Effects of rotational tillage treatments on soil structure and water storage in double rice cropping region

No-tillage (NT) is commonly used in paddy soil of southern China. However, the long-term NT has caused major problems of weed control, subsurface compaction, and so on, which are not beneficial for paddy rice growth. In order to solve these problems, field experiments of rotational tillage operations were set up in double rice cropping region in Hunan province, China. Compared with continuous NT, conventional tillage (CT) and rotary tillage (RT) were conducted in the paddy field under no-tillage for seven years in April, 2006. Then, one-half of the CT plot was converted to new NT, while the remaining half was left intact as continuous CT. Similarly, one-half of the RT plot was converted to new NT, while the remaining half was left intact as continuous RT in April, 2007. Hence, rotational tillage treatments were present each year on all five tillage treatments (NT-NT, CT-CT, CT-NT, RT-RT, and RT-NT). The same tillage methods were used for early and late rice. Results were showed as follow: Lower bulk density and higher capillary porosity of subsurface soil were measured under CT and RT practices compared with long-term NT soil. In contrast, bulk density of the surface soil tended to decrease with long-term NT. Furthermore, higher bulk density and lower capillary porosity of subsurface soil were observed under CT-NT or RT-NT compared with continuous CT or RT treatments, respectively. The field experiments clearly demonstrated that higher water storage of the arable soil layer was found under CT and RT practices compared long-term NT, especially for the lower water content of paddy soil. Compared with long-term NT, the means of water storage in the 0-20 cm soil layer increased with CT and RT by 12.9% and 20.7% in Oct-2007, respectively. Furthermore, the water storage tended to decrease with CT-NT or RT-NT compared with continuous CT or RT treatments, respectively. In addition, the significant negative linear correlation relationships between soil water content and bulk density, and positive linear correlation relationships between soil water content and capillary porosity were observed under rotational tillage treatments on the paddy soil. In all, CT and RT practices could improve the value of water storage of paddy soil by changing soil structure under long-term NT system.