轮耕对双季稻田耕层土壤有机碳储量的影响

【目的】针对南方稻田连续免耕存在的有机碳表层富集现象,进行土壤轮耕效应的初步研究。【方法】试验选择双季稻区连续免耕7年稻田,研究了轮耕对耕层土壤有机碳含量及其对等质量法计算的耕层土壤有机碳储量影响。【结果】长期免耕后,翻耕、旋耕降低了表层0—5cm土壤有机碳含量,提高了下层5—20cm土壤有机碳含量,进而降低了耕层土壤有机碳层化率;而翻耕、旋耕后免耕土壤有机碳含量相对于翻耕、旋耕分别呈相反的趋势。2006—2009年表层600Mg·hm-2土壤有机碳储量均以长期免耕最高。长期免耕后,翻耕、旋耕秸秆还田会提高下层土壤有机碳储量,进而在一定程度上影响耕层2550Mg·hm-2土壤有机碳的累积;而翻耕、旋耕后免耕耕层土壤有机碳储量较翻耕、旋耕有所降低。【结论】长期免耕后,连续免耕秸秆还田会增加表层600Mg·hm-2土壤有机碳储量;而翻耕、旋耕秸秆还田会提高下层土壤有机碳储量。

Effects of Rotational Tillage in Double Rice Cropping Region on Organic Carbon Storage of the Arable Paddy Soil

【Objective】 Accumulation of soil organic carbon (SOC) in surface soil is very common in long-term no-tillage (NT) treatment in southern China. In order to solve this problem, rotational tillage was introduced in this study. 【Method】Field experiments of rotational tillage operations were set up in paddy field with no-tillage for seven years in double rice cropping region in Hunan province, China. SOC and organic carbon storage of equivalent soil mass were discussed under rotational tillage treatments. 【Result】 Compared with long-term NT, higher organic carbon of the subsurface soil, lower organic carbon of the surface soil, and lower carbon stratification ratio of the arable layer were found in CT and RT treatments. Furthermore, higher organic carbon of surface soil and lower organic carbon of subsurface soil were observed in new-NT after one year of CT or RT compared with CT or RT treatments, respectively. Results of field experiment clearly demonstrated that highest organic carbon storage of 600 Mg•hm-2 soil was found in long-term NT treatment, and higher organic carbon storage of the subsurface paddy soil was observed in CT and RT treatments in 2006-2009. And the organic carbon storage of 2 550 Mg•hm-2 soil was affected by CT or RT with late rice straw to field in long-term NT treatment. While the organic carbon storage of the arable paddy soil of new-NT after one year of CT or RT practices tended to decrease compared with CT or RT treatments, respectively. 【Conclusion】 Higher organic carbon storage of 600 Mg•hm-2 soil was observed in long-term NT system. While greater organic carbon storage of subsurface soil tended to increase in CT and RT treatments with late rice straw returning to field in long-term NT system.