Physiology, growth and yield of castor bean under salt stress and nitrogen doses in phenophases
Soares de Lima,Geovani
Almeida dos Anjos Soares,Lauriane
Oliveira da Silva,Alexsandro
High population growth during the last decades and reduced water resources, both in quantity and quality, have made necessary the use of saline water in agricultural activities. This study was conducted to evaluate the influence of irrigation with water of varying salinity in different phenological phases associated with nitrogen fertilization on the physiology, growth and yield of castor bean cv. BRS Energia. Research was carried out in lysimeters under field conditions in Pombal-PB, Brazil, from September 2011 to January 2012. A completely randomized block design arranged in a 5x2x2 factorial design was adopted, with three replications, testing five levels of electrical conductivity of irrigation water (ECw = 0.3, 1.2, 2.1, 3.0 and 3.9 dS m-1), two strategies of management of water salinity: 1) irrigation with low salinity water during the vegetative stage and application of different salinity levels in the reproductive phase and 2) irrigation with different ECw levels throughout the crop cycle, and two nitrogen doses (100 and 160 mg N kg-1 soil). Leaf (DML) and stem (DMS) dry matter and the number of fruits (NFruPC) and seeds (NSeePC) of the primary cluster were evaluated. Irrigation with ECw exceeding 0.3 dS m-1 affected DML and DMS negatively. The greatest accumulation of dry matter was observed in plants which were not irrigated with saline water in the initial development phase. Irrigation with saline water caused changes in gas exchange of the castor bean plant, with varying effects according to the management strategy adopted. The nitrogen dose of 160 mg N kg-1 soil increased DMS. Different ECw levels negatively affected production, regardless of the development stage. No significant interaction effect was observed among the factors studied and the variables evaluated.