Effects of long-term conservation tillage on soil organic carbon,maize yield and water utilization

【Objectives】 Conservation tillage is widely used in dry farmlands of northern China in recent years. A long term field experiment (2003-2013) was conducted to explore impact of the conservation tillage on soil organic carbon (SOC), spring maize yield and water utilization. We demonstrated the cause of yield improvement in the conservation tillage further, and then provided theoretical and technical support for dry farmland tillage. 【Methods】 There were three treatments, conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). Annual variations of SOC (0-20 cm and 20-40 cm), soil moisture at 20 cm depth, crop water consumption, maize yield and water use efficiency were analyzed, and effect of the three tillage methods on above factors was also analyzed. Correlation analysis between maize yield and above factors was done in our study. 【Results】 1) The conservation tillage can improve soil organic carbon (SOC) content, the annual SOC (0-20 cm) contents of the RT and NT treatments were increased by 11.2% and 3.4% compared with CT respectively, and the SOC (20-40 cm) of the RT and NT treatment were increased 5.53 and 3.29 g/kg. The increased rates of 0-20cm SOC stock of RT and NT were C 0.365 and 0.754 t/(hm2a) respectively. 2) The conservation tillage significantly increased crop yields: the average annual yields of 2003-2013 of the RT and NT treatments were 5.83 t/hm2 and 5.39 t/hm2 respectively, which are 14.7% and 6.1% higher than that of CT. 3) The maize yield under the tillage had significant quadratic relationship with the soil 0-20 cm layer water content, and had significant power equation relationship with crop water consumption. 4) The conservation tillage can increase soil moisture, reduce water consumption during maize growth and improve water use efficiency (WUE): compared with the CT and RT, NT increased the average moisture contents of 2003-2013 by 1.90 and 1.66 percentage points, whereas decreased annual water consumption by 16.1 mm and 7.6 mm; compared with CT, RT and NT increased WUEs by 16.1% and 10.2%, and precipitation use efficiencies (PUE) by 13.9% and 5.8% respectively. 【Conclusions】 The long-term conservation tillage can improve SOC and soil water content and decrease useless water consumption effectively, thus improve yield and water use efficiency. RT has the best performance, followed by NT. In general, promotion of conservation tillage is an effective way for increasing yield and water conservation in dry farmlands.