Effects of Plastic Film Mulching on Grain Yield and Sulfur Concentration of Winter Wheat in Dryland of Loess Plateau

Plastic film mulching is popular in dryland wheat production in China and important to understand to effects on grain yield, sulfur (S) accumulation and remobilization, and grain S concentration in high-yield and nutritional-quality wheat production. In the 2014–2015 and 2015–2016 growing seasons, we carried out field experiments in seven locations of three provinces in Northwest China to compare the biomass, grain yield, yield components, grain S concentration, and S uptake and distribution of winter wheat between conventional flat cropping pattern (no mulching) and the ridge mulch with furrow seeding or flat mulching cropping pattern (plastic film mulching). Compared with no mulching pattern, the plastic film mulching pattern showed 13.7% increase of grain yield through higher spike number, but 9.0% decrease of grain S concentration. The S accumulation in stem and leaf, ear, and aboveground plant parts at anthesis increased by 19.9%, 16.1%, and 19.2%, respectively, in plastic film mulching pattern than in no mulching pattern; however, the S remobilization amount and efficiency increased by 36.2% and 17.9%, respectively, during grain filling. Under plastic film mulching pattern, soil available S at anthesis stage decreased by 24.5%, and the S uptake during grain filling greatly declined by 77.9%. As a result, no significant increases in S accumulation of aboveground plant parts at maturity and S harvest index. The grain S concentration decreased owing to the increased grain yield. Therefore, under plastic film mulching pattern in Northwest China, additional S fertilizer should be applied for improving S nutrition and processing quality in dryland wheat.