LAUSR

It was proposed, in the present study, to evaluate the gas exchange and the growth of the castor bean cv. BRS Energia due to the isolated or mixed cationic nature of irrigation water. The study was conducted in drainage lysimeters under greenhouse conditions, using an Eutrophic Greyish Argissolo with a sandy-loam texture in the municipality of Campina Grande, Brazil. A randomized block design was used with six cationic composition of irrigation water (S1-control, S2-Na+, S3-Ca2+, S4-Na++Ca2+, S5-K+ and S6-Na++Ca2++Mg2+ with four replicates, each composed of five plants. The plants under the control treatment were submitted to irrigation with low salinity water (ECw = 0.6 dS m-1) and the remaining treatments were irrigated with ECw of 4.5 dS m-1 prepared with salts of different cations in chloride form. The gas exchanges and the growth of the castor bean cv. BRS Energy were determined at 100 days after sowing. The gas exchanges and the growth of the castor cv. BRS Energy were more sensitive to the variation in the electrical conductivity of the water compared to the cationic nature of the water, being the least deleterious effect observed in the plants irrigated with potassic water. The plants irrigated with water of potassium composition obtained the highest values for stomatal conductance, transpiration and rate of assimilation of CO2; at 100 days after sowing; the castor bean cv. BRS Energia showed sensitivity to the presence of sodium and calcium salts in irrigation water.