Leaf Gas Exchange and Nutrients Accumulation in Cowpea Plants Under Different Management Strategies With Brackish Water

Abstract

Many studies have shown that the use of strategies for the management of saline water in irrigation reduces impacts on the soil and crops. We aimed to evaluate the effect of management strategies of irrigation with brackish water on leaf gas exchange and mineral concentrations of cowpea (Vigna unguiculata L.Walp.). The experiment was conducted in randomized blocks with thirteen treatments and five replications. The treatments consisted of: T1 (control), T2, T3 and T4 using water of 0.5 (A1), 2.2 (A2), 3.6 (A3) and 5.0 (A4) dS m -1 , respectively, during the entire crop cycle; T5, T6 and T7, use of A2, A3 and A4 water, respectively, only in the flowering and fructification stage of the crop cycle; using different water in a cyclic way, six irrigations with A1 followed by six irrigations with A2 (T8), A3 (T9) and A4, (T10), respectively; T11, T12 and T13, using water A2, A3 and A4, respectively, starting at 11 days after planting (DAP) and continuing until the end of the crop cycle. Continuous application of the high salinity water (above 3.6 dS m -1 ) over the whole cycle of cowpea inhibits leaf gas exchange, being stomatal conductance the most sensitive variable. The alternate use of brackish water or only in the salt tolerant growth stage reduces the accumulation of potentially toxic ions (especially chloride) and maintains the similar values of leaf gas exchange and total essential nutrients ( K, Ca and Mg) extracted by plants, in relation to plants irrigated with canal water (low salinity).