减氮适墒对冬小麦土壤硝态氮分布和氮素吸收利用的影响

【目的】针对黄淮冬麦区过量施氮的现象,研究了适量减氮在不同土壤墒情下硝态氮分布以及冬小麦对氮素吸收利用效率和籽粒产量的变化,为该地区小麦生产上科学施用氮肥提供理论依据。【方法】于2014—2015和2015—2016两个小麦生长季,在大田条件下设置3个灌水处理,自然降水(W1)、适墒(W2,70%±5%)、足墒(W3,80%±5%)和3个施氮量处理(不施氮,N1;减氮施肥,N2:195 kg·hm~(-2);常规高量氮肥,N3:270 kg·hm~(-2)),测定了0—100 cm土层硝态氮含量、冬小麦植株氮素吸收转运量和籽粒产量。【结果】0—60 cm土层硝态氮(NO_3-N)的分布随土层加深而减少,随施氮量增加而提高,随土壤墒情的增大而减少;60 cm又出现不同程度的回升,尤其是足墒(W3)加大了NO_3-N的淋溶,N2、N3水平下80—100 cm土层W3平均比W1高出了3.8 mg·kg~(-1)和4.2 mg·kg~(-1);减氮处理(N2)促进了NO_3-N吸收,成熟期0—20 cm土层NO_3-N比开花期平均降幅为2.3 mg·kg~(-1),高氮处理(N3)收获后土层中NO_3-N却有较多的富集。减氮适墒处理(W2N2)显著增加了开花期营养器官氮素积累量(P0.05),并促进氮素向籽粒的有效转运,尤其表现在叶片中;花前氮素转移量和对籽粒的贡献率均达最大,籽粒产量和籽粒中的氮素积累量分别比其他处理平均高出15.4%、27.3%,从而极显著提高了氮素吸收率和生产效率(P0.05)。【结论】本试验条件下,施氮量195 kg·hm~(-2),拔节后土壤相对含水量维持在70%±5%,是兼顾产量、氮肥吸收和生产效率的最佳处理。

Effects of Nitrogen-Reducing and Suitable Soil Moisture on Nitrate Nitrogen Distribution in Soil,Nitrogen Absorption and Utilization of Winter Wheat

【Objective】The objective of this experiment was to study the effect of reduced nitrogen(N) application under different soil moisture on the nitrate nitrogen (NO₃-N) distribution in soil, N absorption, use efficiency in plant and grain yield of winter wheat. This study will provide a scientific basis for rational N application in Huang-Huai plain.【Method】To determine NO₃-N content in different soil layers of 0-100 cm soil depth, N accumulation, N translocation amount and grain yield of winter wheat, we established a split-plot experiment for two consecutive years (2014-2015 and 2015-2016) in field, i.e. three levels of soil moisture, water deficits to no irrigation (W1), water-savingirrigation to 70%±5% of soil relative moisture after jointing stage (W2) and adequate irrigation to 80%±5% of soil relative moisture after jointing stage (W3); three levels of nitrogen: 0 (N1), 195 kg·hm^-2 (N2) and 270 kg·hm^-2 (N3).【Result】The content of NO₃-N in 0-60 cm soil layer decreased with the layer''s deepening, and soil water content and N application input amount increased; whereas the NO₃-N content in 60-100 cm soil layers increased, especially under W3 treatment. Besides, soil NO₃-N content of 80-100 cm soil layer at N2 and N3 under high supplemental irrigation condition (W3) increased by 3.8 mg·kg^-1 and 4.2 mg·kg^-1, respectively, compared with that under no irrigation (W1). N2 treatment had higher NO₃-N content of 0-20 cm soil layer at anthesis, increased by 2.2 mg·kg^-1 than that at maturity; whereas there was more NO₃-N residue underhighNapplication (N3) at post-harvest. The results also showed that N translocation amount in vegetative organs ordered by leaf > stem> sheath. In addition, W2 with N2 treatment had the largest N accumulation amount in plant at anthesis, pre-antheis N translocation amount (N accumulation in vegetative organs at anthesis minus the N accumulation in vegetative organs at maturity, NTA) and the contribution of N remobilized to grain (NTA/ N accumulation in vegetative organs at maturity stage, NRC) from vegetative organs after anthesis. Similarly, the grain yield and N accumulation amount in grain under W2 with N2 treatment were 15.4% and 27.3% higher than that at other treatments, respectively. Those increases would improve N uptake efficiency and N fertilizer productive efficiency under W2 with N2 treatment (P＜0.05).【Conclusion】Considering the yield, N uptake efficiency, N fertilizer productive efficiency and soil nitrogen balance, reducing N application from 270 to 195 kg·hm^-2 under suitable soil moisture (water-saving) is optimal in Huang-Huai Rivers Valley wheat region.