陕西关中小麦-玉米轮作区协调作物产量和环境效应的农田适宜氮肥用量

为了确定陕西关中小麦-玉米轮作区兼顾作物产量和环境效应的农田适宜氮肥用量,通过玉米-小麦-玉米连续3季田间试验研究了作物产量、氮肥利用效率、氮肥表观损失和土壤氮素平衡等对施氮量的响应。结果表明,随着氮肥用量的增加,不同年份作物产量和3季作物累计产量均表现为先增加后降低的趋势,而累计氮肥农学效率、氮肥表观利用率、氮肥吸收效率和氮肥偏生产力均表现为显著的降低趋势。土壤氮素平衡结果表明,随着施氮量的增加,低量施氮时(小麦施N150 kg/hm2,玉米施N180 kg/hm2),氮肥残留显著增加,表观损失和损失率变化不明显,而高量施氮时(小麦施N150 kg/hm2,玉米施N180 kg/hm2),氮肥残留变化不明显,表观损失和损失率却显著增加。回归和相关分析显示,矿质氮在土壤较深层次(100—200cm土层)大量累积是氮肥表观损失的重要途径之一。小麦施N 150 kg/hm2、玉米施N 180 kg/hm2时,作物即可获得相对较高的产量和氮肥利用率,且能保持作物收获前后土壤无机氮库的基本稳定,同时也可将氮肥表观损失降至较低水平。

Optimum-N application rate to maximize yield and protect the environment in a wheat-maize rotation system on the Guanzhong Plain, Shaanxi Province

The objective of this field study was to determine the N application rate which would both maximize yield and protect the environment in a wheat-maize rotation district of the Guanzhong Plain, Shaanxi Province. The study included six treatments replicated three times: N0 (no N application to either wheat or maize), N1 (113 kg N/hm² to wheat + 135 kg N/hm² to maize), N2 (150 kg N/hm² to wheat + 180 kg N/hm² to maize), N3 (188 kg N/hm² to wheat + 225 kg N/hm² to maize), N4 (225 kg N/hm² to wheat + 270 kg N/hm² to maize), and N5 (300 kg N/hm² to wheat + 360 kg N/hm² to maize). The study was conducted over 1.5 yr (maize-wheat-maize). The effects of N application rate on crop yield, N fertilizer use efficiency, apparent N loss, and N budget in the 0-100 cm depth were determined. The results showed that annual crop yield and cumulative crop yield both increased and then decreased as N application rate increased. In contrast, cumulative N agronomic efficiency, apparent N utilization, N uptake efficiency, and N partial productivity decreased significantly as N application rate increased. Calculation of the N budget in the 0-100 cm depth showed that residual mineral-N concentrations were significantly higher in the N2 treatment than in the N1 treatment, but apparent N loss and loss rates were nearly the same in the two treatments. In contrast, residual mineral-N concentrations were nearly the same in the N3, N4, and N5 treatments, but apparent N loss and loss rate increased significantly in the order N3 < N4 < N5. Regression and correlation analysis indicated that excessive N fertilizer application resulted in the build-up of mineral-N concentrations in the deep soil profile. This build-up contributed significantly to apparent N loss. In conclusion, the application of 150 kg N/hm² to wheat and 180 kg N/hm² to maize resulted in relatively high yield and N use efficiency. These application rates also maintained residual mineral-N concentrations and reduced apparent N losses.