Growth Analysis of ‘Florigraze’ Rhizoma Peanut: Forage Nutritive Value

Abstract

Abstract‘Florigraze’ rhizoma peanut (Arachis glabrata Benth.) is a perennial tropical forage legume grown in Florida and the southern Gulf Coast. Two field studies were conducted near Gainesville, FL on Arredondo loamy sands (loamy, siliceous, hyperthermic, Grossaremic Paleudults) in 1980 and 1981. The objective of these studies was to evaluate nutritive value of Florigraze topgrowth as measured by crude protein (CP) and in vitro digestible organic matter (IVDOM). Experiment 1 was an establishment‐year growth analysis study conducted at two sites (years). Experiment 2 was a defoliation‐frequency study (0 vs. 2, 6, and 8 wk) conducted in 1981 on plants that were undisturbed at the 1980 site. Samples were taken periodically during the growing season in both years. In Exp. 1, both CP and IVDOM concentrations were characterized by two‐stage curves, where CP and IVDOM declined linearly (−0.9 and −0.7 g kg−1 d−1) until September, then stabilized at 125 and 610 g kg−1, respectively. Leaves constituted 60 to 80% of top growth in both years. In Exp. 2, CP and IVDOM declined linearly (−0.3 and −1.0 g kg−1 d−1) during the growing season for all defoliation treatments. Decline in percent leaf in the established plants of Exp. 2 was twice that of undisturbed plants in Exp. 1: −0.10 vs. −0.05 percentage units d−1. There was a sampling date × defoliation treatment interaction (P < 0.001) in percent leaf. Values for undefoliated plants were similar to that of Exp. 1, but leaf percentages declined at increasing rates in all defoliation treatments. At four dates in Exp. 1 and three dates in Exp. 2, top growth was separated into leaves and stems for IVDOM analysis. Leaf IVDOM declined linearly (−0.3 g kg−1 d−1), while stem IVDOM declined and then increased slightly from September through December. The data suggested that leafiness can be altered by defoliation management, and in turn, leafiness influences forage nutritive value of Florigraze rhizoma peanut.