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 14C-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 14C-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. Copyright © 2011 Society of Chemical Industry