中文摘要：

针对目前农业生产中存在的施肥增产效应下降问题,研究了磷肥用量对冬小麦养分、氮磷钾和干物质积累及产量的影响,以期为高产高效施肥提供依据。在黄土高原旱地进行田间试验,设不施磷,施磷P2O550kg/hm^2（不足）、P2O5100 kg/hm^2（适量）和P2O5150 kg/hm^2（高量）4个水平,在不同生长期采样测定冬小麦植株生物量、水分及氮磷钾养分含量。结果表明,生物量提高是适量施磷冬小麦籽粒产量增加的主要原因;适量施磷和高量施磷时,生长后期的水分损失分别为植株最大累积量的82%和86%、氮素损失占26%和34%、磷素占2%和13%、钾素占56%和60%。可见,高量施磷使生长后期作物的生物量、水分、氮磷钾养分损失增加,从而导致了冬小麦产量降低,施肥增产效应降低。

英文摘要：

In order to explain the phenomenon of the decrease of crop yield-increasing effects caused by over fertilizer application commonly existing in present agricultural production in China,this paper focused on the effects of P rates on N,P,K and dry matter accumulation and grain yield of winter wheat.A field experiment was carried out with winter wheat as test crop and at P rates of 0,50（deficient）,100（optimum） and 150（excessive） P2O5 kg/hm^2.The aboveground part of the crop was sampled at different stages to estimate the crop biomass and to determine the content of water,N,P and K in different plant parts.Furthermore,the relationship between grain yield and biomass accumulation,water and nutrient uptake in the plant was discussed.The obtained results showed that no significant difference was found for the harvest indexes over different P rates.One of the main reasons for the increase of grain yield caused by optimum P rates was owing to the increased biomass accumulation,but not the increased translocation of dry matter from vegetative part to grain at late growth stages.Excessive P application was observed to increase dry matter losses during late growth stages at 8 364 kg/hm^2,which accounted for 39% of maximum biomass accumulation and was 22% higher than that at optimum P application.The water accumulation rate at rejoining stage was 989 kg/（hm2·d） at optimum P rates,while is 902 kg/（hm2·d） at excessive P rate.However,water loss was 86% of maximum water accumulation at excessive P rates,which was 82% at optimum P rates during the late growth stages.Application of P promoted nutrient uptake at early growth stages,but also increased the nutrient losses at late growth stages with the increase of P rates.Compared to the maximum nutrient accumulation,the losses were 26% and 34% for N,2% and 13% for P,and 26% and 34% for K,respectively at optimum and excessive P application.Excessive P application could not only decrease water accumulation at early growth stages,but also increase the losses of bio