Biological N2-Fixation, Belowground Biomass, and Forage Potential of Rhizoma Peanut (Arachis glabrata Benth) Varieties.

Rhizoma peanut (Arachis glabrata Benth) is a warm-season perennial legume adapted to Southeast USA. Rhizoma peanut (RP) is mostly used as a hay crop in North Florida, but it can also be managed under grazing. Although RP has been extensively used, there are limited data on Biological N₂-fixation (BNF) for this species, particularly for the recent released varieties.  Seven RP varieties were evaluated in this harvest trial performed in 2014. Varieties used included Arblick, Arbrook, Ecoturf, Florigraze, Latitude 34, UF Peace, and UF Tito. Treatments were allocated in a randomized block design, with four replications per treatment. Harvests occurred in 6 June, 13 August, and 14 October 2014. Measured response variables included dry matter yield, N concentration, N yield, %N derived from atmosphere (%Ndfa), BNF, IVOMD, and root + rhizome mass. Dry matter yield ranged from 6.0 (Florigraze) to 10.3 (Arbrook) Mg ha^-1 yr^-1, with an average yield of 8.0 Mg ha^-1 yr^-1. Root and rhizome biomass represented significant proportion of the standing biomass, ranging from 10.8 (Florigraze) to 23.0 (Ecoturf) Mg DM ha^-1. Digestibility (IVOMD) averaged 730 g kg^-1 and did not differ among cultivars, except for Arbrook that presented a lower value (676 g kg^-1). Herbage N concentration varied with harvest, ranging from 23 to 38 g kg^-1. Nitrogen yield ranged from 136 to 237 kg N ha^-1 yr^-1 for Florigraze and UF Peace, respectively. The %Ndfa was high for all cultivars, ranging from 70 to 94%, resulting in a BNF ranging from 110 to 196 kg N ha^-1 yr^-1, for Florigraze and UF Peace. Results indicated the potential of RP to add N and increase forage nutritive value in livestock production systems.