To establish the optimal fertilization rate to maintain high wheat yield and low environmental risk in the North China Plain, a two-year field experiment (2016–2018) was conducted with six combinations of two N rates (N0; N1: 240 kg ha −1 ) and three P rates (P0; P1: 150 kg ha −1 ; P2: 240 kg ha −1 ) to investigate the effects of these regimes on wheat grain yield, N assimilatory enzyme activity (nitrate reductase, NR and glutamine synthetase, GS), N use efficiency (NUE) and soil nitrate nitrogen distribution. Results showed that N application increased grain yield and grain protein concentration (GPC) significantly, in association with increased residual soil nitrate in both growing seasons, across the three P application rates. Only P application had no effect on these parameters. Significant interactions of N and P fertilizer were found on most of the tested parameters. Highest grain yield, GPC and NUE, and the lowest residual soil nitrate were observed under the treatment of N1P1. N accumulation in plant was highly correlated with grain yield and NUE, and N assimilatory enzyme activity at flowering was highly correlated with grain yield and GPC, which contributed to achieving high yield and NUE simultaneously. Regression analysis showed that the response of grain yield, NUE and residual soil nitrate to P rates fitted quadratic model, in which the maximum values of grain yield, NUE and the lowest residual soil nitrate were obtained at the extent of P rate 140 ~ 150 kg P ha −1 . Hence, we recommended fertilizer rate of N 240 kg ha −1 and P 150 kg ha −1 as the optimal nitrogen-phosphorus regime in the North China Plain, which can maintain higher crop yield while lower environmental risk.

中文翻译：

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华北平原氮磷互作对小麦产量、氮素利用效率及土壤硝酸盐氮分布的影响

为了确定华北平原保持小麦高产和低环境风险的最佳施肥量，进行了为期两年的田间试验（2016-2018），使用两种施氮量的六种组合（N0；N1：240 kg ha - 1 ) 和三个磷比率 (P0; P1: 150 kg ha -1 ; P2: 240 kg ha -1 ) 以研究这些制度对小麦籽粒产量、N 同化酶活性（硝酸还原酶、NR 和谷氨酰胺合成酶、 GS)、氮利用效率 (NUE) 和土壤硝态氮分布。结果表明，施氮显着增加了谷物产量和谷物蛋白质浓度（GPC），这与两个生长季节中残留土壤硝酸盐的增加有关，在三个施磷率中。只有 P 应用对这些参数没有影响。在大多数测试参数中发现 N 和 P 肥料之间存在显着的相互作用。在N1P1处理下观察到最高的粮食产量、GPC和NUE，以及最低的土壤硝酸盐残留。植株氮素积累与籽粒产量和NUE高度相关，开花期氮同化酶活性与籽粒产量和GPC高度相关，有助于同时实现高产和NUE。回归分析表明，粮食产量、NUE和土壤残留硝酸盐对P率的响应拟合二次模型，其中在P率140～150 kg范围内获得了粮食产量、NUE和最低土壤残留硝酸盐的最大值P ha -1 。因此，我们推荐N 240 kg ha -1 和P 150 kg ha -1 的施肥量作为华北平原的最佳氮磷施用量，