苗期渍水和氮肥用量对直播冬油菜产量及氮肥利用率的影响

【目的】秋涝是冬油菜生产中的常见限制因子，本研究通过大田试验研究苗期渍水和氮肥用量对直播冬油菜产量及氮肥利用率的影响，以期为渍水胁迫下直播冬油菜氮肥合理施用提供理论依据。【方法】 选用华油杂9号为试验材料，采用直播栽培方式。两因素裂区试验设计，主处理为土壤水分状况，包括排水处理和苗期渍水处理，副处理为6个氮肥水平，施氮量分别为0、60、120、180、240和300 kg/hm2。研究各试验处理直播冬油菜在苗期、薹期、花期和成熟期的生长状况，各时期的干物质、氮素累积以及氮肥利用效率，同时对籽粒产量及其构成因素做了相应调查。【结果】 苗期渍水明显抑制了直播冬油菜生长发育和产量形成。相同氮肥水平下，与排水处理相比，渍水处理冬油菜各生育期叶片数、叶面积和SPAD值均有不同程度下降，生育期干物质量降幅为19.1%~26.5%，收获指数减少了5.2个百分点。渍水处理显著降低了籽粒产量，减产达23.6%，成苗密度和单株角果数下降是引起产量降低的重要原因，分别下降7.6%和20.4%。此外，渍水处理明显影响了冬油菜氮素吸收，渍水处理冬油菜生育期植株氮含量较排水处理下降了8.0个百分点，氮素累积量降幅为23.2%~32.4%。渍水处理引起了氮肥偏生产力、农学利用率和表观利用率的下降，降幅分别为22.8%、20.4%和18.6%。氮肥可以缓解苗期渍水造成的产量损失，并且缓解效应与氮肥投入量存在直接关系。施氮显著提高了冬油菜叶片数、叶面积和SPAD值，增加了冬油菜成苗密度，提高了冬油菜氮素含量，改善了群体质量，进而提高了籽粒产量，降低了油菜产量的相对受害率（RIR），其中产量相对受害率随施氮量增加从35.3%下降到13.8%。高氮量（240~300 kg/hm2）水平下各时期干物质量和氮素累积量的下降幅度显著低于中低施氮量（0~180 kg/hm2），其中高氮量水平下平均降幅分别为9.5%和15.0%，而中低氮水平下的平均降幅分别为27.6%和32.9%。一定范围内增施氮肥对苗期渍水后直播冬油菜生长恢复具有很好的补偿效应。在保证产量（2500 kg/hm2）不下降的情况下，排水处理要比渍水处理节省氮肥59.2 kg/hm2。【结论】 苗期渍水胁迫对油菜生长的抑制不仅作用于渍水期，其负面效应同样会延伸至整个生育阶段，最终导致产量损失。施氮可以明显缓解渍害的负面效应，优化冬油菜群体质量，实现高产。因此，合理氮肥用量和实时排水可以达到施氮减渍和排水减氮的双重效果。

Effects of waterlogging at the seedling stage and nitrogen application on seed yields and nitrogen use efficiency of direct-sown winter rapeseed (Brassica napus L.)

[Objectives] The autumn waterlogging is one of the common constraint factors in winter rapeseed production.In this research,a field experiment was carried out to study effects of water logging at the seedling stage and nitrogen (N) application on seed yields and N use efficiency of direct-sown winter rapeseed,to provide a theoretical foundation for reasonable utilization of N fertilizer in direct-sown winter rapeseed under the waterlogging stress.[Methods] The field experiment was conducted by using a local major rapeseed cultivar,Huayouza 9.Direct-sowing was the main cultivation pattern.A split-plot experiment was designed,and the main plots were soil water conditions which consisted drainage treatment and waterlogging treatment at the seeding stage and N application rates were sub-plots at six levels,0,60,120,180,240 and 300 kg/hm2.Growth characteristics,dry matter and N accumulation,and N utilization were studied at the seedling,budding,flowering and maturity stage,meanwhile,the yield and its components were investigated.[Results] The growth of rapeseed and yield were obviously inhibited by waterlodging at seedling stage.Compared with the drainage,waterlogging significantly reduced the number,area and the SPAD values of leaves at different degrees under the same N levels.The dry matter amounts were reduced by 19.1％-26.5％,and the harvest indices were decreased by 5.2 percentage points after the waterlogging.The seed yield was significantly decreased by 23.6％ under the waterlogging stress,and the decreased seed yield resulted from a decrease in density at the five leaf stage and the number of siliques per plant,which were reduced by 7.6％ and 20.4％,respectively.Moreover,the N content of the plants was decreased by 8.0 percentage points,the N accumulation amounts were reduced by 23.2％-32.4％,and the N partial factor productivity (PFPN),N agronomy efficiency (AEN) and N recovery efficiency (REN) were declined by 22.8％,20.4％ and 18.6％ under the waterlogging stress,respectively.Suitable nitrogen application could alleviate the effect of the waterlogging on the growth and yield of winter rapeseed,and there was a direct relationship between the responses of the yield to the waterlogging stress and N input.The N application significantly enhanced leaf number,leaf area and the SPAD value of leaves,increased density,N content,population quality and the yield,reduced the RIR (relative damage percent) of rapeseed yield which declined from 35.3％ to 13.8％ with the increment of N application.The decreases of the dry matter and N accumulation amounts were alleviated by the N application under high N levels range from 240 to 300 kg/hm2 and decreased by 9.5％ and 15.0％,respectively,while they were decreased by 27.6 ％ and 32.9 ％ under the middle or low N levels range from 0 to 180 kg/hm2.Therefore,under a certain amount of N fertilization,increasing the N rate could show compensation effect on direct-sown winter rapeseed growth and recovery.Compared with the waterlogging treatment,59.2 kg/hm2 of N fertilizer was reduced in the drainage treatment.[Conclusions] The inhibiting effect of the waterlogging on rapeseed not only affected the seedling stage,but also impacted other growth stages,and eventually led to the yield loss.The N application could increase the grain yield to alleviate the negative effects by optimize population quality for rapeseed under the waterlogging stress.So,suitable N fertilization rate and real-time drainage would be feasible and realizable with obtaining on both waterlogging resistance by N rate and N reduction by drainage.