The effect of sources and levels of phosphorus and lime for forrage pasture fertilization in Rio Grande do Sul

Abstract

During the 1979/1982 period, the effect of sources, levels of phosphorus and lime, on winter improved pasture was studied in different soils, classified as: Vertic Planosois (Argiaquoll), Hydromorfic Vertisol (Argiaquoll), Lateritic Red-Brown Eutrophic Soil (Paleudalf) and Dystrophic Lithosol (Haplumbrept). During four years  in four different sites, the effect of three sources of phosphorus (Triple superphosphate, Gafsa  phosphate and Marrocos phosphate) and six levels (0, 50, 100, 150, 200, 250 kg/ha of P₂O₅ ), with and without lime applied on winter improved pasture was studied. At the year of the pasture establishment, triple superphosphate was more efficient in dry matter production only on the Lateritic Red-Brown Eutrophic soil. At the end of the experiment, differences among sources of phosphorus were not detected. The best levels of applied phosphorus ranged from 100 to 250 kg/ha of P₂O₅. In most soils, liming had a long-term effect. Sources, levels of phosphorus and lime did not affect the botanical composition of pastures nor its mineral content in N, P and K, but it was associated to higher increase of dry matter production. There was a larger potassium plant uptake on lime treatments; meanwhile, a decrease in the amount of K in the soil was observed.