Yield and N, P and K uptake and utilization of winter
wheat affected by straw return to soil

【Objectives】Guanzhong Plain in Shaanxi province is a typical winter wheat-summer maize rotation region in China, where maize straw returned to soil before winter wheat sowing is one of main crop straw management patterns. In order to increase crop yield and fertilizer utilization efficiency by optimizing nutrient management of winter wheat under the maize straw return to soil, a two-year location-fixed field experiment was carried out to explore the best nutrient management measure for high yield and high efficiency production of winter wheat when the straw was returned to soil in Guanzhong Plain. 【Methods】 The field experiment was initiated in October 2011 and ended in May 2013 at Zhongnan town, Zhouzhi county in Shaanxi province. Local winter wheat cultivar of Zhoumai 23 and summer maize cultivar of Zhengdan 958 were used as test crops. The experiment was arranged in a split block design with two main treatments and five subplots. The main treatments included all the maize straw return to soil (S1) and all straw removal treatment (S0), and the subplots were five N application rates of 0, 84, 168, 252 and 336 kg/hm2 with four replicates. Effects of the maize straw return to soil on grain yield of the following wheat and its nitrogen, phosphorus and potassium (N, P and K) uptake and utilization were studied. 【Results】 The results show that the winter wheat grain yield and the amounts of N, P and K uptake in aboveground part at the maturity stage are decreased when the N rate is low under the straw return, while they are increased under the high N rates, compared with the maize straw removal treatment. The grain yields are decreased under the straw return treatments when the N rates are lower than 153 and 187 kg/hm2, respectively in the first and second year, and the yields are increased when the N rates are higher than them, even with more yield increases under much higher N rates. The response of the biomass to the straw return is the same as the grain yield, and under the same amount of biomass and the maize straw return or removal, the N rates are 190 and 202 kg/hm2 in the first and second year, respectively. Among the wheat yield component factors, grain number per spike and 1000-grain weight are not significantly affected by the straw return under the same N rate, while the spike number per hectare is different, and the increased grain yield under the straw return condition at higher N rate is mainly caused by the enhanced spike number. The amounts of N, P and K uptake in aboveground part of winter wheat are increased by the straw return when the N application rates are higher than 275, 123 and 213 kg/hm2 in the first year and 200, 165 and 241 kg/hm2 in the second year, respectively, but their harvest indexes are not in the increasing tendency under high levels of N rates. Also, the reduction of P concentration in winter wheat grain is found due to over-fertilization of nitrogen.【Conclusions】 Comprehensive consideration of the changes of winter wheat grain yield, N, P and K uptake and their utilization in aboveground part under the same N level and the straw return to soil condition, the N application rates for winter wheat are suggested to be within the range of N 150 to 200 kg/hm2 in the winter wheat-summer maize rotation region of Guanzhong Plain for ensuring higher wheat yield and utilization efficiencies of N, P and K nutrient resource when the maize straw is returned to soil before winter wheat sowing.