Effects of Phosphorus Fertilizer Solubility on Pastures Yield and Quality in Andisols

Phosphate rock (PR) and triple superphosphate (TSP) are options for phosphorus (P) fertilization of crop and pasture production systems. However, to our knowledge, no studies have compared P sources with different solubilities in field trials to date. The aim of this study was to compare the effect of PR and TSP on forage yield, P uptake and nutritive quality of pastures growing in Andisols. Three experiments were conducted in southern Chile, analysing the factorial combination of two P sources (PR and TSP) and four P rates (0–328 kg P ha−1). Results showed that cumulative dry matter production in year 1, year 2 and total was significantly (p ≤ 0.05) affected by P dose, time of cut and the interaction of both variables, indicating that PR is as effective as TSP in acid soils. The treatments did not show significant differences among themselves (p ≥ 0.05) in foliar P concentration, P uptake, P apparent recovery efficiency and nutritive quality of pastures evaluated. The highest P apparent recovery efficiency was obtained with 22 kg P ha−1 and 44 kg P ha−1 independent of the phosphate fertilizer applied. A P demand factor of 2.7–3.1 kg P Mg−1 dry matter was estimated. All these information will be useful to improve P fertilization managements of pastures growing in Andisols.