Abstract:

【Objective】 In order to understand the mechanisms of N transformation and manage N fertilization better, the effect of glucose addition on N transformation in paddy soils with a gradient of organic C content were determined. 【Method】 Changes of mineralization, nitrification and denitrification in paddy soils, as well as their response to glucose addition were measured by incubation experiment. 【Result】 Intensity of mineralization and denitrification were: soils with high fertility ＞ soils with middle fertility ＞ soils with low fertility. During the first week of incubation, net mineralization and denitrification rate in paddy soils with high fertility were 1.9 and 1.1 times of that in soil with middle fertility and 5.3 and 2.9 times of that in soils with low fertility, respectively. Addition of glucose decreased approx. 78.8%, 109.2%, and 177.4% of net mineralization in soils with high, middle, and low fertility, respectively. However, denitrification rate in soils with middle and low fertility increased by 14.4% and 166.2%. The highest nitrate content in all the tested soils was 0.62 mg•kg-1 and the highest nitrification ratio was 0.33%. Addition of glucose had no obvious effects on nitrate content and nitrification ratio. 【Conclusion】 It was suggested that the intensity of mineralization and denitrification were quite different in soils with different fertility. The intensity was increased with the increase of soil organic C content. Addition of glucose decreased mineralization, but increased denitrification. The effects of glucose addition were significantly different in different soils. The effect of glucose addition on soils with low organic C content were greater than that on soils with high organic C content. Neither addition of glucose nor inherent soil organic C had obvious effects on nitrification of test paddy soils.

Key words: paddy soils of subtropical China')">paddy soils of subtropical China, soil fertility, glucose addition, nitrogen transformation