Mineral-associated organic C (MAOC) is derived primarily from the microbial necromass (products of microbial metabolism) complexed with minerals, which constitutes 71.5% of soil organic C in croplands and plays a crucial role in long-term soil C storage and stabilization. Understanding the microbial mechanisms of MAOC accumulation is crucial to promoting C sequestration in cropland.
In the most recent study published in Soil Biology and Biochemistry on May 27th, researchers led by Prof. Wu Jinshui from the Institute of Subtropical Agriculture, Chinese Academy of Science , collected subtropical paddy soil samples along the organic C gradient ranging from 4.0 to 40.1 g kg^-1 to investigate the relationship between MAOC accrual and microbial metabolism using a combination of size fractionation, ¹⁸O-H₂O incubation, and biomarker techniques analyses.
As soil organic C increased whilst MAOC tended to saturation. Notably, MAOC accumulation showed a significant positive relationship with microbial necromass indicating that MAOC accumulation prior to saturation was closely linked to the activity of microbial C metabolism. Compared to high-fertility paddy soils, the low-fertility counterparts exhibit stronger microbial anabolism, faster biomass turnover rate, and greater necromass accumulation coefficients.
“This study advances our understanding of the complex microbial constraints underlying MAOC accumulation, and provides experimental evidence that MAOC accumulation is directly influenced by microbial metabolic activity in subtropical paddy soils.” said Prof. Guo Xiaobin, the corresponding author of the study, “For the low-fertility paddy soils, strategies designed to support microbial anabolism and accelerating biomass turnover rates should be investigated as a means of enhancing MAOC accumulation.”

Diagram illustrating microbial C metabolism and necromass formation affect mineral-associated organic C accumulation in subtropical paddy soils (Image by Zhe Li)

Contact: Guo. Xiaobin
E-mail: gxbguo@gmail.com