Effects of topdressing nitrogen and plastic film mulched ridge–sowing furrow cultivation on nitrogen utilization of winter wheat on rainfed lands in Southern Shanxi

Nitrogen application amount and time directly affect its uptake, accumulation and translocation in winter wheat, and furthermore affect the yield formation. Too much nitrogen fertilizer would result in low nitrogen use efficiency, high production costs and environmental pollution. Water deficit is the major restriction factor for improving nitrogen utilization efficiency in rainfed lands. Therefore, it is of great importance to apply N fertilizer and match cultivation measure rationally for increasing winter wheat yield and developing environmentfriendly agricultural production in the lands. A field experiment located in rainfed growing areas in Xiangfen county, Shanxi province, was conducted to study the effects of topdressing nitrogen and plastic film mulched ridgesowing furrow cultivation on the nitrogen accumulation rate in the aboveground part of wheat, the soil residual Nmin, apparent N losses, N recovery and N balance in 0 to 2 m soil profile during the two years field experiment period. The results show that the N accumulation rates in wheat and N fertilizer use efficiencies under both the plastic film mulched ridgesowing furrow cultivation and top dressing treatments are increased significantly. The two uptake peaks of nitrogen of winter wheat are at seedling stage and from the revival to heading stages under different treatments, which account for 20%-46% and 29%-57% of the total uptake respectively. The nitrogen use efficiency of top dressing is significantly higher than that of the base fertilization. The amount of soil residual Nmin is increased with the increase of the nitrogen application amount, which is mostly distributed in 0 to 60 cm soil layer, and the peak of NO-3-N accumulation is in 20-40 cm layer. The plastic film mulched ridgesowing furrow cultivation could reduce the residual Nmin, and increase the amount of N apparent loss. The apparent loss of nitrogen is the main pattern of soil N output in wheat growing season, the apparent loss of nitrogen fertilizer rate is from 4087% to 7629%, and mainly occurs from the sowing to revival stages. Under the experiment conditions, with considering of the N accumulation rate, the soil residual Nmin, N recovery and N balance, a planting pattern of postponing N to topdress in the soil thawing period and matching the plastic film mulched ridgesowing furrow cultivation should be taken on winter wheat in rainfed lands.