Phosphate fertilization influences macronutrient accumulation in watermelon cv Magnum

ABSTRACT Studies on nutrient uptake are important to understand nutritional needs of crops, which demand may also be influenced by fertilization management, particularly P fertilization. Thus, the aim of this study was to evaluate macronutrient accumulation and distribution in watermelon cv. Magnum, under two forms of phosphate fertilization. The experiment was carried out in a sandy-textured Argisol in Mossoró-RN. The experimental design was a randomized block design, arranged in split plot in time, with four replicates. We evaluated dose of 137 kg ha-1 of P2O5 under two forms of fertilization [pre-planting (F0) and pre-planting + topdressing (F1)]. Triple superphosphate (SFT) was used for pre-planting applications and topdressing applications were done through fertigation using monoammonium phosphate (MAP, 34 kg ha-1 of P2O5). Shoot samples (stem + leaf + fruit) of the experimental plots were collected at 27, 34, 40 and 55 days after emergence (DAE), and quantitative values of the accumulated nutrients were determined. In general, the highest accumulation of macronutrients occurred in the last third of the crop cycle. General accumulation of macronutrient was altered by fertilization form. An increase in P accumulation was observed using F1 fertilization, both in total and in fruits. Macronutrient accumulation rates increased during the evaluation period, except for Ca and Mg in F1 fertilization. F1 fertilization provided higher total accumulations of Ca and Mg, but the same did not occur for the accumulation in fruits. RESUMO Estudos de marcha de absorção de nutrientes são importantes para a definição das necessidades nutricionais das culturas, cuja demanda pode também ser influenciada pelo manejo da adubação, particularmente no caso do P. Assim, objetivou-se com este trabalho avaliar a marcha de acúmulo de macronutrientes da melancieira cv. Magnum irrigada submetida a duas formas de adubação fosfatada. O experimento foi realizado em Argissolo de textura arenosa, em Mossoró-RN, no delineamento experimental de blocos casualizados com parcelas subdivididas no tempo, com quatro repetições. Foi avaliada a dose de 137 kg ha-1 de P2O5 sob duas formas de adubação [em pré-plantio (F0) e em pré-plantio + cobertura (F1)]. Superfosfato triplo (SFT) foi utilizado para as aplicações em pré-plantio e, as aplicações em cobertura foram feitas através de fertirrigação, utilizando fosfato monoamônico (MAP, 34 kg ha-1 de P2O5). Foram realizadas coletas aos 27, 34, 40 e 55