TOTAL NONSTRUCTURAL CARBOHYDRATES AND NITROGEN OF FLORIGRAZE RHIZOMA PEANUT

'Florigraze' rhizoma peanut (Arachis glabrata Benth.) is a perennial, rhizomatous forage legume that is grown in Florida and the southern Gulf Coast. Little is known about total nonstructural carbohydrate (TNC) or N concentrations in plant parts of rhizoma peanut. Two field studies were conducted near Gainsville, FL on Arredondo loamy sands (loamy, siliceous, hyperthermic Grossarenic Paleudults) to determine (i) which plant component(s) serves as primary TNC and N storage organ(s), (ii) pattern of TNC and N accumulation in undisturbed plants, and (iii) effects of defoliation upon TNC and N. An establishment-year study was conducted in 1980 and 1981 using spaced plants, and a defoliation-frequency study (undefoliated vs. defoliated every 2, 6, or 8 wk) was conducted in 1981 on plants that were undisturbed in 1980. Entire plants (hills) were dug every 3 to 8 wk throughout the year and separated into shoots and primary and secondary rhizomes. Shoot TNC concentration showed no pattern of accumulation. Concentrations of TNC and N were similar in primary and secondary rhizomes. In new plantings, rhizome TNC declined in early-season to 100 g kg-1, was low and variable (100-200 g kg-1) from May through September, and increased to 400 g kg-1 by November. Rhizome N declined from 30 g kg-1 in spring to 20 g kg-1 during the establishment year with a slight increase in autumn. All defoliation treatments reduced TNC and N concentrations of rhizomes compared to nondefoliated peanuts. Florigraze accumulates a high concentration of TNC (400-700 g kg-1) in its rhizomes in autumn. Our data suggest that defoliation should be avoided for establishing plants and plants that will be used as a source of rhizomes for propagation.