and profit, which balanced the agronomic and environmental effect on maize production.

中文翻译：

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种植密度和氮肥施用量平衡玉米的农艺和环境效应

进行了为期两年的田间试验，以确定种植密度和氮肥施用量对玉米生产的农艺，经济和环境效益的综合影响。我们设定了三种种植密度（67,500、75,000和82,500株ha ^-1）和五个氮肥施用量（0、100、200、300和400 kg N ha ^-1）。种植密度的增加改善了水分利用和氮的吸收，但减少了土壤中的硝酸盐。超过最佳比例的氮输入会降低土壤中的氮素含量并增加硝酸盐含量。与实现最大产量和利润的种植密度和氮肥施用量的模拟组合相比，实现最大净生产值的模拟组合保留了产量和利润，但是氮肥施用量降低了12–20％，使土壤中的硝酸盐减少11–25％。最佳建模组合是2017年的种植密度为74,387株ha ^-1和302 kg N ha ^-1的氮肥施用量，以及73,528株ha ^-1和311 kg N ha ^-1到2018年，最大净生产价值达到2017年的2620美元ha ^-1和2018年的2693美元ha ^-1。当这些组合使收益和利润最大化时，对环境的影响比对收益和利润的影响更大。种植密度和氮肥施用量的最佳组合可以减少氮素的污染，而又不会增加产量和利润的成本，从而平衡了农业和环境对玉米生产的影响。