秸秆还田下减量施氮对作物产量及养分吸收利用的影响

秸秆还田条件下，采用多年田间定位试验研究了N肥减量施用对作物产量、养分吸收利用以及土壤表观N平衡的影响，旨在为关中小麦／玉米一年二熟轮作区合理施用N肥提供依据。结果表明：与常规施N处理（玉米季施氮187．5 kg·hm－2，小麦季施氮150 kg·hm－2）相比，2008—2011年三年中，15％减N、30％减N两个处理均未显著降低作物籽粒与秸秆产量；2010—2011年生长季中，15％减N处理降低了作物秸秆N、P、K周年总吸收量，增加了籽粒N、P、K周年总吸收量，其中籽粒P周年总吸收量增加达显著性水平；30％减N处理显著降低了籽粒N和秸秆N、K周年总吸收量，降幅分别为12．9％、41．9％、18．5％，在小麦收获后，30％减N处理的N素盈余量只有11．3 kg·hm－2，有潜在缺N危险。综合考虑产量、养分吸收利用及土壤表观N平衡，在秸秆还田条件下，15％减N处理的施N量（即玉米季施氮159 kg·hm－2，小麦季施氮127．5 kg·hm－2）为本地区最佳N肥用量。

Effects of reducing nitrogen application on crop yields, nutrients uptake and utilization with straw incorporation

The long term field experiment on N fertilizer reduction under the conditions of straw incorporation was conducted to identify a suitable N rate and provide the theoretical basis of reasonable fertilization for the farmland in wheat-straw cropping system on Guanzhong Plain. Three treatments, conventional applied N, 15% and 30% reduction applied N, were performed by a randomized complete block design with three replications. The results showed that, in comparison with conventional N application treatment, averaged across three years from 2008 to 2011, N reduction by 15% and 30% did not significantly reduce crop grain and straw yields. During the crop growing seasons from 2010 to 2011, N reduction by 15% reduced straw N, P, K annual uptake and increased grain N, P, K annual uptake, especially for grain P uptake. N reduction by 30% significantly reduced grain N, straw N, K annual total uptake by 12.9%, 41.9%, 18.5% respectively. 30% N reduction treatment had the lowest N surplus after harvesting wheat and maize, the N surplus was only 11.3 kg·hm^-2 when wheat was harvested, partially associated with a shortage of N. Taking into account into consideration of the yield, nutrients uptake and utilization, apparent soil N balance, the 15% N reduction treatment has an optimum N application rate (wheat season 127.5 kg·hm^-2, maize season 159.4 kg·hm^-2) in this region.