Restricted mineralization of fresh organic materials incorporated into a subtropical paddy soil
Wu J, Zhou P, Li L, Su Y, Yuan H, Syers JK
Key Laboratory of Agro-ecological Processes in the Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Changsha, China.
Abstract
BACKGROUND:
Microbial activities involved in the dynamics of organic matter determine the potential for organic carbon (C) accumulation in soil. To understand this for paddy soil, an incubation experiment (25 °C, 45% water-holding capacity) was established using (14)C-labelled glucose and rice straw (500 µg C g(-1) soil) as substrates; an adjacent upland soil was used for comparison.
RESULTS:
The amount of microbial biomass in the paddy soil was approximately 6 times larger and its turnover rate was 1.5-3 times faster than in the upland soil. These proportions of (14)C-labelled glucose and rice straw mineralized in the paddy soil were about 3% smaller (P < 0.01) than those in the upland soil. Also, there was no significant priming effect of fresh substrate additions on the mineralization of native organic C in the paddy soil, while the priming effect was significant in the upland soil.
CONCLUSION:
Although the paddy soil contains a large amount of microbial biomass, which is also very active, the mineralization of fresh substrates is significantly restricted in this soil, along with a small priming effect. This favours the accumulation of organic C in paddy soils.
Keywords:organic matter determine the potential for organic carbon (C) accumulation in soil,substrates; an adjacent upland soil was used for comparison.
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