Arboreal Legume Litter Nutrient Contribution to a Tropical Silvopasture
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2016 by the American Society of Agronomy. Legumes contribute to pasture sustainability through symbiotic N2 fixation, which may increase primary productivity and animal performance in low-input systems. Litterfall is the main way of cycling nutrients from tree legumes. We quantified gliricidia [Gliricidia sepium (Jacq.) Kunth ex Walp.] and sabi (Mimosa caesalpiniifolia Benth) litter deposition, along two 336-d cycles, in a signalgrass (Brachiaria decumbens Stapf.) pasture. Litterfall was produced throughout the year but concentrated in the dry season. Sabi produced slightly greater (P < 0.0001) litterfall amounts in the two cycles (10,790 kg ha1) than gliricidia (10,420 kg ha1) but the overall average N concentration of gliricidia (21.5 g kg1) was greater than that of sabi (18.8 g kg1). Nitrogen amounts cycled through the litter were greater for gliricidia in both cycles (105 and 109 kg N ha1) than for sabi (87 and 98 kg N ha1). The proportions of litter N that were derived from the atmosphere by symbiotic fixation were similar (P 0.05) in both species (55%) and varied little along the two cycles. Lignin concentration, which influences decomposition, was similar in both species, averaging 238 and 214 g kg1 in the two cycles for gliricidia and 233 and 246 g kg1 for sabi. Greater N concentration, lower C/N ratio and lower lignin concentration indicate that gliricidia litter may have a faster cycling rate than sabi litter. Sabi could be a more promising species for soil cover and protection because of its slower litter decomposition rate.