Estimación de la fijación de nitrógeno en una vega de Tierra del Fuego por el método de la diferencia de nitrógeno

Abstract

Sheep production in Tierra del Fuego is based on extensive grazing of largely native pastures. Production systems focus on meeting the nutritional demands of all classes of sheep from these pastures throughout the year, but there are deficit periods when production is limited by pasture quality and avai lability. Legumes are the cheapest sources of protein for animals on these grasslands and could be a key component of production systems. There are no published measurements of nitrogen fixation from this region of southern Patagonia. In a field experiment on a meadow located on dryland steppe (300–350 mm year -1 ) in Tierra del Fuego (53°09’south; 68°44’west), grazing exclusion cages were used in established reseeds (on wet and dry areas) to measure the yield and nitrogen fixation of Trifolium repens during the growing season. The nitrogen difference method was used to measure fixation and the experimen tal design was randomized block analysis with three replicates. The model included area as sources of variation, analysed by analysis of variance. The mean level of nitrogen fixation was 98.7 kg N ha -1 and significantly more (P ≤0.05) nitrogen was fixed on wet areas (126 kg N ha -1 ) than dry areas (71 kg N ha -1 ).