Limestone and phosphorus application and forage production in natural pastures with sodseeding of cool-season species

Natural pastures are important ecosystems that both contribute to biodiversity conservation and provide an important source of income, especially for cattle ranchers. While these pastures yield fairly low productivity, they can be improved by increasing soil fertility and introducing species with high productive potentials. In this sense, the purpose of this study was to evaluate the effects of applying limestone and phosphorus, as well as introducing cool-season species with a mixture of species dominated by Schizachyrium tenerum Nees, into a natural pasture in the Catarinense Plateau. The experiment was conducted from January 2010 to December 2013; the treatments consisted of superficial distribution of limestone in proportions of 3.6, 7.2, 11.0, and 14.4 t ha(-1), as well as distribution of phosphorus in the form of triple superphosphate in proportions of 35, 70, 105, and 140 kg of P2O5 ha(-1). In addition, cool-season species were overseeded. The experiment consisted of a randomized block design with subdivided plots and three replications. Limestone was applied to the main parcel, whereas phosphorus was applied to the subplots. There was no interaction between the levels of limestone and phosphorus. The application of 11.0 t ha(-1) of limestone yielded the highest forage production, with 3,932.2 kg of dry matter (DM) ha-1 during the second year. Red clover was the species that best reacted to the additions, with levels of 7.2 and 11.0 t ha(-1) over the 4 years. In addition, phosphorus provoked a positive response throughout the experiment. The highest forage production was observed during the second year, with an addition of 140 kg P2O5 ha(-1) (4,419.4 kg DM ha(-1)). Only one-eighth of the recommended amount of limestone (3.6 t ha-1) allowed for the establishment and persistence of the legumes introduced into natural pastures. These additions, associated with increasing levels of phosphorus, yielded linear growth in the production of forage in natural pastures with a mixture of species dominated by Schizachyrium tenerum Nees.