Herbage responses of signalgrass under full sun or shade in a silvopasture system using tree legumes

Abstract

AbstractSilvopasture systems enhance the use efficiency of natural resources by diversifying vegetation structure and function. However, shading from trees may affect the production and quality of herbaceous forages and, consequently, the animal performance. The objective of this research was to evaluate regrowth and development of tree legumes as well as productivity and nutritive value of signalgrass [Brachiaria decumbens (Stapf) R.D. Webster] subjected to shading from the tree legumes gliricidia [Gliricidia sepium (Jacq.) Steud] and sabiá (Mimosa caesalpiniifolia Benth.). Herbage responses were evaluated every 56 d. Trees were evaluated every 120 d to assess morphological responses and forage nutritive value. Response variables included in vitro digestible organic matter (IVDOM), concentrations of N, and stable isotopes (δ15N) in grass and legume leaves. Greater herbage accumulation occurred for signalgrass submitted to full sun (57 kg ha–1 d–1) than under shade (27 kg ha–1 d–1) (p = .0006). Morphometric measurements of tree regrowth did not show differences for total leaf mass (p = .8603) and mass of thick stems (p = .6157) between tree legume species. Gliricidia leaf IVDOM was greater (504 g kg–1) than sabiá leaf IVDOM (315 g kg–1) (p < .0001). Nitrogen concentration was greater in leaves (p = .0007), fine stems (p = .0050), and thick stems (p = .0333) of gliricidia throughout the evaluated period when compared to the same fractions of sabiá. Both tree species, at the densities employed in this study, affected negatively and to a similar extent the herbage accumulation of signalgrass.