Fosfatos naturais reativos e calcinados na fosfatagem da cana-de-açúcar

Abstract

Tropical soils have high acidity, low base saturation, and low availability of nutrients such as phosphorus (P). The P supplied in fertilization becomes gradually unavailable due to adsorption to the soil, which generates recommendations for high doses of P, increasing production costs. Thus, alternative sources of P are researched, as they have been shown to be able to compete with conventional sources in efficiency and cost. This study aimed to evaluate the agronomic efficiency of P sources applied to the total area before sugarcane planting. Six phosphorus sources were used at a dose of 100 kg ha-1 of P2O5: FNR OCP Heringer, FNR OCP Heringer plus humic acid, granulated and crumbly calcined thermophosphate, Phosphate Itafós and FNR Bayovar. Additional doses were established for: granulated calcined thermophosphate (50, 150, 200 kg ha-1 P2O5) and bran (150 kg ha-1 P2O5); FNR OCP Heringer (50, 150 and 200 kg ha-1 P2O5); another treatment without phosphating was added. The availability of Ca, Mg, P and Si for the soil and plants, the effect on sugarcane yield and quality and the accumulated production were evaluated. The calcinedgranulated spreadable thermophosphate showed superior results compared to the other phosphate sources for sugarcane biometry. The production of stalks and sugar were not affected by the doses of calcined thermophosphate or OCP reactive rock phosphate in both places, for any of the evaluated cuts. The application of thermophosphate generates positive results for the soil and sugarcane; however, not all thermophosphate application conditions will generate results significantly superior to other sources or to the control treatment.