|THAPA, VESH - New Mexico State University|
|GHIMIRE, RAJAN - New Mexico State University|
|MARSLIS, MARK - New Mexico State University|
|SCHIPANSKI, MEAGAN - Colorado State University|
Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2020
Publication Date: 8/31/2020
Citation: Thapa, V.R., Ghimire, R., Acosta Martinez, V., Marslis, M.A., Schipanski, M. 2020. Cover crop biomass and species affect soil microbial community structure and enzymatic activities in semiarid cropping systems. Applied Soil Ecology. 157(2021):103735. https://doi.org/10.1016/j.apsoil.2020.103735.
Interpretive Summary: The use of cover crops has been suggested as means to improve soil health in agricultural systems. One way to track changes in soil health after adopting new management practices is by analyzing soil microbes and their activities. Scientists from New Mexico State, USDA-ARS in Lubbock TX, and Colorado State University evaluated different cover crops (barley, canola, forage radish, oat, pea, and different mixtures of them) in a semiarid soil with limited irrigation during 2017 and 2018. Planting oat as a cover crop, significantly increased fungal populations when compared to fallow. This is important because fungi are beneficial microbes that can increase soil aggregation and nutrient availability for plant growth. Moreover, most cover crops increased enzyme activities associated to carbon and nitrogen availability for plant growth. Overall, results from this study demonstrate that cover cropping has the potential for improving soil health in a hot semiarid zone near New Mexico.
Technical Abstract: Cover crops are promoted to improve soil organic matter storage and soil biological health in agricultural systems, yet their role on soil microbial community structure and functioning are not clear in semiarid environments. This study investigated soil microbial community structure and enzyme activities under limited-irrigation winter wheat (Triticum aestivum)- sorghum (Sorghum bicolor)-fallow with cover crop integration. The study had a randomized complete block design with eight treatments and three replications. Treatments were pea (Pisum sativum), oat (Avena sativa), canola (Brassica napus L.), and mixtures of pea + oat (POmix), pea + canola (PCmix), pea + oat + canola (POCmix), pea + oat + canola + hairy vetch (Vicia villosa) + forage radish (Raphanus sativus L.) + barley (Hordeum vulgare L.) (diverse-mix) as cover crops and a fallow. Cover crops were grown from February through May before planting wheat and sorghum, and soil samples were collected in the summer of 2017 and 2018 from 0-15 cm depth of each plot and analyzed for soil microbial community size and structure by Ester-linked fatty acid analysis, and microbial functions by enzyme analysis. Community size for soil fungi was 47.8 nmol g-1 soil under oat, which was similar to diverse-mix and 41% greater than fallow. The community size of arbuscular mycorrhizal fungi was 84% greater under oat than fallow. The combined enzyme activity (acid phosphatase, ß-glucosidase, and ß-glucosaminidase) was 294 mg PNP kg-1 soil h-1 under diverse-mix, which was significantly greater than fallow (204 mg PNP kg-1 soil h-1) in 2018. Cover cropping during the fallow period increased fungal abundance and combined enzyme activities associated with C and N cycling. Oat and its mixture with legumes (pea and hairy vetch) and brassicas (canola and forage radish) have the potential to improve soil biological health in a hot and dry semiarid climate.