耕作措施对长期免耕双季稻田土壤碳库的影响

针对南方稻田长期免耕存在的主要问题,本研究选择湖南省双季稻区连续7年免耕稻田,进行了不同耕作措施对土壤的总有机碳、活性有机碳的变化情况及其对土壤碳库影响的研究,以期为建立合理的轮耕周期提供理论依据。结果表明:0~20 cm平均总有机碳和活性有机碳含量均为旋耕>连续免耕>翻耕。与连续免耕相比,旋耕有利于提高土壤活性有机碳含量(比连续免耕提高了5.08%),翻耕则会促进土壤活性有机碳分解(比连续免耕降低了2.73%)。晚稻收获时0~20 cm平均碳库管理指数也表现为旋耕>连续免耕>翻耕,其中翻耕使碳库管理指数整体上显著降低(比连续免耕降低了21.7%);旋耕略有提高(比连续免耕提高了3.9%),但未达到显著水平(P<0.05)。总之,与连续免耕相比,翻耕可促进土壤活性有机碳分解,进而显著降低碳库管理指数;但旋耕差异不显著(P<0.05)。

Effects of tillage on the carbon pool of paddy soil with long-term no-tillage

In order to solve problems that were occurred for paddy fields with long-term no-tillage,which was not favorable for paddy rice growth,three treatments of no-tillage(NT),rotary tillage(RT),and conventional tillage(CT) were set up in the paddy field with 7 years no-tillage in double cropping rice region,Hunan province.Double rice cropping was practiced annually in this area.Total organic carbon(TOC),active carbon(AC) and carbon pool management index(CPMI) were measured.The results showed that Both TOC and AC in 0 to(20?cm) soil were in the order of RT>NT>CT.Compared with NT,RT enhanced AC.In contrary,CT reduced AC.The average CPMI of 0 to(20?cm) soil was also in the order of RT>NT>CT at the late rice harvest.The CPMI was significantly lower under CT compared to NT,but it was not significant for RT that for NT at the 5% level.In conclusion,compared with NT,CT reduced AC and CPMI.But RT had not significant effect on soil C pool.