Annual and Perennial Peanut Species as Alternatives to Nitrogen Fertilizer in Bermudagrass Hay Production Systems

Abstract

Core Ideas Grass–legume forage systems outperformed grass monocultures. Arachis glabrata had greater potential for N2 fixation than other peanut species. Grass enhanced its nutritive value and obtained N from legumes when grown in mixtures. Bermudagrass hybrids (Cynodon spp.), such as Tifton 85, are among the most widely used forages for hay production in the southeastern United States, although large N fertilizer inputs are often required for sustained productivity. Grass–legume mixtures can reduce the need for N fertilization. The objective was to assess peanut species (Arachis spp.) as alternatives to N fertilizer. One annual species (Arachis hypogaea L. cv. TUFRunner ‘727’) and two perennials, pintoi peanut (A. pintoi Krap & W.C. Greg cv. ‘Amarillo’) and rhizoma peanut (RP; A. glabrata Benth., cv. ‘Florigraze’ and germplasm Ecoturf) were evaluated in Tifton 85 swards. Planting occurred in 2014 and mixtures were evaluated through 2016. Responses included herbage accumulation (HA), peanut proportion in HA, nutritive value, biological nitrogen fixation (BNF), %N derived from atmosphere (%Ndfa), and %N of grass N that was transferred from peanut. Ecoturf–grass mixtures had the greatest HA (900 kg DM ha−1 harvest−1), while TUFRunner 727–grass mixtures had the least (690 kg DM ha−1 harvest−1). Mixing peanuts with Tifton 85 increased in vitro digestible organic matter (IVDOM) concentration of the grass from 588 g kg−1 in monocultures to 620 g kg−1 in mixtures, but did not increase grass crude protein (CP) concentration. Contribution of Amarillo peanut was minimal throughout the study, TUFRunner 727 contributed significantly in the year of planting only, but RP contribution increased each year. Although peanut species were unable to replace the amount of N typically applied to bermudagrass hay fields, there is evidence RP in particular could contribute to mixture productivity and nutritive value.