ObjectiveWater and fertilizer management and water-conserved cultivation have been the research focuses in wheat production of the Northwest China. More attention has concentrated on the yield and water use efficiency and less on nutrient uptakes and efficiencies after the formation of wheat grain yield. So in this paper, effects of different cover measures on N, P and K requirements and physiological efficiencies of winter wheat were studied in dryland of Loess Plateau.

MethodUsing winter wheat as the test crop, continuous field trials were conducted for 4 years in Yongshou County, Shaanxi Province. No nitrogen fertilizer was set as the blank, applying N 195 kg/hm² as control. Other 4 treatments were designed as following: N150 kg/hm² without cover, N150 kg/hm² and film mulching and hole sowing, N150 kg/hm² and ridge mulching and furrow sowing, N150 kg/hm² and straw mulching and hole sowing. Physiological demands and efficiencies of N, P and K for winter wheat grain yields, grain nutrient contents and yield of grain formation were analyzed by measuring the sample plants.

ResultsThe nitrogen requirement of non-covering treatment was 5.3% lower than that of conventional nitrogen application, other indicators had no significant differences. Under the N 150 kg/hm² application conditions, compared with no coverage, the yield of ridge mulching and furrow sowing was not increased, while the aboveground N uptake was increased, and the nitrogen requirement of grain yield was increased by 2.6%, the N physiological efficiency of grain yield was reduced by 6.3%. The yield of film mulching and hole sowing was increased by 6.9%, the aboveground N uptake was increased by11.3%; the yield of straw mulching and hole sowing was increased by 3.5%, the aboveground N uptake was increased by13.2%, and the N requirement of grain yield was increased by 8.5%, the N physiological efficiency of grain yield was reduced by 3.9%. Compared with the treatment of same amount of nitrogen applied without cover, the aboveground P and K uptake of ridge mulching and furrow sowing was not increased, that of film mulching and hole sowing was increased by15.6% and 23.4%, the K physiological efficiency of grain yield was reduced by10.6%; the aboveground P and K uptake of straw mulching and hole sowing was increased by13.2% and 24.4%, the P and K physiological efficiency of grain yield was reduced by 9.9% and 15.1%. After reducing the amount of N applied from 195 kg/hm² to 150 kg/hm², compared with no coverage, using ridge mulching and furrow sowing technology failed to increase wheat yield, but increased the aboveground N uptake, thereby increasing the N requirement of grain yield, reducing the N physiological efficiency. Using the film mulching and hole sowing technology improved the grain yield, increased the aboveground N uptake, therefore did not increase the N requirement of grain yield and the N physiological efficiency. Using straw mulching and hole sowing technology increased grain yield, and increased the aboveground N uptake, the N requirement of grain yield was also increased, thereby reduced the N physiological efficiency.

ConclusionsTherefore, to ensure grain yield and nutrient quality in dryland wheat production, the amount of nitrogen fertilizer should be increased under the plastic mulching and straw mulching.