Soil Microbial Communities in Claypan Soils.

Claypan soils are characterized by a dense, impermeable subsoil that impedes root system development, in part because of the physical restriction of root growth. Changes in nutrient, water, and oxygen availability in the clay layer may further restrict root growth. The functional diversity of soil microbial communities can potentially indicate the microenvironment that supports root growth, and hence the productive capacity of the soil. The soil microbiology has not been studied in detail in claypan soils. Soil microbial community were examined through PLFA, and two enzyme groups, hydrolases and oxidases, are considered in this study. Hydrolytic enzymes (hydrolase) decompose complex organic compounds, and oxidative enzymes (oxidase) destabilize phenolic compounds from organic matter in the soil. Ratios of enzymatic activities are correlated with the relative abundance of labile/recalcitrant carbon (C) or relative nutrient availability. Thus, the activity ratios can also be used as indicators of microbial nutrient demand and soil nutrient status. The results were stratified where soil properties in the top 15cm were affected by agricultural management and soil properties below 35cm were determined by inherent soil profile characteristics. The soil layer between 15 to 35 cm appeared to have a mix of inherent properties and surface management. Clay content, soil moisture and C were key drivers of microbial properties. High clay content was usually coincident with high soil organic carbon (SOC) and high hydrolase activity. Tillage reduce microbial activity.