Effects of different green manure crops and mulching approaches on wheat yield and soil moisture dynamics in the dryland region

Objectives Green manure (GM) rotation of winter wheat can reduce crop yield in dry years. Here, we explore the effects of combining dryland green manure and film mulching measures on wheat yield and its dynamics of water use efficiency (WUE, 0–200 cm soil depth) in normal and dry years to establish a science-based efficient wheat green manure rotation system.

Methods A short-term field experiment with a split-plot design was conducted in Yongshou County, Shaanxi Province from 2017 to 2019. The main plot was the different GM crops, including the black bean and rapeseed, and summer fallow was the control. The sub-plot was the plastic mulching practices, including conventional tillage (CK), and ridge-mulching and furrow-seeding practices. Data of winter wheat yield and WUE were collected at reviving stage, flowering stage, and harvesting stage.

Results 1) In the normal and dry years, the winter wheat yield in the rapeseed treatment was (P < 0.05) higher than the black bean treatment (9.3% vs. 43.5%). 2) Under the conditions of ridge-mulching and furrow-seeding, planting GM crops (P < 0.05) reduced winter wheat water consumption during the growth period increased its WUE in the normal year. In the normal year, the WUE of wheat in the rapeseed reached the maximum 14.3 kg/(hm²·mm), which was 7.4% higher than fallow. In the dry year, GM crops reduced the WUE of wheat by 58.5% in black bean and 38.3% in rapeseed, compared with fallow. We found a significant (P < 0.05) interaction effect of GM and ridge-mulching and furrow-seeding approaches on winter wheat WUE. 3) Planting GM crops with ridge-mulching and furrow-seeding increased soil moisture consumption. Compared with the summer fallow treatment in the normal and dry years, the soil water storage at a depth of 0–200 cm before sowing winter wheat (P < 0.05) reduced by 10.1% and 15.7%, respectively.

Conclusions Growing rapeseed as a GM crop with ridge-mulching and furrow-seeding improved the WUE of winter wheat without reducing crop yield. However, there was a reduction in wheat yield and WUE in the dry years.