氮肥减施对油菜产量、氮素吸收与利用的影响

Effects of reducing nitrogen application on yield,nitrogen absorption and utilization of oilseed rape

控释尿素的应用是氮肥减施的关键技术之一。明确普通尿素与控释尿素减量施用对油菜产量、氮素吸收与利用的影响,为油菜产业绿色发展中的氮肥管理策略提供参考。本研究从2007~2013年度连续6年在长江中游油菜主产区,开展普通尿素和控释尿素不同用量的田间定位试验,共设置7个处理:不施氮(CK)、普通尿素减氮50%(U-50%)、普通尿素减氮30%(U-30%)、普通尿素全量施用(U)、控释尿素减氮50%(CRU-50%)、控释尿素减氮30%(CRU-30%)和控释尿素全量施用(CRU),研究油菜生长、产量与构成、氮素吸收量与利用对普通尿素和控释尿素减量施用的响应与差异。氮肥施用明显改善了油菜的生长状况,全量施用时,普通尿素和控释尿素之间主要以分枝数存在显著差异;当氮肥减施达到50%时,各生长指标降幅达到显著水平。氮肥全量施用时,控释尿素处理平均产量达到2513 kg/hm^2,与普通尿素之间的相对产量差为6.9%,且随着氮肥的减量施用,两种氮肥之间的产量差逐渐增大。氮肥施用对油菜单株角果数的改变是引起产量差异的主要原因,而每角粒数和千粒重均保持在较为稳定的水平。随着氮肥用量的降低,油菜氮素吸收量呈现显著下降的趋势,最低为不施氮处理(38.2 kg/hm^2);而在同一氮素供应条件下,控释尿素比普通尿素表现出更强的氮素吸收能力。导致控释尿素不同用量间氮素回收效率差异较小(平均变幅为58.2%~66.0%),且高于普通尿素处理。在目前油菜推荐氮肥用量(180 kg/hm^2)的基础上,对于中低土壤供氮田块,普通尿素减量施用可能会引起植株氮素吸收不足和减产的风险,而控释尿素减量30%可维持油菜籽产量和氮肥效率在较高的水平。

The application of controlled-release urea is one of the key technologies in reducing nitrogen(N)fertilization.This study focused on the effects of reducing N on rapeseed yield,nitrogen absorption and utilization,so that to provide reference to N management in green development of rapeseed production.A six-year field experiment from 2007 to 2013 was conducted in the middle reach of the Yangtze River Basin,including seven treatments:(1)CK,no N fertilizer;(2)U-50%,reduced conventional urea by 50%;(3)U-30%,reduced conventional urea by 30%;(4)U,full dose conventional urea;(5)CRU-50%,reduced controlled-release urea by 50%;(6)CRU-30%,reduced controlled-release urea by 30%;(7)CRU,full dose controlled-release urea.The continuous study analyzed the growth,yield and its components,N uptake and use efficiency of oilseed rape and their differences between thetwo types of N fertilizer.The growth of oilseed rape was obviously improved by the application of N fertilizer.The most significant difference was branch number at maturity stage between the full dose U and CRU.The growth indicators showed different ranges of decline with the reducing of N fertilizer,and reached a significant level when N fertilizer reduced at 50%.Rapeseed yield of CRU with the full dose of N fertilizer reached 2513 kg/hm^2.The relative yield gap between U and CRU was 6.9%,and showed an increase trend with the reducing of N fertilizer.The changes of pod number were the main cause of yield difference,since both of the seed number and seed weigh remain at a relatively stable level.The N uptake was decreased by the reducing of N fertilizer,and the CK treatment had the lowest value(38.2 kg/hm^2).CRU showed a greater N absorption capacity than U at the same N fertilizer supply,which resulted in the N recovery efficiency having a slight difference among the different N fertilizer rate(ranged from 58.2%to 66.0%).On the basis of the present recommended N application rate(180 kg/hm^2),reducing conventional urea may cause nutrient uptake shortage and yield loss,but reducing controlled-release urea within 30%could maintain relatively stable yield level in the low or medium level of soil nitrogen supply.