Effects Of Different Green Manure And Mulching Approaches On Wheat Yield And Soil Moisture Dynamics In Dryland Condition

Water scarcity and poor soil fertility are the two major obstructions for the sustainable agricultural development in winter wheat agro-ecosystems in the Weibei dryland.Growing the green manure?GM?crops during the summer fallow period is an efficient method to improve soil fertility.However,the negative effects of the GM crops on the winter wheat growth and yield have been found when the rainfall is scarce.In order to resolve this practical problem,a new GM planting system which combined the green manure crops with plastic mulching measures should be explored and evaluated under the dryland condition.A short-term field experiment with a split-plot design was conducted in Yongshou County,Shaanxi Province from 2017 to 2019.The main treatment was the different GM approaches,which included planting the black bean and rapeseed as the GM crops,and summer fallow is the control treatment.The sub-treatment was the plastic mulching practices,which included the conventional tillage?CK?&ridge-mulching and furrow-seeding practices.The purpose of this study is to investigate the effects of different GM varieties and plastic mulching approaches on growth,yield,nutrient uptake and utilization,water use efficiency of winter wheat,soil fertility and soil water balance.The main results were as followed:?1?Among the two GM species,the total dry biomass of black bean was higher than that of rapeseed,however,the amounts of N,P,K accumulation of rapeseed were all higher than those of black bean.GM crops grew vigorously under the ridge-mulching and furrow-seeding approach,as a result the dry biomass was significantly higher than that under conventional tillage.?2?The winter wheat yield in the rapeseed with ridge-mulching and furrow-seeding treatment was greater and more stable than that in the black bean with ridge-mulching and furrow-seeding treatment,with an average increase of 23.5%.In addition,planting the black bean with ridge-mulching and furrow-seeding performed better on the biomass production during its growing period when the annual precipitation was relatively adequate and planting the black bean with ridge-mulching and furrow-seeding performed better when the rainfall was scarce.Planting GM crops with ridge-mulching and furrow-seeding increased the nutrient accumulation of wheat seedling above-ground parts,among which rapeseed performed better,with an average increase of 42.6%,30.0%and 16.3%for the N,P and K accumulations of winter wheat above-ground parts at the greening stage,respectively.In addition,planting GM crops with ridge-mulching and furrow-seeding increased the contribution rates of transferred N and P to the grain,and reduced the loss amounts of transfer K after anthesis and increased the K content in the grain.There was no significant interaction effects between the GM crops and ridge-mulching and furrow-seeding approaches on the winter wheat biomass,yield and nutrient accumulation/transfer.?3?Planting GM crops with ridge-mulching and furrow-seeding could improve the soil fertility.Compared with fallow treatment,black bean and rapeseed increased soil organic matter contents by 10.6%?on average?,but had no significant effects on total N,available P and available K contents.There was no significant interaction effects between the GM crops and ridge-mulching and furrow-seeding on soil fertility.?4?The water consumption of winter wheat during its growth period was significantly reduced by the black bean and rapeseed with ridge-mulching and furrow-seeding approaches.When the annual precipitation was relatively adequate,the water use efficiency?WUE?under rapeseed with ridge-mulching and furrow-seeding treatment was maximum(14.5 kg/hm^2·mm),which was 3%higher than that of fallow.When the annual precipitation was deficit,planting GM crops with ridge-mulching and furrow-seeding treatment reduced the WUE by 45%compared with fallow.Although there was no significant interaction effects between GM crops with ridge-mulching and furrow-seeding on water consumption,there was a significant interaction effect on WUE.Planting GM crops with ridge-mulching and furrow-seeding did not increase the soil water storage,it indeed accelerated the consumption of soil water.Compared with fallow,planting GM crop with ridge-mulching and furrow-seeding reduced the soil water storage of 0-100 cm before winter wheat planting,with an average decrease of13.4%,and reduced the soil water storage of 0-200 cm,with an average decrease of 15.7%when the rainfall was scarce.In conclusion,growing the rapeseed as the GM crops with ridge-mulching and furrow-seeding improved the WUE of winter wheat without reducing the yield,promoted its growth and N,P,K absorptions at the seedling stage,and effectively increased the soil organic matter contents at the depth of 0 to 10 cm.Our study could provide a new idea and technical model to enhance the water and natural resources utilization efficiencies under dry-land conditions,and promoting the development of GM cropping system in China.