Effect of nitrogen and phosphorus fertilization rate on yield and nitrogen utilization of winter wheat in dryland of Loess Plateau

Based on long term positioned fertilization experiment of rainfed farmland ecosystem in the Middle and South Loess Plateau, effect of nitrogen rate and phosphorus rate on crop yield, nitrogen absorption and utilization in two precipitation-type years were researched by selecting ten treatments. Crop yield increased rapidly with increasing nitrogen in the range of 0-45 kg/hm2 during average year and 0-90 kg/hm2 during dry year, while there were little difference out of this range. In the range of 0-45 kg/hm2 crop yield could be improved rapidly but phosphorus application reduced harvesting index in dry year. Nitrogen absorptions by crop had a similar tendency with yields while nitrogen and phosphorus application changing. Nitrogen harvesting indexes under different nitrogen rates had no significant difference in both precipitation years, but increased with increasing phosphorus rates in dry year and had no significant difference in average year. Nitrogen utilization efficiency (NUE) decreased with increasing nitrogen rates in average year while there was no significant difference in dry year among nitrogen rate treatments. Phosphorus application improved NUE while little difference to higher phosphorus rate treatments. Yield had a significant relationship with nitrogen absorption which was expressed to quadratic curve and hence NUE decreased with nitrogen absorption to linear curve in dry year. Nitrogen and phosphorus application combined with temperate rate were important for ensuring higher nitrogen absorption and NUE , at the same time, higher yield could be obtained and preventing drought ability of winter wheat could be stronger for in dryland on the Loess Plateau.