Emergence, growth, and flowering of castor beans as a function of the cationic composition of irrigation water Emergência, crescimento e floração da mamoneira em função da composição catiônica da água de irrigação

The use of saline water in agriculture has contributed to the expansion of irrigated areas, especially in arid and semiarid regions, where water deficits occur during various months of the year. In this context, this study aimed to evaluate the emergence, growth, and flowering of the castor bean cultivar “BRS Energia” as a function of the cationic composition of irrigation water, including water containing single and multiple types of cations. The experiment was carried out in a greenhouse in the municipality of Campina Grande-PB, Brazil using drainage lysimeters filled with a sandy loam Ultisol. The experiment was set in a randomized block design, with four replicates each of six water salinity treatments: Control; Na + ; Ca 2+ ; Na + + Ca 2+ ; K + ; and Na + + Ca 2+ + Mg 2 , totaling 24 experimental plots, each consisting of five plants. Plants in the control treatment were subjected to irrigation using water having low electrical conductivity (ECw = 0.6 dS m -1 ), while the plants receiving other treatments were irrigated using 4.5 dS m -1 water containing different ions. Emergence and growth were more affected by the ECw than by the cationic composition of the irrigation water. The order of the cations in the irrigation water, in terms of negative effects, was Na + > Na + + Ca + > Ca 2+ > Na + + Ca 2+ + Mg 2+ > K + . The cationic composition of the irrigation water influenced the time interval for inflorescence development and the opening of flower buds of the castor bean cultivar “BRS Energia”, and the most pronounced effects were observed in plants irrigated with calcic water.