Sequestration of Straw Carbon in Aggregates of Black Soil with Different Amounts of Straw Addition
[Objective]Returning straw to the field is a reasonable and effective measure to accelerate the utilization of agricultural waste as resources and to increase the storage of soil organic carbon(C).However,the stabilization and transformation process of straw C in different aggregates fractions of Black soils was not very clear.[Method]The 13C-labeled straw treatments(as percentages of 1％,3％,5％and 10％)were added to low and high fertility levels of Black soil,and then they were incubated in-situ for 360 days.This paper analyzed the dynamic changes of organic C of aggregate fractions,and studied the transportation characteristics of native organic C and straw-C in aggregate fractions,in order to reveal the sequestration process of soil organic C.[Result]Compared with the treatment without straw addition,more than 3％of straw addition treatments significantly increased the organic C contents of low and high fertility soils by 21.00％to 81.81％and 12.40％to 44.00％,respectively.Under the high fertility soil,the proportions of macro-aggregate fraction in soil were increased by 10.3 to 21.3％relative to the low fertility soil with the straw addition treatments.At the end of incubation,the average organic C content of macro-aggregate fractions was increased by 11.4％in high fertility soil compared with low fertility soil.Compared with the no straw addition treatment,10％of straw addition significantly increased the content of organic C in soil micro-aggregate fraction in the low and high fertility soils by 36％and 67％,respectively(P＜0.05).The contribution percentage of straw C to total organic C in macro-aggregate fraction was decreased gradually,while that in microaggregate(53～250 pm)and sit and clay fraction(＜53pm)were gradually increased in soils with varied amount of straw addition after 360 days of incubation.[Conclusion]As the straw decomposition,straw C gradually was transported and accumulated from macro-aggregate fraction to smaller size aggregate fractions.The organic C content of silt and clay fraction in high fertility of Black soil tends to be stable with straw addition.After adding straw to high fertility black soil,the organic C content of clay particles tends to be stabilized.
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