Nutritional status of cotton plants under fertigation with reuse water and phosphate fertilization/Estado nutricional do algodoeiro fertigado com agua de reuso e adubacao fosfatada

Water reuse is an important practice in water resource management especially in arid and semiarid areas. The objective was to evaluate the mineral composition and boll weight of upland cotton (cultivar BRS 335) plants under fertigation with domestic sewage effluent and phosphate fertilization. An experiment was carried out using randomized block design in a 3 * 2 factorial scheme with six repetitions. Cotton plants were fertigated with three fertigation solutions containing domestic sewage effluent (RW) and supply water (SW) in the proportions of 100% SW - [T.sub.1], 50% SW + 50% RW - [T.sub.2] and 100% RW - [T.sub.3], and two phosphate fertilizer managements (with and without phosphate fertilization at pre-planting). Macronutrient and micronutrient concentrations in the shoots and boll weight were measured and evaluated. Fertigation utilizing reuse water is able to supply both water and part of the nutritional demand of cotton plants. Calcium, copper, iron and zinc concentrations in cotton leaves were below the optimum range for the crop. Reuse water did not meet the total requirements of Ca, Cu, Fe and Zn of cotton, so complementary mineral supplementation with these nutrients is recommended for the crop to obtain high yield. Key words: Gossipyum hirsutum, water reuse, semi-arid region, foliar diagnosis O reuso de agua e uma pratica importante no gerenciamento dos recursos hidricos, especialmente nas zonas aridas e semiaridas. Com isso, objetivou-se avaliar o estado nutricional e a massa do capulho do algodoeiro herbaceo (cultivar BRS 335) quando fertigado com efluente de esgoto domestico e adubacao fosfatada. Um experimento foi conduzido em delineamento de blocos ao acaso, em esquema fatorial 3 * 2, com seis repeticoes. As plantas de algodao foram fertigadas com tres solucoes contendo efluente de esgoto domestico (AR) e agua de abastecimento (AA) nas proporcoes de 100% de AA - [T.sub.1], 50% AA + 50% AR - [T.sub.2] e 100% AR - [T.sub.3] e, dois manejos da adubacao fosfatada (com adubacao e sem adubacao fosfatada em pre-plantio). Foram avaliados os teores de macronutrientes e micronutrientes nas folhas e a massa de capulho. A fertigacao com agua de reuso e viavel para suprir a demanda hidrica e parte da demanda nutricional do algodoeiro. A agua de reuso nao atendeu aos requisitos totais de Ca, Cu, Fe e Zn do algodao, portanto, recomenda-se a suplementacao mineral complementar com esses nutrientes para que a cultura obtenha alto rendimento. Palavras-chave