The combination of mulch with N fertilizer application is a common agronomic technique used in the production of rainfed maize (Zea mays L.) to achieve higher yields under conditions of optimum planting density and adequate N supply. However, the combined effects of mulch, planting density, and N fertilizer application rate on plant N uptake and N translocation efficiency are not known. The objective of this study was to quantify the interaction effect of mulch, planting density, and N fertilizer application rate on maize grain yield, N uptake, N translocation, and N translocation efficiency. The experiment was arranged in a randomized complete block design with three factors (2 mulch levels × 2 planting densities × 4 N fertilizer application rates) replicated four times. There was a significant interaction among mulch, plant density, and N fertilizer on maize grain yield, kernel number per cob, N uptake, N translocation, and N translocation efficiency. Averaged over the 3 years of the study, total plant N uptake at silking ranged from 79 to 149 kg N ha− 1 with no mulch and from 76 to 178 kg N ha− 1 with mulch. The N uptake at silking in different plant organs ranked as leaf > grain > stem > cob. Averaged across all factors, the highest N translocation was observed in leaves, which was 59.4 and 88.7% higher than observed in stems and ears, respectively. The mean vegetative organ N translocation efficiency averaged over mulch, planting density, and N fertilizer application rate treatments decreased in the order of leaf > stem > cob. Mulch, planting density, and N fertilizer application rate not only have significant effects on improving maize grain yield and NUE, but also on N uptake, N translocation, and N translocation efficiency. Our results showed clearly that under high planting density, the combination of mulch and moderate N fertilizer application rate was the optimal strategy for increasing maize grain yield and N use efficiency.

中文翻译：

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确定最佳覆盖，种植密度和施氮量，以增加西北地区玉米的产量和氮素转运效率。

覆盖与氮肥的结合使用是雨养玉米（Zea mays L.）生产中常用的农艺技术，可在最佳种植密度和充足氮素供应的条件下实现更高的单产。但是，覆盖，种植密度和氮肥施用量对植物氮吸收和氮转运效率的综合影响尚不清楚。这项研究的目的是量化覆盖，种植密度和氮肥施用量对玉米籽粒产量，氮素吸收，氮素转运和氮素转运效率的相互作用影响。实验以随机完整区组设计进行安排，其中三个因素（2个覆盖水平×2个种植密度×4 N施肥量）重复了四次。覆盖物，植物密度，氮肥对玉米籽粒产量，单穗粒数，氮素吸收，氮素转运和氮素转运效率的影响。在研究的3年中平均，未覆盖时植物总氮吸收量在79到149 kg N ha-1之间，在覆盖时的植物N吸收量在76到178 kg N ha-1之间。不同植物器官在丝化时的氮吸收量依次为叶>谷粒>茎>穗轴。在所有因素中平均，在叶片中观察到最高的N转运，分别比在茎和穗中观察到的高59.4和88.7％。在覆盖，种植密度和施氮量下，平均营养器官的平均氮素转运效率按叶>茎>穗轴的顺序降低。覆盖，种植密度和氮肥施用量不仅对提高玉米籽粒产量和NUE，而且还涉及氮素吸收，氮素易位和氮素易位效率。我们的结果清楚地表明，在高种植密度下，覆盖和适量施氮肥是提高玉米籽粒产量和氮素利用效率的最佳策略。