NITROGEN LIMITATION OF RHIZOMA PEANUT GROWTH

Rhizoma peanut (Arachis glabrata) is a forage and groundcover crop of increasing importance in the southeastern United States, but little is known of its nitrogen (N) requirement for optimal production, or if this requirement is being met through symbiotic nitrogen fixation. Nitrogen fertilization greenhouse experiments were performed with Florigraze and Ecoturf genotypes and response measured by shoot production, nodulation, nitrogenase activity, shoot N concentrations, and N accumulation. Rhizome N concentrations with and without N fertilization were also evaluated in the field. From the two greenhouse studies, we found a saturating response to N fertilization between 11 and 23 kg N ha-1 during the 11-week evaluation period. In both the greenhouse, and to a lesser extent, the field experiment, N accumulation was found to increase with increased N fertilization, which indicates that N2-fixation may not provide the necessary N for optimal shoot production.