耕作措施对双季稻田土壤碳及有机碳储量的影响

针对不同耕作措施对双季稻田的固碳效应和固碳潜力问题,选择湖南省宁乡县的双季稻区试验点进行了有机碳、活性有机碳以及耕层有机碳储量的研究,以期为制定适合于稻田条件下的合理耕作方式提供理论依据。结果表明,耕作措施和秸秆还田对有机碳（SOC）和活性有机碳（AOC）含量均产生不同程度的影响。免耕处理下,有机碳和活性有机碳含量皆随土壤深度的增加而减少,土壤0～5cm的SOC和AOC的含量最高,且与其他层次达到显著性差异水平（P＆lt;0.05）,具有明显的表层富集现象。与免耕相比,旋耕和翻耕则更利于5～10cm和10～20cm土层的有机碳和活性有机碳的积累。比较秸秆还田对SOC和AOC的影响表明,秸秆还田有效地提高了0～10cm有机碳含量,但对10～20cm并未产生显著影响,秸秆的输入并未增加土壤活性有机碳的含量。采用等质量方法计算了耕层土壤有机碳储量,结果显示旋耕秸秆还田使有机碳储量明显增加,而免耕只增加了土壤0～5cm和5～10cm土层有机碳储量,10～20cm有机碳储量有所降低,但耕作措施对有机碳储量的长效作用还有待于进一步研究。

Effect of Different Tillage on Soil Organic Carbon and the Organic Carbon Storage in Two-crop Paddy Field

Soil organic carbon sequestration influence agroecosystem suitability and affects global wanning, more and more is concerned by people now. Tillage not only affects soil organic carbon contents but also influence the components of SOC. In order to solve the problem of carbon sequestration that occurred in the double rice paddy field, four tillage practices were conducted from 2005 in Ningxiang County, the double rice paddy Hunan Province. Tillage practices included conventional tillage, rotary tillage and no tillage. Rice stubble was returned in conventional tillage （CTS）, rotary tillage （RTS） and no tillage （NTS）, 12 500 kg. bm-2. Conventional tillage also includes plow tillage without stubble returned（CT）. The tillage methods were the same of early rice and late flee. The total organic carbon （TOC）, active organic carbon （AOC） and soil organic carbon storage were discussed in this paper with data of 2007. The results indicated that TOC and AOC were decreased with the depth of soil layer. The stratification ratios（SR） of TOC and AOC were increased significantly under no-tillage than that under minimum tillage and moldboard plow tillage at the 5% level. The storage of SOC and TOC at the 5-20 cm soil layer was enhanced un- der CTS and RTS compared to NTS. Straw returned could inerease SOC storage in the 0-10 cm layer effectively, but no signifieant effect was found in the 10-20 cm soil layer. Furthermore, stubble returned had not significant effect on AOC under moldboard plow tillage. Rotary tillage had a great improvement on the storage of SOC, while, No-tillage increased SOC storage in the layer of 0-10 cm and reduced in the 10-20 cm layer by using the method of equivalent soil mass.