Microbial biomass in red soils and its significance in plant availability of nitrogen

A series of laboratory and pot experiments carried out to examine the role of soil microbial biomass in red soils’ nitrogen availability and productivity showed that soil available N (N\-A), dry matter yield (DMY) of ryegrass, and plant uptake of nitrogen were each closely correlated with microbial biomass\|C (C\-\{mic\}) or \|N (N\-\{mic\}), suggesting that soil microbial biomass is a very important nitrogen pool available to plants in red soils. After correction for the substrate effect, the computed turnover of the N\-\{mic\} in three tested soils ranged from 63 to 250 days. Soils with low N\-\{mic\} or light texture generally had higher N\-\{mic\} turnover rate than those with high N\-\{mic\} or heavy texture. These results showed that soils with low N\-\{mic\}, microbial biomass could also play an important role in the availability of nitrogen to plants due to these soils’ high turnover rate.