轮耕对双季稻田土壤结构及水贮量的影响

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

该文针对南方稻田长期免耕存在的耕层变浅、下层土壤紧实等问题,进行了土壤轮耕效应的研究。试验选择双季稻区连续7a免耕稻田,2006年4月设置免耕、翻耕和旋耕3种耕作处理。2007年4月将翻耕、旋耕稻田一半免耕,剩下一半继续翻耕、旋耕。每年早稻和晚稻采用同一耕作措施。研究结果表明,长期免耕表层0～5cm土壤体积质量呈降低趋势,而下层10～20cm呈增加趋势。翻耕、旋耕相对于长期免耕能够有效降低下层土壤体积质量,同时,提高下层毛管孔隙度。翻耕、旋耕后免耕下层土壤体积质量呈增加趋势,而毛管孔隙度呈降低趋势。长期免耕后,翻耕、旋耕能够有效增加耕层(0～20cm)土壤水贮量,特别是在土壤含水率偏低时尤为显著,2007年翻耕、旋耕较长期免耕分别高了12.9%和20.7%,而翻耕、旋耕后免耕呈降低趋势。研究还显示,各轮耕耕层土壤质量含水率与体积质量呈显著线性负相关,与毛管孔隙度呈显著线性正相关。总之,长期免耕后,翻耕、旋耕措施通过改变耕层土壤结构,进而提高稻田土壤水贮量。

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.