ABSTRACT The use of saline water in agriculture has increased in the Brazilian semiarid due to low availability of good quality water for irrigated agriculture, being the selection of salt tolerant hybrids an alternative to reduce the effect of salinity on nutritional status of plants. So, the objective of this work was to evaluate the effect of salinity of irrigation water in the accumulation and partition of nutrients in the vegetable tissue of watermelon cultivars, in the region of Mossoro in the State of Rio Grande do Norte, Brazil. The treatments studied consisted of applying irrigation water with five electrical conductivities (EC1 = 0.57, EC2 = 1.36, EC3 = 2.77, EC4 = 3.86 and EC5 = 4.91 dS m-1), two watermelon cultivars and four samplings times (15; 29; 43 and 60 days after transplanting), arranged in a scheme of split plot(5x2x4) and outlined in complete blocksrandomized with four replications. The accumulated nutrients in plants were influenced by ECw, occurring a loss in comparison with the higher ECw of 24.1 and 36.4% in the accumulationof N and P in the vegetative part of plant and 37.8 and 30.1 % in the accumulation of P and K in the aerial part. The accumulation of N, P and K in the watermelon was influenced by plant age, with reduction at the end of the cycle.

O uso de águas salinas na agricultura é um dos principais fatores que limitam a produção e a qualidade dos frutos no Estado do Rio Grande do Norte, sendo a seleção de híbridos tolerantes à salinidade e a utilização de adubação nitrogenada, alternativas para se evitar perdas de rendimento e qualidade desses frutos. Assim, o objetivo com este trabalho foi avaliar o comportamento produtivo e a qualidade dos frutos de três cultivares de melancia (Quetzali, Shadow e Leopard) submetidas a diferentes salinidades da água de irrigação e doses de nitrogênio, na região de Mossoró, RN. Os tratamentos consistiram em aplicação de água de irrigação com cinco condutividades elétricas (0,57; 1,36; 2,77; 3,86 e 4,91 dS m-1) e três doses de nitrogênio (48, 96 e 144 kg ha-1), delineados em blocos casualizados, com quatro repetições. Foram avaliados a produtividade, o número e o peso médio dos frutos e o teor de sólidos solúveis. O peso médio e o número de frutos influenciaram as perdas de rendimento das cultivares de melancia estudadas; apenas a cultivar Shadow apresentou o teor de sólidos solúveis dos frutos alterado com a salinidade da água de irrigação.

The use of saline waters in the agriculture is one of the main factors that limit the production and the fruit quality in the State of Rio Grande do Norte, being the selection of tolerant hybrids to salinity and the use of the nitrogen fertilization, alternatives to avoid losses in income and quality of the fruits. Therefore, the objective of this study was to evaluate the production and the quality of the fruits of three cultivars of watermelon (Quetzali, Shadow and Leopard) under different salinities of irrigation water and doses of nitrogen in the region of Mossoró, RN. The treatments consisted in the application of irrigation water with five electrical conductivities (0.57; 1.36; 2.77; 3.86 e 4.91 dS m-1) and three doses of nitrogen (48, 96 e 144 kg ha-1), delineated in randomized blocks, with four replications. The productivity, the number and the mean weight of fruits, as well as the content of soluble solids were evaluated. The mean weight of fruits and the number of fruits affected the loss of income of studied watermelons cultivars. Only the Shadow cultivar had the soluble solids content of fruits altered with the salinity of irrigation water.