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This article in CS

  1. Vol. 52 No. 3, p. 1416-1423

    * Corresponding author(s): j-muir@tamu.edu


Signal Grass Litter Decomposition Rate Increases with Inclusion of Calopo

  1. Hiran Marcelo Siqueira da Silvaa,
  2. José Carlos Batista Dubeuxa,
  3. Mércia Virginia Ferreira dos Santosa,
  4. Mário de Andrade Lirab,
  5. Mário de Andrade Liraa and
  6. James P. Muir *c
  1. a Federal Rural University of Pernambuco – UFRPE. Av. D. Manoel de Medeiros, s/n, Recife, Pernambuco
    b Pernambuco State Agricultural Institute – IPA, Av. General San Martin, 1371, Recife, Pernambuco, 50761-000
    c Texas AgriLife Research, Stephenville TX 76401


Low N availability is a major limitation in tropical and subtropical pasture systems and one of the main causes for system degradation. Including legumes in forage mixes may enhance soil-N presence and cycling, therefore mitigating the problem. To test this theory, signal grass [Brachiaria decumbens (Stapf) R. D. Webster] litter chemical composition and decomposition after inclusion of calopo (Calopogonium mucunoides Desv.) at 0, 50, or 100% of litter mass was evaluated. Litter samples were collected from both species and incubated by litter bag technique for 0, 4, 8, 16, 32, 64, 128, or 256 d in 2007 and 2008. Biomass decomposition was described by a simple exponential organic matter (OM) decay model (p < 0.0001; Y predicted [the remaining biomass at a given time of decomposition, predicted by the single exponential model] = 91.11–0.00451t and 94.16–0.00217t for year 1 and 2, respectively). Remaining biomass was lower (p < 0.05) in 2007 (28%) than 2008 (54%) following 256 d incubation at least in part because of greater lignin concentrations in 2008 litter. Pure signal grass litter C:N values were 74 to 76% greater (p < 0.05) than pure legume while the inclusion of 50% calopo reduced (p < 0.05) grass ratios by 62 to 64%. Net annual N mineralization increased (p < 0.05) from 27% without legume to 38% with legume inclusion at 50% of the grass litter, a nutrient cycling acceleration of 16% (p < 0.05). This research indicated that the inclusion of calopo will ameliorate N deficiency in soils of a signal grass pasture.

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