Influence on Carbon and Nitrogen Mineralization after Dissolved Organic Matter Removal in Subtropical Chinese Paddy Soils

【Objective】The effects of dissolved organic matter(DOM) were studied on carbon and nitrogen mineralization in subtropical Chinese paddy soils.as The pupose was to provide a firm foundation for better understanding of the mechanisms of C,N cycle,establishing scientific nutrient managements,and regulating greenhouse gas emission in soils.【Method】 Incubation experiments were conducted,and chemical analysis of paddy soils was derived from Quaternary red clay.A comparison with upland red soil was made,and the difference found was in mineralization of soil organic carbon.Nitrogen was investigated between DOM removed soil and the original;【Result】Soil organic C mineralization decreased by 6.3%-8.9% with an average of 7.5% after DOM removed in the first period(12d) and only by 3.6%-6.1% with an average of 5.0% in the whole incubation period.There was not significant difference.The effects of DOM removal on the mineralization of soil organic N were different.The cumulative mineralization of soil organic N in paddy soils after DOM removal decreased significantly(11.2%-18.3%) with an average of 12.9%.Compared with paddy soils,the cumulative mineralization of red soil organic N in upland only decreased by 7.6%.【Conclusion】It was suggested that while being a small proportion of the soil OM,DOM plays a significant role in the transport and supply of nitrogen(N) to microbial population.It is the initial substrate for OM mineralization and considered to be important in the N mineralization.