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ARS Home » Plains Area » Lubbock, Texas » Cropping Systems Research Laboratory » Wind Erosion and Water Conservation Research » Research » Publications at this Location » Publication #405239

Research Project: Developing Strategies for Resilient and Sustainable Crop, Water, and Soil Management in Semi-Arid Environments

Location: Wind Erosion and Water Conservation Research

Title: Mechanisms of cover crop-mediated soil carbon storage in a semi-arid irrigated cropping system

item ACHARYA, PRAMOD - New Mexico State University
item GHIMIRE, RAJAN - New Mexico State University
item Acosta-Martinez, Veronica

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2023
Publication Date: 11/19/2023
Citation: Acharya, P., Ghimire, R., Acosta Martinez, V. 2023. Mechanisms of cover crop-mediated soil carbon storage in a semi-arid irrigated cropping system. Geoderma. 361.

Interpretive Summary: Soil organic matter (SOM) is a central focus in evaluating soil health due to its impact on all the other soil properties (e.g., physical, chemical, and biological). Using cover crops during the winter has shown to increase SOM and ultimately improve soil health in regions where water is not a limited factor for crop production. It is not known if cover crops could also be helpful to increase soil health in arid and semi-arid regions of USA due to limited precipitation. Thus, scientists from New Mexico State University and USDA-ARS in Lubbock, TX, tested different cover crops (brassica, grasses, legumes, and their mixtures) for a silage corn-sorghum rotation during the first four years of establishment in Clovis, NM. The scientists found improvements in SOM and other soil physical, chemical, and biological indicators of soil health within the third year compared to the system without a winter cover crop. For example, many SOM pools and the soil microbial component were greater under the system with cover crops, but the effects were not consistent in all years of the study. The scientists identified two major drivers of carbon sequestration in semi-arid forage production systems: 1) Microbial-mediated carbon sequestration mostly related with relatively stable pools, i.e., Mineral Associated organic carbon (MAOC), and 2) Physicochemical properties, mainly soil pH and mineral N availability, affected particulate organic carbon (POC), which is a labile SOM pool and that was sensitive to management. Additionally, the scientists suggest the inconsistencies in the response of soil indicators during the study reveals the need to conduct long-term studies that can include an evaluation of the extreme yearly climatic variability typical in semi-arid and arid regions.

Technical Abstract: Cover cropping is a climate-smart strategy to regenerate low-fertility soils in arid and semi-arid regions because of the multiple benefits of cover crops. However, the mechanisms of soil organic carbon (SOC) storage and soil health improvement in semi-arid irrigated cropping systems are poorly understood. The main goal of this study was to evaluate cover crop effects on various soil health indicators representing physical, chemical, and biological health in an irrigated forage corn (Zea mays L.)–sorghum [Sorghum bicolor (L.) Moench] rotation and understanding how microbial community and other properties contribute to SOC storage. We compared cover crop mixture of grasses, brassicas, and legumes (GBL), grasses and brassicas (GB), grasses and legumes (GL), and no cover crops (NCC) control for four years. Grasses included annual ryegrass (Lolium multiflorum) and winter triticale (Triticale hexaploid Lart.), brassicas included turnip (Brassica rapa subsp. rapa) and daikon radish (Raphanus sativus var. Longipinnatus), and legumes included pea (Pisum sativum subsp. arvense L.) and berseem clover (Trifolium alexandrinum L.). Soil C pools: SOC, SOC mineralization, microbial biomass C, mineral-associate organic C (MAOC), and particulate organic C (POC) were greater under cover crops than under NCC, but the effects were not consistent in all study years. Soil organic N also mostly increased under cover crops. Soil C-to-N ratio also increased over years but was similar among treatments. Cover crops utilized N and soil water for their growth, significantly reducing soil inorganic N content in the first two years. Fungal and bacterial community sizes were generally greater under cover crops with an increase in fungi-to-bacteria ratio compared to NCC. Integrating cover crops in semi-arid cropping systems, specifically in forage cropping, could improve soil physical, chemical, and biological properties, overall soil health, and SOC storage.