ABSTRACT
Summary A small-plot experiment was conducted during 2 consecutive years in the cerrados of Brazil to evaluate the effect of four dates of deferment (21 February, 7 and 21 March, and 4 April, respectively) on rate of growth, chemical composition, and in-vitro dry-matter digestibility (IVDMD) of a pure stand of Galactia striata, a naturalized legume. The chosen dates of deferment embraced the last 2 months of the rainy season. Yields were estimated at intervals of 28 days, over an experimental period of 237 days, ending with the beginning of the following rainy season. Asymptotic growth was observed throughout the experimental period. Yields during the critical August-September period ranged between 1,000 and 5,000 kg dry matter (DM)/ha, depending on treatment and year. Differences in yield between treatments and years were accounted for largely by differences in accumulated rainfall and maximum temperature, as was indicated by regression analysis. The contribution of leaves to dry-matter yield decreased from an initial 75% to about 35% at 168 days of age. This decrease was treatment-independent and strongly age-dependent. During most of the dry season, crude protein (CP) averaged 15% in the standing herbage; no treatment effect was noted when treatments were compared at the same age. Crude protein (CP) in leaves decreased from 32% at 28 days of age to about 20% at 112 days and remained constant thereafter. In the stems, CP was 15% initially, and it stabilized at 10% at 84 days. The IVDMD of the available forage fell very slowly during the dry season; in the most critical period it varied between 55% and 60%. In leaves, the IVDMD fell initally but soon stabilized around 65% at 56 days. Seed production was observed in the earliest dates of deferment, and it amounted to up to 280 kg/ha. It was concluded that galactia is capable of providing high-quality forage during the dry season and that its yield depends mainly on the precipitation and temperature accumulated after the date of deferment.
