The yield of dryland wheat can be promoted in plastic-film-mulching cultivation but the grain protein content is decreased simultaneously. Fertilizer management is considered as one of the solutions to this problem. From September 2013 to September 2016, we conducted a three-year experiment in four fixed dryland plots in central Loess Plateau with winter wheat under three cropping patterns. The CP pattern was the local conventional cropping pattern without plastic film mulching and uniform fertilization. The RF pattern was carried out by ridge mulching, furrow seeding and uniform fertilization. The RFF pattern was similar to RF except that fertilizer was located with side-dressing under plastic film. The nitrate-N content in 0–40 cm soil layer, soil moisture (0–200 cm), the nitrogen absorption and utilization of wheat plant, final yield, grain protein content, and water use efficiency (WUE) were measured. In the dry 2013–2014 and 2015–2016 growing seasons, compared with CP, yield increased by 9.5% and 6.3% in RF and by 18.8% and 22.8% in RFF, WUE increased by 5.8% and 8.7% in RF and by 13.2% and 19.6% in RFF. The grain protein content under RF condition decreased by 7.1% in 2013–2014 and 9.9% in 2015–2016, however, that under RFF condition had no significant changes in both years. In the wet 2014–2015 growing season, grain yield had no significant changes among CP, RF, and RFF, whereas the grain protein content and WUE in RFF were increased by 6.0% and 17.0%, respectively. RFF could adjust soil water storage and consumption better than RF with decreasing water consumption in 100–200 cm soil layer in wet year and increasing water harvest during fallow period in dry year. In addition, RFF was more favorable than RF to the nitrate-N content in 0–40 cm soil layer, total N content in root at anthesis and harvest, total N content in leaf at anthesis, and N absorption, accumulation in vegetative organs and N translocation to grain. As a result, RFF had higher yield, grain protein content, and WUE than RF. In dry years of 2013–2014 and 2015–2016, compared with RF, the yield in RFF was increased by 8.4% and 15.5%, the grain protein content increased by 9.9% and 8.7%, and WUE increased by 7.0% and 10.0%, respectively. In the wet year of 2014–2015, the grain protein content in RFF was 6.0% higher than that in RF, although there was no significant increase of yield under RFF condition. These results indicate that RFF is an excellent cropping pattern for dryland wheat because it is able to maintain the soil N supply at later growing stage and water storage in deep soil before seeding of the following growing season, as well as increase yield, protein content and WUE of wheat.
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