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Arboreal Legume Litter Nutrient Contribution to a Tropical Silvopasture

2016; Wiley; Volume: 108; Issue: 6 Linguagem: Inglês

10.2134/agronj2016.02.0120

1435-0645

Valéria Xavier de Oliveira Apolinário, José Carlos Batista Dubeux, M. A. Lira, Everardo Valadares de Sá Barretto Sampaio, SILVANIA O. DE AMORIM, Nalígia Gomes de Miranda e Silva, James P. Muir,

Ruminant Nutrition and Digestive Physiology

Legumes contribute to pasture sustainability through symbiotic N 2 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 sabiá ( 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. Sabiá produced slightly greater ( P < 0.0001) litterfall amounts in the two cycles (10,790 kg ha −1 ) than gliricidia (10,420 kg ha −1 ) but the overall average N concentration of gliricidia (21.5 g kg −1 ) was greater than that of sabiá (18.8 g kg −1 ). Nitrogen amounts cycled through the litter were greater for gliricidia in both cycles (105 and 109 kg N ha −1 ) than for sabiá (87 and 98 kg N ha −1 ). 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 kg −1 in the two cycles for gliricidia and 233 and 246 g kg −1 for sabiá. Greater N concentration, lower C/N ratio and lower lignin concentration indicate that gliricidia litter may have a faster cycling rate than sabiá litter. Sabiá could be a more promising species for soil cover and protection because of its slower litter decomposition rate. Core Ideas Litter deposition was an important pathway of N return in warm‐climate silvopasture systems. Tree legumes added significant amounts of biological nitrogen fixation to silvopasture systems. Gliricidia litter presented better quality than Mimosa litter. Proportion of litter N derived from atmosphere was significant.