绿洲灌区密植对氮肥减量玉米产量的补偿潜力

Compensation Potential of Dense Planting on Nitrogen Reduction in Maize Yield in Oasis Irrigation Area

【目的】针对绿洲灌区玉米生产氮肥用量过高的问题,探究通过密植补偿氮肥减量对玉米产量负效应的可行性。【方法】2019—2021年,以施氮水平为主区,设地方习惯施氮(N_(2),360 kg·hm^(-2))、减量25%施氮(N_(1),270 kg·hm^(-2))两个水平;以种植密度为副区,设传统(M_(1),7.8万株/hm^(2))、中(M_(2),10.4万株/hm^(2),增密33%)、高(M3,12.9万株/hm^(2),增密66%)3个密度水平,进行裂区试验,重点研究氮肥减量条件下增密对玉米产量及其构成因素的影响。【结果】(1)氮肥减量导致玉米籽粒产量、生物产量分别降低4.0%、4.9%。减氮条件下,中密度可以产生籽粒产量补偿效应,N_(1)M_(2)较对照N_(2)M_(1)提高4.1%;高密度处理N_(1)M3生物产量补偿效应最大,较对照提高14.2%。(2)通过回归分析模拟得到:减氮条件下,当种植密度提高至8.4万株/hm^(2)可以与对照N_(2)M_(1)籽粒产量持平,并在10.6万株/hm^(2)时获得最大产量13537kg·hm^(-2),较对照提高4.9%。(3)氮肥减量引起穗数、穗粒数和千粒重分别降低5.0%、3.3%和3.4%;中、高密度分别较传统密度提高穗数27.9%、49.7%,降低穗粒数3.8%、8.4%,降低千粒重5.2%、8.9%。中密度较传统密度对收获指数无显著影响,而高密度使收获指数降低14.2%。N_(1)M_(2)较对照N_(2)M_(1)通过穗数增加补偿了减氮引起穗数、穗粒数及千粒重的下降,从而实现丰产。(4)氮肥减量降低拔节期至抽雄吐丝期的玉米生长率7.2%—8.4%;中、高密度较传统密度提高苗期至大喇叭口期玉米生长率27.3%、60.3%。(5)氮肥减量条件下,N_(1)M_(2)较对照提高叶、茎和鞘干物质转运量达9.6%、13.6%和3.7%,提高叶和茎对籽粒产量的贡献率5.3%和9.0%。【结论】通过合理密植可以补偿减氮引起的玉米产量下降,在施氮量270 kg·hm^(-2)的基础上增密至10.4万株/hm^(2),能够最大化产量补偿效应,是绿洲灌区玉米节氮稳产丰产的可行措施。

【Objective】To address the issue of excessive nitrogen fertilizer use for maize production in an oasis irrigation area,this study investigated the compensation effect for nitrogen fertilizer reduction through dense planting on maize yield.【Method】From 2019 to 2021,a two-factor split-plot experiment was carried out to explore the effect of different maize densities on yield and yield components under nitrogen reduction conditions.The main plot was two nitrogen application rate,including 25%reduction(N_(1),270 kg·hm^(-2))and local habitual nitrogen application(N_(2),360 kg·hm^(-2)),and sub-plot was three planting densities of maize,including traditional(M_(1),78000 plants/hm^(2)),medium(M_(2),104000 plants/hm^(2),33%increase),and high planting density(M3,129000 plants/hm^(2), 66% increase).【Result】(1) The grain yield and biomass of maize under N_(1) decreased by 4.0% and 4.9% than that under N_(2) respectively due to nitrogen reduction, which could be compensated by dense planting. The grain yield of N_(1)M_(2) was increased by 4.1% compared with that of the control treatment (N_(2)M_(1)), while the biomass of treatment of high density and nitrogen reduction (N_(1)M3) had the largest compensation effect, which was increased by 14.2% compared with that under the control. (2) According to the regression analysis, at the N_(1) level, the density of 84 000 plants/hm^(2) could get the equal grain yield of the control treatment, and reached the maximum grain yield of 13 537 kg·hm^(-2) at 106 000 plants/hm^(2), achieving a 4.9% increase in grain yield. (3) Compared with N_(2), N_(1) reduced maize ear number, kernel number per ear, and 1 000-kernel weight by 5.0%, 3.3%, and 3.4%, respectively, but had no significant effect on the harvest index. M_(2) and M3 increased the maize ear number by 27.9% and 49.7%, reduced kernel number per ear by 3.8% and 8.4%, respectively, and decreased 1 000-kernel weight by 5.2% and 8.9%, respectively. M_(2) had no significant effect on the harvest index, while M3 significantly reduced the harvest index by 14.2%. Therefore, compared with N_(2)M_(1), N_(1)M_(2) compensated for the decrease in ear number, kernel number per ear, and 1 000-kernel caused by nitrogen reduction through the increase of ear number. (4) N_(1) decreased the maize growth rate from the jointing stage to the tasseling and silking stage by 7.2%-8.4%, while M_(2) and M3 significantly increased the maize growth rate by 27.3% and 60.3% compared with traditional density from the seedling stage to the trumpet stage. (5) Compared with N_(2)M_(1), N_(1)M_(2) increased maize leaf,stem, and sheath dry matter transportation amount (DTA) by 9.6%, 13.6%, and 3.7%, respectively, and the contribution rate of vegetative organs to grain (GCR) by 5.3% and 9.0%, respectively.【Conclusion】In the oasis irrigation area, the maize grain yield decrease caused by nitrogen reduction could be compensated by reasonably dense planting. Increasing the density to 104 000 plants/hm^(2) based on 25% nitrogen reduction could maximize the yield compensation effect, which was a feasible measure to save nitrogen for a stable and high yield of maize.