INFLUENCE OF SOIL PROPERTIES ON MICROBIAL C, N, AND P IN DRY TROPICAL ECOSYSTEMS

Relationships between soil physicochemical characteristics and soil microbial C, N, and P in Indian dry tropical ecosystems are discussed. The major ecosystem studies were on forest, savanna, cropped fields, and mine spoils. The highest microbial C, N, and P levels were recorded from the mixed forest and the lowest levels in 5-year-old mine spoil. Across the sites, microbial C ranged from 226 to 643-mu-g g-1, microbial N from 19 to 71-mu-g g-1, and microbial P from 9 to 28-mu-g g-1 soil. The proportion of soil organic C contained in the microbial biomass ranged from 2.2 to 5.0%. The microbial C : N ratio in these soils ranged from 7.4 to 13.1 and the microbial C : P ratio from 16.6 to 30.6. The concentrations of microbial C, N, and P were correlated with several soil properties and among themselves. The soil properties, in various linear combinations, explained 90-99% of the variability in the microbial nutrients. Grazing of the savanna had some effect on the level of microbial biomass, and as the mine spoil aged, the level of microbial C, N, and P also increased.