Effects of rotational tillage practices on soil water characteristics and crop yields in semi-arid areas of north-west China

Winter wheat (Triticum aestivum L.) is a major crop grown generally in semi-arid areas of north-west China, and water deficiency is the major factor that limits crop yields. Between 2007 and 2010, we conducted a field experiment on winter wheat to investigate the effects of interval with no-tillage and subsoiling (rotational tillage) after crop harvesting on soil water characteristics and crop yields in semi-arid areas of southern Ningxia. Three tillage treatments were tested: no-tillage in year 1, subsoiling in year 2, and no-tillage in year 3 (NT/ST/NT); subsoiling in year 1, no-tillage in year 2, and subsoiling in year 3 (ST/NT/ST); and conventional tillage over years 1-3 (CT). The three-year comparative experiment showed that during the summer fallow, compared with CT, the NT/ST/NT and ST/NT/ST treatments improved mean soil water content at 0-2.0m depth by 3.9% and 7.8%, respectively, and significantly (P < 0.05) increased mean rainfall storage efficiency by 15.4% and 26.7%. During the wheat growing season, mean soil water content with the NT/ST/NT and ST/NT/ST treatments was significantly higher (P < 0.05) than with the CT treatment (8.0% and 8.6% higher, respectively), and the two rotational tillage treatments significantly (P < 0.05) increased mean rainfall use efficiency compared with CT (by 9.3% and 10.7%, respectively). Yield improvements coupled with greater water-use efficiency occurred with the NT/ST/NT and ST/NT/ST treatments, i.e. mean grain yields were significantly (P < 0.05) increased by 9.6% and 10.7%, respectively, and water-use efficiency was significantly (P < 0.05) improved by 6.7% and 7.8% compared with the CT treatment. The results showed that the interval of no-tillage and subsoiling could improve soil status, and significantly increase crop yields and water-use efficiency. This method could have important applications in the semi-arid areas of north-west China.