CASTOR BEAN PRODUCTION AND CHEMICAL ATTRIBUTES OF SOIL IRRIGATED WITH WATER WITH VARIOUS CATIONIC COMPOSITIONS

Abstract

This study aimed to evaluate the production of castor beans, cv. ‘BRS Energia’, in terms of soil chemical composition as a function of the cationic nature, and salinity levels, of the irrigation water. The experiment was carried out using lysimeters in a controlled environment at the Center of Technology and Natural Resources of the Federal University of Campina Grande, from November 2013 to February 2014. The treatments consisted of six types of salinity (S₁ - Control; S₂ - Na⁺; S₃ - Ca²⁺; S₄ - Na⁺ + Ca²⁺; S₅ - K⁺, and S₆ - Na⁺ + Ca²⁺ + Mg²⁺), distributed in randomized blocks with four replicates; each plot  consisted of five plants for evaluation, totaling 120 experimental plots. Plants in the control treatment (S₁) were irrigated with water with an electrical conductivity (ECw) of 0.6 dS m^-1, and the other treatments (S₂; S₃; S₄; S₅ and S₆) with ECw of 4.5 dS m^-1, but with (a) different cation(s). Water salinity of 4.5 dS m^-1 hampers castor bean production, regardless of the cationic nature of the water; castor bean ‘BRS Energia’ was more sensitive to salinity caused by the presence of potassium salts in the irrigation water; the mass of seeds in the primary raceme is the most sensitive variable to salinity and the cationic nature of the irrigation water; the adopted leaching fraction (0.10) was not sufficient to avoid salt accumulation in the soil; irrigation with low ECw promoted the lowest value of exchangeable sodium percentage.