施氮量对滴灌冬小麦–夏玉米周年产量及氮素利用效率的影响

  【目的】  当前华北平原冬小麦–夏玉米生产中，存在氮肥投入量大、氮肥利用效率低等问题，在滴灌水肥一体化条件下研究施氮量对冬小麦–夏玉米周年产量、氮素利用效率和土壤全氮含量、硝态氮残留的影响，以期为该地区小麦–玉米节肥、高产高效的栽培模式提供理论依据。  【方法】  于2018—2020年在青岛农业大学胶州现代农业示范园开展小麦、玉米滴灌施肥田间试验。设冬小麦/夏玉米生长季不施氮(N0)和施氮 150/150 kg/hm2 (N1)、210/225 kg/hm2 (N2) 和270/300 kg/hm2 (N3) 4个水平，以传统施肥方式和常规施氮量240/240 kg/hm2为对照(CK)。分析冬小麦和夏玉米产量、氮素吸收量和土壤氮素残留量。  【结果】  N2处理冬小麦、夏玉米产量最高，与N3处理无显著差异，但显著高于N0、N1和CK处理；N3处理冬小麦、夏玉米的干物质积累量、氮素吸收量最高，与N2处理差异较小，而显著高于N0、N1和CK处理。冬小麦、夏玉米氮肥偏生产力随着施氮量的提高而降低；冬小麦季氮素利用效率随着施氮量的提高而降低；夏玉米季，N2、N1和N0处理的氮素利用效率显著高于N3和CK处理，且N0、N1和N2处理间无显著差异；冬小麦、夏玉米氮肥农学利用率均随着施氮量的提高而降低，N2施氮水平下，氮素利用效率和氮肥农学利用率均表现较优。随着施氮量的增加，0—100 cm土层土壤全氮含量和硝态氮含量呈增加的趋势，全氮积累主要集中在0—40 cm土层，N3、N2和CK处理0—100 cm土层土壤全氮含量与N0和N1处理之间的差异随着轮作年数的增加而逐渐增大，N2处理较N3和CK处理有效抑制了硝态氮在表层土壤的积累和向深层土壤的迁移，降低了硝态氮淋失风险。  【结论】  冬小麦季施氮210 kg/hm2和夏玉米季施氮225 kg/hm2 (N2)可实现周年作物增产高效，提高氮素利用效率，显著降低硝态氮向深层土壤迁移，降低硝态氮淋失风险，是滴灌水肥一体化下华北平原麦玉周年轮作适宜的施氮量。

Effects of nitrogen application rate on annual yield and N-use efficiency of winter wheat-summer maize rotation under drip irrigation

  【Objectives】  Fertigation is a water and fertilizer efficient technology in crop production. We studied the suitable N application rate in winter wheat-summer maize production in North China Plain to achieve high N fertilizer efficiency and low soil N loss.  【Methods】  The fertigation experiment in the winter wheat/summer maize system was carried out in Jiaozhou Modern Agricultural Demonstration Park, Qingdao Agricultural University, from 2018 to 2020. The nitrogen fertilization treatment levels for wheat/maize were no N input (N0), 150/150 kg/hm2 (N1), 210/225 kg/hm2 (N2), and 270/300 kg/hm2 (N3), taking the N 240/240 kg/hm2 under conventional irrigation method as the control (CK). The crop yield, N use efficiency, and soil N residue were analyzed.   【Results】  The winter wheat and summer maize yields in N2 and N3 were higher than in other treatments (P<0.05). The dry matter and N accumulation of winter wheat and summer maize in N2 and N3 were higher than in N1 and CK (P<0.05). The N partial factor productivity (NPFP) of winter wheat and summer maize decreased with increasing N levels. N use efficiency declined in the winter wheat season with increasing N levels. In the summer maize season, N use efficiency in N2, N1 and N0 treatments were similar and higher than N3 and CK (P<0.05). The N agronomic efficiency of winter wheat and summer maize decreased with increasing N levels. The highest N use efficiency and N agronomic efficiency were recorded in N2. With the increasing of N levels, the total N and nitrate N content in the 0–100 cm soil layer showed a rising trend. The total N accumulation was mainly concentrated in the 0–40 cm soil layer. The difference in soil total N content between N3, N2, CK and N0, N1 in 0–100 cm soil layer increased as the rotation year advanced. Compared with N3 and CK, N2 effectively inhibited the accumulation of nitrate N in the surface soil layer and its migration to the deeper soil layer, reducing the risk of nitrate leaching.  【Conclusions】  Applying N 210 and 225 kg/hm2 in winter wheat and summer maize (N2) recorded the highest crop yield and biomass, relatively high N use efficiency, and reduced nitrate N migration to the deeper soil layer. Thus, adopting the N2 application rate for wheat and maize is appropriate in the North China Plain under drip fertigation.