晚播减氮对不同氮肥基追比例下小麦产量和氮素利用效率的影响

Effect of nitrogen reduction in late sowing on wheat yield and nitrogen use efficiency under different nitrogen base and topdressing ratios

【目的】探寻江汉平原晚播小麦减少氮肥施用量的可行性及合理的减氮模式。【方法】在大田试验条件下,以郑麦9023为供试材料,设置正常播和晚播2个播期,并在2个播期下分别设置3个施氮量处理,每个施氮量下设置2个基追比处理,比较了不同处理间小麦产量及其构成因素、氮素相关指标的变化。【结果】①同一施氮量及底追比例条件下,播期推迟,籽粒产量显著降低,其产量构成因素穗数、千粒重均显著降低。进一步分析表明,播期推迟,开花期和成熟期总干物质积累量降低;其中开花期总干物质量的变化主要归因于叶片和茎鞘干物质积累量显著减少,而穗干物质积累量无显著变化;成熟期干物质积累量的变化则与叶片、茎鞘和穗轴与颖壳有关。同一施氮量及底追比例条件下,播期推迟,植株开花期和成熟期氮素积累量降低,其中晚播小麦开花期叶片含氮量增加,开花期茎鞘、成熟期茎鞘和穗轴与颖壳的含氮量减少;同一施氮量及底追比例条件下,播期推迟,成穗率和氮素利用效率均显著降低。②同一播期不同氮肥处理间比较,晚播条件下,可减少氮肥施用量:在本试验条件下,施氮量由180 kg/hm^(2)减少至150 kg/hm^(2),晚播小麦产量差异不显著,在2019—2020年分别降低3.33(M_(1))、293.34 kg/hm^(2)(M_(2)),在2020—2021年分别降低158.67(M_(1))、13.50 kg/hm^(2)(M_(2)),均远低于正常播期降低幅度;究其原因晚播小麦在减氮至150 kg/hm^(2)时,穗数和穗粒数更为稳定,而千粒重在一定程度上有所增加。进一步减少施氮量,两个播期下产量变化均未达到显著水平。同一底追比例条件下,减氮,开花期茎鞘和穗含氮量显著降低,干物质积累量无显著变化,成熟期穗轴与颖壳含氮量显著降低,干物质积累量无显著变化;同一播期和底追比例条件下,减氮,成穗率均显著上升,M_(1)氮素利用效率显著上升,M_(2)氮素利用效率保持稳定。【结论】江汉平原地区,在氮肥运筹模式不断优化条件下,晚播小麦减氮处理产量与正常氮量产量相比降低不显著,但成穗率和氮素利用效率显著提高;播期推迟20 d内,推荐氮肥运筹模式为:m(基追比例为底肥)∶m(冬前追肥)∶m(拔节期追肥)=1∶1∶1,施氮量可由正常施氮量降为150 kg/hm^(2)。

【Objective】The present paper aimed to explore the feasibility of reducing the amount of nitrogen fertilizer and a reasonable nitrogen reduction model under late sowing wheat in the Jianghan Plain.【Method】Field experiments were conducted with Zhengmai 9023 under traditional and late sowing date with three nitrogen treatments differing in ratios of basal to topdressing.The changes in wheat yield and its constituent factors and nitrogen related indicators were compared across treatments.【Result】(i)Under the same nitrogen application rate and base-topdressing ratio,grain yield,panicle number and 1000-grain weight were significantly reduced delayed the sowing date.Reduced total dry matter accumulation during flowering and maturity under late sowing was due to the decrease in dry matter accumulation in leaves and stem sheaths;The dry matter accumulation in spike did not show significant change.The changes in dry matter accumulation at maturity were related to leaves,stem+sheaths and grain husk+spike axis.Under the same nitrogen application rate and base-topdressing ratio,the nitrogen accumulation in wheat at flowering and maturity decreased as well;Nitrogen accumulation in flowering leaves of increased under late sowing,but nitrogen accumulation in stem+leaf sheath,ripe leaves and ripe grain husk+spike axis decreased.Under the same nitrogen application rate and base-topdressing ratio,the spike formation rate and nitrogen use efficiency were significantly reduced under late sowing.(ii)Under different nitrogen fertilization treatments and the same sowing date,nitrogen fertilization can be reduced from 180 to 150 kg/hm^(2)under late sowing with insignificant change in yield decreased by 3.33 kg/hm^(2)(M)and 293.34 kg/hm^(2)(M)in 2019—2020;158.67 kg/hm^(2)(M_(1))and 13.50 kg/hm^(2)(M_(2))in 2020—2021.The reduction was much lower than that of normal sowing,and the reason was that the number of spikes and grain number per spike were stable when the nitrogen application rate was reduced from 180 to 150 kg/hm^(2),and the 1000-grain weight increased to some extent.Further reducing the amount of nitrogen applied,the yield change under the two sowing dates did not reach a significant level.Under the same base-topdressing ratio,reducing nitrogen application rate,the nitrogen accumulation in the stem+leaf sheath and spike at the flowering stage and grain husk+spike axis were significantly reduced,but dry matter accumulation did not change significantly.Under the same sowing date and base-topdressing ratio,reducing nitrogen application rate,spike formation rate increased significantly,Mnitrogen utilization efficiency increased significantly,and Mnitrogen utilization efficiency remained stable.【Conclusion】Under the conditions of continuous optimization of nitrogen fertilizer management mode,the yield of late sowing wheat under nitrogen reduction treatment was not significantly reduced compared with normal nitrogen yield,but the spike formation rate and nitrogen use efficiency were significantly improved.After a delay of 20 days,the recommended nitrogen fertilizer management model is that the ratio of base to topdressing is m(base fertilizer)∶m(top dressing before winter)∶m(top dressing at jointing stage)=1∶1∶1,and the nitrogen application rate can be reduced from the normal nitrogen application rate to 150 kg/hm^(2).