Long-term evaluation of tillage methods in fallow season for soil water storage, wheat yield and water use efficiency in semiarid southeast of the Loess Plateau

methods: including deep ploughing, subsoiling and no-tillage. Our results indicated that compared to no-tillage, the soil water storage (0-300 cm depth) was averagely increased by 7.8% and 6.0% during fallow season, 13.7% and 9.8% in growing season under deep ploughing and subsoiling respectively. Furthermore, the increasing magnitude in soil water due to deep ploughing and subsoiling was, on average, 10.1% and 5.5% higher in dry season than that in wet one. Improved soil water condition under deep ploughing and subsoiling significantly increased the ear number and grain yield by 20.2% and 15.9%, 30.8% and 25.8% respectively, but did not affect seed number and weight of thousand seed over the experimental seasons. Moreover, grain yields under deep ploughing and subsoiling were averagely increased by 35.2% and 24.8% in dry season, 28.7% and 20.6% in wet season respectively. Accordingly, water use efficiency and precipitation use efficiency were increased by 12.1% and 31.9% under deep ploughing, 11.1% and 25.0% under subsoiling respectively. Critically, we found that with an increase of 10% water storage efficiency during fallow season, ear number, grain yield and WUE could be increased by 0.2 million ha−1, 241.1 kg ha−1 and 0.6 kg ha−1 mm−1 respectively. Our study clearly indicated that deep ploughing in fallow season should be adopted as a promising strategy to retain soil water availability and hence boost wheat productivity in semiarid southeast Loess Plateau.