Comparative Study of Aggregate Stability and Organic Carbon Fraction in Two Types of Paddy Soils under Tobacco-rice Rotation in Central Hunan
To reveal the difference in the stability of soil aggregates and the effect of organic carbon in two typical paddy soils with the farming mode of tobacco-rice rotation,the distribution and stability of soil aggregates,the content of organic carbon components and their relationships in two typical paddy soils were studied,sampled from the field of tobacco-rice rotation region in central Hunan Province.The results showed that the content of＞0.25 mm aggregates,mean weight diameter of aggregates(MWD)and geometric mean diameter(GMD)of red paddy soil(RPS)were higher than those of purple paddy soil(PPS),but its fractal dimension(D)was lower,indicating that soil structure and aggregate stability of RPS was better than those of PPS;meanwhile,content of total organic carbon(TOC)and particulate organic carbon(POC)in RPS was significantly higher than those in PPS,but there was no significant difference in content of easily oxidized organic carbon(EOC)between RPS and PPS;the MWD and GMD of RPS and PPS were significantly positively correlated with TOC,EOC and POC,while D showed significant negative correlation;although the content of＞0.25 mm aggregates in two types of soil were significantly positively correlated with TOC,EOC and POC,but the influence of organic carbon on＞0.25 mm aggregates of RPS was greater than those of PPS.Meanwhile,the influence of POC on＞0.25 mm aggregates in two types of soil was greater than that of EOC.To cultivate aggregates and improve structure of RPS and PPS with the farming mode of tobacco-rice rotation,the content of soil organic carbon and its fractions should be increased.
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