Litter decomposition of Brachiaria decumbens Stapf. and Calopogonium mucunoides Desv. in the rumen and in the field: a comparative analysis

Abstract

Litter deposition and decomposition are important components of the nutrient cycling process in grasslands. Litter decomposition studies in the field are tedious and time-consuming. Finding an approach to speeding up research would therefore be a major advancement in the field. In this study, a comparative analysis of the litter decomposition process of signal grass (Brachiaria decumbens Stapf.) and calopo (Calopogonium mucunoides Desv.) in two distinct environments (field vs. goat rumen) was carried out. Two incubation trials were performed. In the first trial litter of both plant species was incubated in the rumen of fistulated goats using the in situ technique. Second trial, litter samples were incubated on signal grass pastures using the litter bag technique. Litter samples of signal grass and calopo were incubated by different periods in the rumen (0, 6, 12, 24, 48, 96, and 144 h) and in the field (0, 4, 8, 16, 32, 64, 128, and 256 days). At the end of the incubation period, the remaining biomass of signal grass was similar between rumen and field (*38%), but calopo decomposed more extensively in the field. The C:N ratio was considered high for signal grass (*100) at the beginning of the experimental period. Calopo showed initial C:N ratio of 29. Nitrogen was more extensively decomposed in the rumen as opposed to the field; however, despite several differences in terms of environment and time of incubation, remaining biomass at the end of incubation was similar between rumen and field trials, suggesting common limits for decomposition in both environments. Decomposition models, however, showed different relative decomposition rates (k) along the incubation period. As a result, the use of the rumen model to simulate field decomposition cannot be recommended.

Deposition and Decomposition of Signal Grass Pasture Litter under Varying Nitrogen Fertilizer and Stocking Rates

“…These pastures are typically established in areas with poor soil fertility and are rarely fertilized. The C 4 grass litter deposited under these circumstances often has high lignin concentration and high C/N ratio (Silva et al, 2010). Combining low soil fertility, litter resistant to decomposition, and no fertilization may result in immobilization of soil nutrients and poor pasture productivity (Boddey et al, 2004).…”