Avaliação da disponibilidade de fósforo e recomendação de adubação fosfatada para cana-planta em solos do estado de Pernambuco

Abstract

Despite concerns with expected production, the phosphate fertilizer recommendation for Pernambuco lacks of the soil buffer capacity influence on P availability. Therefore, this work had as objective to 1) evaluate the maximum agronomic end economic influence of phosphate fertilizer in sugarcane, considering content and quality of clay fraction; 2) relate physical, chemical and mineralogical soil characteristics with critical levels of P in soil and plant; 3) study extraction methods for estimate P availability; 4) evaluate P allocation to determine P extraction and export; 5) present a proposal to bring up to date interpretation and recommendation of phosphate fertilizer for sugarcane in the State of Pernambuco. The experiments were carried out in field conditions atZona da Mata of sugarcane cropping area of the State, where intemperate soils with different mineralogical, chemical and physical composition are predominant. Five soils were used: Argissoil Yellow distrocoeso (PAdx); Latossoil Yellow distrofic (LAD); Argissoil Yellow distrofic (PAd); Gleissoil haplic eutrofic (GXVe); and Espodossoil carbic duripanic (ESKo). The soils were chemically, physically and mineralogical characterized. The treatments consisted of seven doses of P, determined in function of the P maximum capacity of adsorption (PMCA). The experimental design was a completely randomized block, with four replicates, totalizing 28 experimental units. In soil samples collected after treatment application, P was determined by Mehlich-1, Mehlich-3, Bray-1 and Anionic Change Resin (ACR) extractors. The vegetal material was collected, sampling four plants from each one of the three central lines of the utile experimental unit, totalizing 12 plants per plot. Plants were separated into pointers, leaves, stems and senescent leaves. Number of plantby linear meter and stem height to “colon” of the leaf (+1) were also evaluated.Agricultural (TCH) and industrial (TAH) productivity along with the technological data BRIX, POL, PUREZA, FIBRA, PCC E ATR were determined. Mehlich-1 and ACR were the extractors that most correlated with both P absorbed and accumulated by sugarcane. However ACR did not present correlation with any physical or chemical characteristics of the soils, having extracted P indistinctly,and independent of the soil. The critical levels of P in soil and plant were dependents on the soils phosphate buffer power, when the extractor for evaluation of the available was Mehlich-1. The critical levels of P in soil determined by ACR correlated with the critical levels of P in plants significantly but they were not dependent on any chemical or physical characteristic of the soils. The critical levels of P in soils determined by Bray-1 and Melhich-3 did not correlate with PCMA, neither did they with critical levels in plants.Phosphate fertilizer influenced TCH and TAH positively. Therefore, it was possible to establish a suggestion for phosphate fertilizer interpretation and recommendation for Pernambuco State based on soil clay content or value of reminiscent P, when the extractor for estimating the available P in soil was Mehlich-1. It was also suggested the use of ACR as extractor for evaluating P availability to soils of Pernambuco, including a proposal for interpretation of P content available in the soil through RTA and for recommendation of phosphate fertilization.