Development of Best Management Practices for Enhancing Soil Health in Semi-Arid Transitional Organic Cropping Systems

The Southern Great Plains (SGP) are marked by challenging climate conditions, such as low annual precipitation (381 to 711 mm) and high wind velocities. The adoption of organic management practices, such as crop rotation, cover cropping, and organic fertilizer usage, can enhance water conservation, build organic matter, and lower the risk of erosion. However, tangible improvements in soil health parameters are crucial to persuade producers to consider organic transition. The objective of this study was to determine the agronomic viability and effects of traditional and non-traditional organic cover crops and crop rotation on soil health parameters, stored soil moisture, and CO2 emissions. Field studies were established in the Texas High Plains (THP) at Lamesa, Texas, and in the Texas Rolling Plains (TRP) at Vernon, Texas, from 2021-2023. The cropping systems at each site were continuous cotton (Gossypium hirsutum L.) (CC), cotton/peanut (CP) (Arachis hypogaea L.) at Lamesa and cotton/mungbean (Vigna radiata L.) (CM) at Vernon, cotton/sesame (Sesamum indicum L.) (CS), and cotton/wheat/forage sorghum sudangrass (Sorghum bicolor x Sorghum sudanense) (CWH). The cover crop treatments were rye at 17 kg ha-1 (Rye17), rye at 34 kg ha-1 (Rye34), fennel/fenugreek (FF) mix at 8.5/8.5 kg ha-1, rye/fennel/fenugreek (RFF) at 25/6/6 kg ha-1. Soils at both sites were characterized for key physical, chemical, and biological soil health parameters, and crop yields and cover crop herbage mass were determined annually. Additionally, at Lamesa, stored soil moisture and CO2 emissions were measured in 2022, and weed cover in 2023. Crop yields and cover crop herbage mass were generally low because of drought and weed pressure. Still, the cropping system most influenced changes in soil health parameters at both sites. Mean weight diameter (MWD), total microbial biomass, and certain microbial communities (AMF, G+ bacteria) were most improved during the transition period to organic production. Soil organic carbon (SOC) stocks increased from 14 to 43% at Vernon and from 22 to 31% at Lamesa between 2021 and 2023, although differences between cropping systems were minimal. At Lamesa, sorghum sudangrass produced the greatest herbage mass in 2022, which lowered weed pressure, enhanced stored soil moisture, and increased SOC. While high herbage mass resulted in high CO2 flux in 2022, approximately 50% of the C lost was replaced by crop residues. Increases in microbial abundance (fungi, AMF, and G+) allude to positive trends in C sequestration, especially when crop rotation is practiced. Our results highlight that changes in soil health parameters because of organic transition are influenced by ecoregion, land history, and management decisions (plant selection, compost application frequency, planting, and termination timing). We recommend further research to develop regionally appropriate best-management practices for semiarid transitional organic cropping systems to address weed pressure, conserve soil water, and build SOC.