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

Abstract

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.