Expanding Soil Health Assessment Methods for Agricultural Systems of the Southern Great Plains.

In agricultural systems, soil health (also referred as soil quality) is critical for sustainable production and ecosystem services. Soil health analyses dependent upon singular parameters fail to account for the host of interactions occurring within the soil ecosystem.  Soil health is in flux with microbial communities and environmental factors, and as such is a difficult parameter to comprehensively define and measure.  Soil health is generally defined as the capacity of a soil to function within ecosystem and land use boundaries, to sustain productivity while maintaining environmental quality, and to promote plant and animal health.  Healthy soils generally have high microbial diversity, which is linked to higher productivity.  Plant nutrition and greenhouse gas (GHG) emissions are linked to soil microbial diversity and function, as varying soil microbes produce GHGs in different amounts.  Therefore, soil microbial diversity measurements are contemplated as indices to assess soil health function; however, there is no consensus on how to accurately combine each of these individual parameters.  With this study, we propose to expand the soil health assessment by including multiple microbial diversity estimates, and identify dynamic, yet complementary correlations with PLFA based microbial biomass and diversity estimates and soil nutrient pools. We conducted this study on natural tall grass prairie under burn intervals and forage sorghum rotations under tillage and grazing management to evaluate the soil health in relation to soil carbon sequestration, microbial biomass and diversity.   We used a combination of enhanced gravimetric methods and water extractable organic carbon analysis to determine the carbon sequestration potential. Strong bivariate correlations were observed between microbial biomass, C and N pools and microbial diversity in surface soils; however, the correlations were weak in subsurface soil layers.