Multi-species cover cropping promotes soil health in no-tillage cropping systems of North Carolina

Authors: Franzluebbers, Alan; BROOME, STEPHEN - North Carolina State University; PRITCHETT, KATHERINE - North Carolina State University; WAGGER, MICHAEL - North Carolina State University; LOWDER, NATHAN - Natural Resources Conservation Service (NRCS, USDA); WOODRUFF, STEVE - Natural Resources Conservation Service (NRCS, USDA); LOVEJOY, MICHELLE - North Carolina Foundation For Soil And Water Conservation

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2020
Publication Date: 5/7/2021
Citation: Franzluebbers, A.J., Broome, S.W., Pritchett, K.L., Wagger, M.G., Lowder, N., Woodruff, S., Lovejoy, M. 2021. Multi-species cover cropping promotes soil health in no-tillage cropping systems of North Carolina. Journal of Soil and Water Conservation. 76:263-275.

Interpretive Summary: Multi-species cover cropping (i.e. growing several different species of cover crops in the same field at the same time) has been promoted as a top-tier conservation approach for growers that want to improve soil health. However, limited data are available in North Carolina to show how effective the practice might be in establishment, biomass accumulation, and its effects on soil properties. A scientist with the USDA-Agricultural Research Service in Raleigh NC collaborated with investigators from North Carolina State University, USDA-Natural Resources Conservation Service, and North Carolina Foundation for Soil and Water Conservation to assess changes in soil properties from a series of 31 trials conducted on farmer’s fields throughout North Carolina. Biomass production was good to excellent in about two-thirds of the trials. Greater nitrogen accumulation in cover crop biomass was possible with multi-species cover crops than typical cereal grains due to significant legume proportion of the mix. Soil biological properties were improved in side-by-side strips of multi-species cover crops compared with no cover crops or single-species cover crops, implying that subsequent cash crops would have greater fertility conditions through supply of bio-available nitrogen and improvement in soil physical properties. Soil-test phosphorus and potassium, on the other hand, were often reduced under multi-species cover cropping than without cover crops, suggesting that release of these elements from cover crop residues would be needed. This study demonstrated that the majority of growers can successfully grow multi-species cover crops with high biomass production, and that these cover crops can improve soil conditions to create a more resilient agricultural system.

Technical Abstract: Moving agricultural production systems towards a greater level of soil health is needed for a sustainable future. Conservation agricultural systems utilizing no or minimum tillage is an important step forward, but enhancing C inputs and facilitating biologically active nutrient cycling is also needed. Summer cash-crop systems, particularly in the warm-humid region of the southeastern US, may benefit from multi-species winter cover cropping if sufficient biomass were produced. We implemented a research and demonstration project utilizing multi-species cover cropping in 15 counties of North Carolina during 2015-2019 to assess biomass production and its effect on surface-soil properties. Winter cover-crop biomass production was variable among locations, but production exceeded 3790 kg ha-1 (3384 lb/acre) in one-third of trials. Nitrogen contained in cover crop biomass exceeded 60 kg ha-1 (54 lb N/acre) in the upper third of trials. From 27 soil properties measured at each site-year (n = 31) at depths of 0-5 and 5-15 cm, soil-test biological activity, C mineralization during 24 days, total soil N, and Mehlich-III P and K were the most consistently affected properties in comparison of multi-species cover cropping with either no cover crop or single-species cover cropping. Despite relatively short duration of evaluations (i.e. mostly 1-2 years), we were able to elucidate that winter multi-species cover cropping has potential to improve soil health conditions in the region. Farmers interested in adopting this conservation approach to sustainable agriculture have evidence to support their decisions, but also the support of a hands-on farmer network developed around this approach.