Effects of tillage practices on water consumption and grain yield of dryland winter wheat under different precipitation distribution in the loess plateau of China

Deep ploughing and subsoiling are important management practices used for mitigating the risk of soil compaction under long term no-tillage or reduced tillage practices. These fallow tillage methods have been widely applied in the Loess Plateau region of China to improve soil water availability and preventing soil erosion. To investigate the effect of different tillage practices for increasing the production of winter wheat (Triticum aestivum L.) and their relationship with precipitation distribution in the semiarid southeast region of the Loess Plateau, a six-year field study was conducted from 2009 to 2015, using three tillage treatments: deep ploughing (DP), subsoiling (SS), and no-tillage (NT). Our results indicated that DP and SS treatments increased soil water storage in the 0-300 cm soil layer at sowing and soil organic carbon in the 0-20 cm soil layer at maturity. In addition, DP and SS increased soil water consumption in the 0-180 cm soil layer from sowing to anthesis, and in the 120-300 cm layer from anthesis to maturity of wheat. Furthermore, the DP and SS treatments significantly increased the root length, root surface area, and the number of root tips in the 0-80 cm and aboveground dry biomass at maturity. Additionally, DP and SS treatments increased the grain yield by 31% and 26%, precipitation use efficiency by 32% and 26%, and water use efficiency by 12% and 11% respectively, as compared with those of the NT treatments. Pearson's correlation analysis showed that soil water consumption was significantly positively correlated with precipitation from sowing to jointing and anthesis to maturity. In addition, grain yield had a significant positive correlation with precipitation during the fallow season, particularly in the SS treatment. Moreover, grain yield was significantly positively correlated with soil water consumption in the 0-180 cm soil layer from sowing to jointing, and at 60-240 cm soil depth from jointing to maturity. In conclusion, under low precipitation, DP was more favorable for winter wheat than SS, whereas, under high precipitation, SS was more beneficial than DP.