Publication Date

1993

Description

Five tropical grasses; Brachiaria brizantha cv. Marandu, B, decumbens cv. Basilisk, Panicum maximum cv. Coloniilo, P. maximum cv, Tobiatil, P. maximum cv. Tanzania-I, were planted on a dark red latosol (Oxisol) and grazed for 3 rainy and 3 dry seasons . The original savanna vegetation was removed, the soil cultivated and fertilised with 1000 kg/ha of dolomitic limestone, 350 kg/ha of single superphosphate, 100 kg/ha of KCI and 40 kg/ha of fritted traced elements. Treatments were arranged in a RCB design with 3 replicates. Paddocks were 1.5 ha. Grazing pressure was adjusted to approximately 8 or 15 kg of total dry matter (DM) of pasture on offer/100 kg of live weight in Pan/cum cultivars and Brachiaria species, respectively. Plant samples were collected monthly simulating animal grazing (plucked by hand). Nutrient concentration of N, P, K, Ca, Mg and S were analysed on a DM basis. General trends showed decreasing plant tissue concentration of all elements in the 5 species with the exception of Ca and Mg, which had a slight increase with time. Phosphorus content was the most significant parameter associated with green DM (leaf+stem) which in turn was the best predictor of animal daily gain. Pan/cum cultivars were more sensitive to phosphorus decline (1.83-0.93 g/kg) than Brach/aria species (1.45· 1.00 g/kg), Nutrient concentrations were highly associated with rainfall pattern, and maximum level of most elements occurred, regardless of year, 30-40 days after the start of the opening rains.

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Seasonal Changes in the Chemical Composition of Cultivated Tropical Grasses in the Savannas of Brazil

Five tropical grasses; Brachiaria brizantha cv. Marandu, B, decumbens cv. Basilisk, Panicum maximum cv. Coloniilo, P. maximum cv, Tobiatil, P. maximum cv. Tanzania-I, were planted on a dark red latosol (Oxisol) and grazed for 3 rainy and 3 dry seasons . The original savanna vegetation was removed, the soil cultivated and fertilised with 1000 kg/ha of dolomitic limestone, 350 kg/ha of single superphosphate, 100 kg/ha of KCI and 40 kg/ha of fritted traced elements. Treatments were arranged in a RCB design with 3 replicates. Paddocks were 1.5 ha. Grazing pressure was adjusted to approximately 8 or 15 kg of total dry matter (DM) of pasture on offer/100 kg of live weight in Pan/cum cultivars and Brachiaria species, respectively. Plant samples were collected monthly simulating animal grazing (plucked by hand). Nutrient concentration of N, P, K, Ca, Mg and S were analysed on a DM basis. General trends showed decreasing plant tissue concentration of all elements in the 5 species with the exception of Ca and Mg, which had a slight increase with time. Phosphorus content was the most significant parameter associated with green DM (leaf+stem) which in turn was the best predictor of animal daily gain. Pan/cum cultivars were more sensitive to phosphorus decline (1.83-0.93 g/kg) than Brach/aria species (1.45· 1.00 g/kg), Nutrient concentrations were highly associated with rainfall pattern, and maximum level of most elements occurred, regardless of year, 30-40 days after the start of the opening rains.