Formas de fósforo no solo e eficiência nutricional do meloeiro em função da adubação mineral e orgânica

Abstract

The phosphorus is one of the most applied nutrients in Brazilian agriculture and its availability and forms in soil are affected by fertilization. Melon plants are demanding in phosphorus and associated to the low natural fertility of the soils, it is justified the studies to increase the productivity of the fruits. The objective of this study was to evaluate the effects of mineral and/or organic fertilization on the efficiency of macronutrient utilization, accumulation, partition, partial balance of phosphorus (P) and the distribution of phosphorus fractions in the soil during the growth cycle of Goldex F1 hybrid melon. The experiment was carried out at the Experimental Field of the Pacajus, belonging to Embrapa Tropical Agroindustry, on soil that classified as Ultisol. The experimental design was in randomized blocks in split-plot, the fertilizers application as main treatments (mineral fertilization, bovine manure, bovine manure + mineral fertilization, poultry liiter and poultry litter + mineral fertilization) five soil sampling in the subplots (before seedlings planting, early flowering, early fructification, fruit growing and fruit harvest), with four replicates. Every sampling, plants were collected, separated in shoots and roots and then in immature and mature fruits, to obtain the dry matter and chemical analysis. The technique of sequential fractionation of phosphorus was used for the determination of the organic and inorganic forms and later, the separation of these in compartments according to lability: P-Labile; P-Moderately labile and P-non labile. The partition of the phosphorus in the shoots (leaves, stems and flowers) and fruits (immature and mature) showed that about 80% of the P is destined for the fruits. There was no significant difference between treatments for macronutrient use efficiency. The contents of the most labile forms of phosphorus were influenced by the fertilization and there was a decrease of these fractions throughout the cultivation of the melon. The labile and moderately labile forms of P had about 80 % of the soil Total-P. The organic forms of P had an important contribution in the availability and maintenance of labile forms of P in the soil. The association of fertilizers (mineral and organic) was configured in the best form of phosphate fertilization for melon. The fertilization and the time of cultivation of the melon alter the distribution and proportion of the forms of phosphorus in the soil.