CRESCIMENTO, CONSUMO E EFICIÊNCIA DO USO DA ÁGUA PELA MAMONEIRA SOB ESTRESSE SALINO E NITROGÊNIO

Abstract

Considering the potential of castor beans as an alternative for the production of renewable en- ergy and the lack of information regarding management techniques for its cultivation, this study was conducted to evaluate the effect of different levels of irrigation water salinity (ECw) associated with nitrogen fertilization rates (DN) on growth, water consumption and efficiency of water use by castor bean cv. BRS Energia. The experiment was conducted in lysimeters under field conditions, atCCTA/UFCG, adopting a randomized block designin 5x5factorial scheme with three replications. Treatments consisted of five levels of ECw (0.4, 1.4, 2.4, 3.4 and 4.4 dS m-1) associated with five doses of nitrogen (50, 75, 100;125 and 150 mg kg-1). The increase in water salinity from 0.4 dS m-1 caused linear decrease in the absolute growth rate(TCAap), total leaf area(AF)at 35 days after sowing (DAS), the water consumption and water use efficiency (EUA) for castor bean cv. BRS Energia. Increasing levels of water salinity promoted increase in relative growth rate (TCRap). Nitrogen rate of 114 mg kg-1 increased TCRap and 150 mg kg-1of N promoted greater EUA. Increasing levels of nitrogen at- tenuated at 120 DAS, the effect of electrical conductivity up to salinity level of 2.4 dS m-1 on the leaf area pro- moting higher specific leaf area. There was a significant interaction between ECw and nitrogen levels on elec- trical conductivity and pH of drainage water. Keywords: Ricinus communis L. Quality of water. Mineral nutrition.