Yield and Reserve Status of Rhizoma Peanut Growing under Shade

Abstract

‘Florigraze’ rhlzoma peanut (Arachis glabrata Benth.) is a perennial legume of high forage quality, but commercial use has been limited by slow establishment. In the southeast USA, the understory of pine (Pinus spp.) plantations is grazed by cattle (Bos spp.). Because grazing must be deferred during pine establishment, concurrent planting of trees and Horigraze might facilitate use of the legume and improve the quality of forage for grazing. To determine if trials evaluating Florigraze‐pine associations are warranted, preliminary information on Horigraze shade tolerance is needed. A 3‐yr field study was conducted on a Kendrick soil 0uamy, siliceous, hyperthermic Arenic Paleudult) to determine Horigraze growth and reserve status in response to shading and defoliation intensity. Main plots were shade treatments that were defined as percentages of incident photosynthetic photon flux density (PPFD; 34, 54, 78, and 100%); subplots were defoliation stubble heights (4 or 8 cm). Treatments were replicated three times, and plots were harvested four times in 1989, three times in 1990, and once in early summer 1991. Summed across harvests within years, dry matter (DM) yield increased as PPFD increased from 34 to 100% (5.6‐8.8 Mg ha‐1 in 1989 and 3.3‐11.3 Mg ha−1 in 1990). Rate of increase in DM yield was slower as PPFD increased, and yield generally was greater for the 4‐ than 8‐cm clipping height. For 78 and 54% PPFD, annual Florigraze yields were >90 and 70% as great as those for the 100% PPFD treatment in 1989 and 1990. At season end 1989 and 1990, rhizome mass and total nonstructural carbohydrate (TNC) concentration decreased with decreasing PPFD, but values for shaded treatments in 1990 were at least as great as those in 1989. We conclude that rhizoma peanut‐pine associations merit evaluation because Horigraze was productive and persisted well at PPFD levels similar to those observed in pine understories.