AGRONOMIC RESPONSE OF RICE CROP UNDER EFFECT OF ROCK PHOSPHATE DOSES

Abstract

Phosphorus (P) is an important nutrient for rice crop productivity. However, low fertilization efficiency occurs in Tocantins soils, and the increase in input costs makes natural phosphates an economical alternative. The objective of this work was to evaluate agronomic characteristics in rice (Oryza sativa) under the effect of doses of reactive natural phosphate. The experiment was carried out in a greenhouse between January and April 2020. The treatments consisted of four doses of phosphate rock and two additional controls (Phosactiv^® and triple superphosphate), conducted in a completely randomized experimental design, with four replications. The experimental units consisted of pots with a capacity of 10 dm^-3, where five rice seeds were sown per pot, cultivar IRGA-424, thinning to obtain two plants per pot. Plants height were evaluated; the mass of grains per plant; the number of panicles per plant, the number of tillers per plant and the number of grains per panicle. In addition, P content was evaluated by Mehlich (P-meh) and resin (P-res) methods, in addition to pH and calcium content (Ca). It was found that phosphate rock exerted a greater influence on plant height and the number of grains per panicle in rice, at doses of 295,62 and 300 kg ha^-1 compared to commercial natural phosphate. Reactive natural phosphate increased more P in the soil than simple superphosphate at the same tested dose.