Vegetation cover, biomass and protein content of the herbaceous layer of a savannah environment in Maracanã district, Pará state, Brazil

Abstract

Low nutrient content found in natural grasslands does not meet the nutritional requirements of cattle, and this turns out to be one of the main reasons for low yield of cattle farming in savannah environments. In this context, this study evaluates vegetation cover, biomass and protein content of herbaceous plants of a savannah environment in the eastern Amazon region to explore its potential as pasture during the annual cycle. The study area was a savannah enclave (2.500 ha) in Maracanã district, Pará, Brazil. Four plots of 10 × 100 m were inventoried in four-month intervals during two years. Within each plot, biomass was determined by harvesting above-ground parts of plants from five sub-plots of 1 m2, yielding a total of 20 samples per campaign. The biomass was sorted into three categories: 1. Axonopus polydactylus; 2. Axonopus aureus; 3. other species. Within each plot, the above-ground parts were harvested and the sampled material was oven-dried, weighted and its protein content determined. The Poaceae family accounted to 63 % of the total vegetation cover, being mainly represented by the species Axonopus polydactylus and Axonopus aureus. The biomass and protein content varied with season, yielding highest values during the rainy season and lower values during the dry season. The vegetation analysed is not recommended for use as pasture for extensive cattle farming, as biomass production and protein content stayed below the required minimum values for cattle nutrition.