关键词: 黄土高原, 旱地小麦, 覆膜栽培, 产量形成, 氮素利用

Abstract: 【Objective】The objective of the study was to determine the effects of film mulching cultivation on yield formation and nitrogen uptake-translocation of winter wheat in dry highland of Loess Plateau, so as to provide important basis for high yield and high efficiency in rainfed winter wheat production.【Method】An experiment was conducted to study the effects of interactions between different fertilization and film mulching practices on yield formation of winter wheat, aboveground nitrogen accumulation and translocation, soil nitrate-N residue and N balance in soil-plant system by four cultivation patterns, including farmer pattern (PF), farmer fertilization rate plus ridge mulching-furrow planting (RFSF1), monitoring fertilization plus ridge mulching-furrow planting (RFSF2) and monitoring fertilization plus whole field filming with soil covering and hole-seeding (WFFHS), during 2012-2016 in winter wheat growing region of dry highland in Southern Shanxi. 【Result】 Obtained results showed that average yield of winter wheat under traditional farmer pattern was 3 367 kg·hm^-2 , which could be increased to 4 491 kg·hm^-2 by optimized fertilization combined with mulching cultivation. The contribution rate of optimized fertilization on yield was 14.8%, and the synergy contribution rate of mulching and optimized fertilization was up to 24.7%-42.1%. The yield formation mainly depended on spike number per hectare, followed by thousand kernel weight in dry high land of Loess Plateau. Due to the reasonable population construction and favorable water and nutrient conditions, the spike number per hectare, 1000-grain weight and yield of WFFHS treatment were the highest, with the mean value of 5.81million·hm^-2, 44.3 g and 4 785 kg·hm^-2, respectively. In terms of aboveground nitrogen translocation, a significant positive correlation was observed between nitrogen translocation amount from vegetative organs to grains after anthesis and biomass or grain yield, the correlation coefficients were 0.959** and 0.960**, respectively. About three quarters of N in grain were from translocation of vegetative organs before anthesis, and a quarter from root uptake after anthesis under the PF treatment, optimized fertilization combined with mulching cultivation remarkably increased the nitrogen translocation amount from vegetative organs to grains, the translocation contribution rate was 81.4%-88.8%. In terms of soil nitrate-N residue, the accumulation amounts of nitrate nitrogen of 1 m soil layer had been over 100 kg·hm^-2 on account of long-term excessive fertilization in Loess Plateau, and the peak of nitrate nitrogen accumulation was 20-60 cm layer. After successive planting of winter wheat for 4 years, the accumulation amounts of nitrate nitrogen in 2 m soil layer under traditional fertilization rate had been up to 277 kg·hm^-2, of which 75% concentrated on 0-120 cm soil layer, with a 87.7% increase since pre-sowing of 2012. However, the amounts of nitrate nitrogen accumulation in 2 m soil layer under optimized fertilization combined with mulching cultivation was only 15.7%-24.2% higher than that at pre-sowing in 2012. Meanwhile, it was found that nitrate nitrogen accumulation in 120-200 cm at harvest stage in 2016 was 10.2%-133.7% higher than that at pre-sowing in 2012, which indicated that the residual nitrate nitrogen had a strong leaching downward trend. With considering of aftereffect of residual N, the soil N balance for 4 years was overall analyzed, and it was observed that the N utilization efficiency was 28.8%-56.7%, the N apparent residual rate was 12.1%-28.9%, and the N apparent loss rate was 31.2%-49.6% in dry highland of Loess Plateau. Optimized fertilization combined with mulching cultivation could reduce the apparent nitrogen loss and the residual Nmin, increase the apparent mineralized nitrogen. The WFFHS treatment could utilize the residual Nmin and mineralized nitrogen in a more great extent, which accumulated in the previous years, so the WFFHS treatment had lowest nitrogen apparent loss rate (31.2%) and N apparent residual rate (12.1%), highest N utilization efficiency (56.7%) among all the treatments.【Conclusion】it was concluded that whole field filming with soil covering and hole-seeding combined with monitoring fertilization cultivation could further improve the soil water and fertilizer condition, utilize the residual Nmin, increase the aboveground nitrogen accumulation and translocation, construct reasonable population, and obtain the remarkable yield increasing effect and higher N utilization efficiency finally. So it was considered as a recommendable cultivation mode in dryland of Loess Plateau.

Key words: Loess Plateau, rain-fed wheat, film mulching cultivation, yield formation, nitrogen utilization