Viabilidade agroeconômica do uso de água salina no cultivo do meloeiro.

Abstract

In Brazil, the State of Rio Grande do Norte is the greatest producer of melons for exportation and the farmers use irrigation waters of different salinities (ECw). The melon plant is one of the most demanding cucurbitacea with regard to the fertilizers. The most extracted macronutrient for the melon is potassium, which has important action in the fruits due to its role in the translocation of carbohydrates. With the objective of studing the response on soil characteristics and on growth, yield and production quality o f two melon cultivars (Orange Flesh and Goldex), irrigated with water of high salinity in combination with different doses o f K20, two experiments were conducted during 2003 and 2004, in a Red Latosol eutrophic soil at Santa Julia Farm (Latitude 5° 02 0.02' S, Longitude 37° 22' 33.6' V/Gr) in the municipality of Mossoro - RN. In the first experiment, waters of ECw of 0.80 and 3.02 dS m"1 were used in both cultivars fertilized with 273 kg ha"1 of K 20; while in the second trial waters of ECw of 0.52 and 2 41 dS m"1 combined with different doses of K 2 0 (218, 273, 328 383 and 438 kg ha1 ) were used with cultivar Goldex which was found to be more affected by saline water during the Experiment I. The experiments were conducted in a randomized block with four replications and in the Experiment II the treatittents were arranged in split plot scheme. The melon was collected twice at 60 and 64 days after sowing (DAS) in case of cultivar Orange Flesh and at 67 and 70 DAS for the cultivar Goldex. A higher tolerance to salinity of cultivar Orange Flesh was verified in relation to Goldex. Contrary to cultivar Goldex, use of high salinity water (F,Cw = 3.02 dS m" ) in the irrigation of cultivar Orange Flesh showed to be economically viable. In case of cultivar Goldex use of saline water (ECw = 2.41 dS m"') for the cultivation is only viable when higher doses of potassium (varying from 218 to 383 kg ha"' of K 20) are applied. The salinity levels of the irrigation water resulted in higher concentration of salts in the superficial layer of the soil in both experiments when more saline water was used.