Restricted mineralization of fresh organic materials incorporated into a subtropical paddy soil

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 degrees C, 45% water-holding capacity) was established using 14C-labelled glucose and rice straw (500 mu g 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 themineralization of native organic C in the paddy soil, while the priming effect was significant in the upland soil. CONCLUSION: Although thepaddysoil containsalargeamountof microbial biomass, whichis also veryactive, themineralization 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. (C) 2011 Society of Chemical Industry