Relationship of crop yield to microbial biomass in highly-weathered soils of China

Abstract

In highly weathered soils, plant nutrients derived from mineral weathering are very limited. Laboratory analysis and greenhouse experiments were carried out to examine the relationship of crop yield to soil microbial biomass with eight highly weathered soils of varying fertility levels. Microbial biomass carbon (Cmic) ranged from 20.2 to 425.8 mg kg-1, accounting for, on average, 1.88% of total organic carbon (Corg). The Cmic was closely related to Corg, total N, and available N in the soils. Microbial biomass nitrogen (Nmic) ranged from 4.02 to 52.6 mg kg-1, accounting for, on average, 2.88% of NT or 28.8% of NA. The Nmic was closely related to Corg, Cmic, NT, and NA. Plant N uptake (Nuptake) was significantly correlated with Corg, NA, Cmic, Nmic, and NT. Ryegrass dry matter yield was better correlated with Cmic or Nmic than with Corg, NA or NT. These results indicate that soil microbial biomass is one of the most important fertility sustainability indices of highly weathered soils.