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ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Publications at this Location » Publication #395978
Research Project: Combined Management Tactics for Resilient and Sustainable Crop Production

Location: Integrated Cropping Systems Research

Title: Grazing management modifies the biomass and activities of soil microorganisms in grasslands

Author
item Lehman, R - Michael
item WHITE, LAURA - Former ARS Employee

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2022
Publication Date: 6/11/2022
Citation: Lehman, R.M., White, L.J. 2022. Grazing management modifies the biomass and activities of soil microorganisms in grasslands. Soil and Water Conservation Society Annual Meeting, Denver, CO, July 31-Aug 3, 2022.

Interpretive Summary:

Technical Abstract: Variable reports regarding the effects of grazing management on soil properties in grasslands suggest the need for further study. We measured the response of soil microbiological properties to conventional and adaptive multi-paddock (AMP) grazing management practices at five locations arranged in a north-south transect from southern Kentucky to Southern Mississippi. At each location, sampling transects were established at neighboring ranches with contrasting management practices, and 18 independent, composite soil samples were collected and preserved according to analysis. We measured abundance of taxonomic groups by quantitative PCR (qPCR), potential nutrient cycling activities by qPCR of functional genes, and potential mineralization activities including basal respiration and substrate-induced respiration (SIR) with glucose and phenol as substrates. Numbers of fungi (p=0.060) and bacteria (p=0.119) were higher under AMP management compared to conventional management. The numbers of gene copies encoding for nitrification and denitrification were higher (p=0.032 and p=0.027, respectively) in AMP ranches compared to the Conventional ranches. Basal soil respiration was elevated (p=0.125) in AMP ranches compared to Conventional ranches presumably due to the higher numbers of microbes that were actively transforming plant exudates and residues. In contrast, carbon limitation of respiratory activities was higher (p= 0.011) in the Conventional ranches compared to AMP ranches indicating decreased processing of soil C and formation of microbial biomass which are the key processes leading to stable soil carbon. In summary, we found grazing management can influence the numbers and key activities of soil microbes that may increase retention of C and nutrients in these grassland systems.