Effects of conservation tillage on soil water regimes and water use efficiency in farmland of Heihe River Basin in Northwest China

Shortage of water resources and extreme drought limit crop production in Heihe River Basin in Northwest China. Those areas are also strongly affected by serious wind erosion, and intensive tillage of conventional agriculture has worsened the situation. Therefore, conventional tillage and four conservation tillage were studied to analyze the effects of different tillage on soil water storage dynamics, soil moisture profile of the key growth periods, grain yield and water use efficiency (WUE) through field experiment implemented in Zhangye from 2003 to 2005. The aim of the research is to identify a suitable conservation agriculture practice for this area. The results showed that the soil water storage of conservation tillage was more than that of the conventional tillage. The sequence of soil water storage in 0 to 30 cm was NPS40>NS40>NS20>NPS20>CT at the end of fallow stage while it was different from sowing to jointing stage as NPS40>NS40>NS20>NPS20>CT in 2004 and NS40>NS20>NPS40>NPS20>CT in 2005. This is as a result of the great influences of tillage measures, rainfall and evaporation. The change of soil water storage was gentle in 30 to 120 cm layer due to the less influences of meteorological factors and the sequence was NS20>NPS20>NPS40>NS40>CT in two years. Soil water content in 0 to 5 cm soil layer of NPS40, NS40, NPS20 and NS20 was increased by 37.29, 37.10, 21.49 and 41.90% in 2004, and 33.99, 40.17, 8.90 and 38.44% in 2005, respectively compared to conventional tillage at sowing time. Conservation tillage changed the soil water supplying characteristic that could supply more water for crop growth and development under the conditions of water storage, while it saved more for coming stage when soil water was sufficient. Conservation tillage increased grain yield and WUE greatly and NPS20 is the most reasonable cropping system in this area, which increased grain yield and WUE by 53.08 and 5.85% in 2004 and 52.04 and by 7.30% in 2005 respectively.