In tropical areas of Mexico, Leucaena leucocephala is widely used in silvopastoral systems. However, little information exists on other native woody species of high forage potential, such as Guazuma ulmifolia. The aim of this study was to evaluate the components of biomass, forage yield and quality, and availability of N in fodder banks of L. leucocephala, G. ulmifolia, and a mixture of both species during dry and rainy seasons, under sub-humid tropical conditions. The experimental unit was a 5 9 10 m plot, containing three rows with 2 m between rows; each row had 20 plant positions with 0.50 m between plants.Within each plant position therewas either a single plant, in the case of purecrop, or two plants, in the case of mixed of both species. A complete randomized block design with three repetitions was used. In both seasons, therewere a significantly greater proportion of leaves in the G. ulmifolia fodder banks (71 %) and in mixed fodder banks (69 %) than in L. leucocephala fodder banks (64 %). Consequently, these systems had leaf-to-stem ratios of 2.4, 2.2 and 1.9, respectively. Inglés

The forage yield of fodder banks was not influenced by season. Themixed fodder bank had greater forage yield (5.1 t DM ha-1) than the L. leucocephala fodder bank (3.4 t DM ha-1) in each season. Additionally, the mixed fodder bank accumulated more forage yield during the experimental period (10.2 t DM ha-1 - year-1) than G. ulmifolia (9.0 t DM ha-1 year-1) or L. leucocephala (6.9 t DM ha-1 year-1). The concentrations of CP, C and C:N were not influenced by season. Forage NDF and ADF concentrations were greater in the rainy season (476 g kg-1 DM) compared with the dry season (325 g kg-1 DM). Mixed fodder banks had the greatest N yield (185.9 kg ha-1) and consequently the greatest availability of N (371.8 kg N ha-1 year-1). We conclude that mixed fodder banks of L. leucocephala and G. ulmifolia are a better option for improving productivity and forage quality in comparison with pure fodder banks in Yucatan, Mexico. Inglés