Efeito de zeólita e fontes alternativas de potássio e fósforo no cultivo de girassol ornamental (Helianthus annuus L.)

Abstract

Potassium and phosphorus are essential to plants. The use of alternative sources of these nutrients, associated with soil conditioners, is very important for agriculture as they improve soil quality favoring the cultivation and reducing dependence on imported sources of these nutrients. The aim of this work was to evaluate the effect of vinasse and Bayóvar rock phosphate as alternative sources of potassium and phosphorus, respectively, and coarsely- and finely-grinded zeolite, as soil conditioner for cultivating ornamental sunflower. The experiment followed a completely randomized 4x3 factorial design, with four potassium and phosphorus sources (potassium chloride and ammonium phosphate, vinasse and ammonium phosphate, potassium chloride and Bayovar rock phosphate, and vinasse and Bayovar rock phosphate) and three zeolite conditions (without zeolite, with finely-grinded zeolite and with coarsely-grinded zeolite) with one plant per pot and four replicates per treatment. The number of leaves, height and diameter of stems, internal diameter of inflorescence, and dry matter of leaves, stems, inflorescence and total were evaluated. After plant harvesting, water was applied at 15, 20 and 50 mm every five days. The leachate was collected after the third water application, and its volume and ion concentration were measured. After leaching test, soil fertility was evaluated from each pot. In general, soil fertility was improved in the presence of zeolite, not interact with fonts potassium chloride and ammonium phosphate, and ammonium phosphate and vinasse. When neither zeolite nor vinasse were applied, Bayovar rock phosphate showed a better performance as P source. Vinasse treatments did not differ from potassium chloride ones, which indicates its potential as K+ source. Finely-grinded zeolite promoted efficient retention of K+, Ca2+ and Mg2+, which prevented these nutrients from leaching. Moreover, in vinasse treatments there were less leaching of K+.