Soil health assessment to evaluate conservation practices in semi-arid cotton systems at producer sites scale

Authors: Acosta-Martinez, Veronica; Cotton, Jon; SLAUGHTER, LINDSEY - Texas Tech University; GHIMIRE, RAJAN - New Mexico State University; Roper Iii, Wayne

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2023
Publication Date: 8/9/2023
Citation: Acosta Martinez, V., Cotton, J.E., Slaughter, L., Ghimire, R., Roper III, W.R. 2023. Soil health assessment to evaluate conservation practices in semi-arid cotton systems at producer sites scale. Agronomy Journal. 7(3). https://doi.org/10.3390/soilsystems7030072.
DOI: https://doi.org/10.3390/soilsystems7030072

Interpretive Summary: Conservation tillage and cover crops are used less frequently in the Southern High Plains compared to other regions of the USA. However, these practices can particularly benefit soils in this region, which have low soil organic matter content (typically <1%) due to the low plant biomass produced in response to low and inconsistent precipitation. Scientists from USDA-ARS in Lubbock TX, Texas Tech University, and New Mexico State University conducted a soil health assessment in several producer fields transitioning to no-tillage and winter wheat as a cover crop for cotton production, and evaluated land under the Conservation Reserve Program and farms that remained under conventionally tilled continuous cotton. Significant improvements in several soil health indicators were detected in farms under no-tillage center pivot and even under dryland for two years, and sites that were initiated under these practices also showed improvements in soil health by year 2 when compared to conventionally tilled cotton. These results suggest improvements in soil health with conservation practices are possible under the challenge of water scarcity and environmental stress in semiarid regions. The Conservation Reserve Program always had significantly higher levels of measured soil health indicators, once again demonstrating the benefits of this program for soil health restoration efforts of fragile soils of this region. More research is needed to understand the long-term trends in the Southern High Plains for these conservative practices.

Technical Abstract: Maintaining soil health, biodiversity, and sustaining crop production for semiarid regions will be challenging due to increasing weather variability from climate change, and an accelerated transition from irrigated to dryland management in many regions. An example of this challenge occurs in the Southern High Plains (SHP), a major cotton-producing region where soil organic matter (SOM) is typically less than 1% and 450mm of annual precipitation limits biomass production and many management options. One possibility available to producers is transitioning to reduced or no-tillage practices for cotton production with the use of a winter cover crop such as rye or wheat. To understand the initial transition of cotton cropping to no-till with wheat as a cover crop, we sampled 19 commercial grower sites across this region encompassing 13,000 acres under different water levels (subsurface irrigation, center pivot and dryland) from 2019-2022. Most of the sites transitioned to no-till in 2017, two years before sampling began, with two sites transitioning the year after initial sampling. We also sampled reference sites which represented farms under conventional tillage cotton and grasslands under the Conservation Reserve Program (since 1986). Adaptation of winter cover crops has traditionally met resistance in water-limited regions due to concerns of reducing soil water available to summer cash crops. However, improvements in soil health have the potential to offset some of this loss with increases in infiltration and soil water holding capacity. To better understand the early changes in soil health and provide land managers feedback on a more reasonable time-frame, we evaluated the soil microbial community size and composition via ester linked-fatty acid methyl ester (EL-FAME), enzyme activities involved in nutrient cycling, and measurements of several pools of SOM such as microbial biomass C and N, permanganate-oxidizable C (POXC), and total soil C and N via combustion. Significant improvements in these soil health indicators were detected in farms under no-tillage center pivot and even under dryland for two years, and by year 2 of the transition of the most recent system sampled after the first year of the transition when compared to conventionally tilled cotton. Continuation of these studies will provide long-term trends under different climatic conditions at producer level fields and will offer a framework for soil health assessment for these management strategies in a water-limited environment. Long-term studies will also be able to establish linkages between different soil health indicators and soil functions related to soil water, biogeochemical cycling, soil organic matter and productivity.