Effect of N fertilization on NPK content in castor bean under saline stress

The high concentrations of salts in water, especially in semiarid regions, increase salt concentration in the soil and plant with the consequent decrease in NPK contents. Current study evaluates the influence of irrigation with water of different salinities, associated to nitrogen (N) fertilization, on NPK contents in castor bean cv. BRS Energia. An experiment was conducted for four months, in lysimeters under the  field condition, in the municipality of Pombal, Paraiba - Brazil, using an  Eutrophic Entisol of sandy loam texture ina randomized 5 × 4 factorial block design with three replications. Five levels of electrical conductivity of irrigation water (ECw=0.3, 1.2, 2.1, 3.0 and 3.9 dS m-1) and four doses of N (70, 100, 130 and 160 mg kg-1) were tested. The highest contents of potassium (K) in roots and leaves were obtained respectively with ECw of 0.3 and 2.2 dS m-1. The N content in leaves was not influenced by factors under analysis. Increase in N dose decreased the plant contents of phosphorus (P) and K.   Key words: Ricinus communis L., electrical conductivity, regressions.