COS 28-2 - Identifying soil health indicators linked to essential functions for water limited regions

Abstract: Maintaining soil health, biodiversity, and sustaining crop production for semi-arid regions will be challenging due to increasing weather variability from climate change, and an accelerated transition from irrigated to dryland management. Many indicators of soil health are correlated with soil organic matter (SOM), but semi-arid regions like the Southern High Plains (SHP) have, low soil organic matter (SOM) content (typically < 1%) and precipitation (< 450 mm), which limits biomass production and options for sustainable land management. Cotton producers transitioning to dryland management have adopted several alternative management practices including conservation tillage and cover cropping to improve soil water conservation, however, it may take many years to detect changes in soil water holding capacity caused by conservation management practices in arid regions. We evaluated biological indicators of soil health such as different characteristics of the soil microbial community and labile pools of SOM that may better represent improvement in soil health for soils in water-limited regions with low SOM. Among the measurements were ester linked-fatty acid methyl ester EL-FAME analysis, enzyme activities of nutrient cycling, and pools of SOM like microbial biomass C, POXC, and SOC. Over four years (2019-2022), we sampled 19 cotton fields in the SHP that are in early stages of transitioning to conservation management with reduced tillage and winter-wheat cover cropping. The fields were referenced against fields under conventional tillage cotton and fields converted to grassland. Significant improvements in these soil health indicators were detected two years into transition for fields under no-till center pivot or no-till dryland management. Our study will also add evaluation of soil water infiltration to offer a framework for soil health assessment for these management strategies in a water-limited environment that links different soil health indicators with soil functions related to soil water, biogeochemical cycling, soil organic matter and productivity.