Salinity management strategies and potassium fertilization in watermelon (Citrullus lanatus) cultivation

Abstract

This study aimed to evaluate the gas exchanges and growth of ‘Sugar Baby’ watermelon under different strategies of irrigation with saline water and potassium fertilization, in an experiment conducted in a protected environment. The experiment was conducted in randomized blocks, in 8 x 3 factorial arrangement, corresponding to eight water salinity management strategies applied at the phenological stages of the crop (NS = no stress along the cycle; VE = salt stress during vegetative stage; VE/FL = salt stress during vegetative and flowering stages; FL = salt stress during flowering stage; FL/FR = salt stress during flowering and fruiting stages; FR = salt stress during fruiting stage; FR/MAT = salt stress during fruiting and maturation stages; MAT = salt stress during fruit maturation stage) and three potassium doses – KD (corresponding to 50, 100 and 150% of the recommendation), with three replicates. Two levels of water salinity were used, high and low values of electrical conductivity (ECw = 0.8 and 4.0 dS m-1). Watermelon growth and gas exchanges, especially transpiration, stomatal conductance, CO2 assimilation rate, instantaneous carboxylation efficiency, and absolute and relative growth rates of stem diameter were compromised by water salinity at the stages of flowering, fruiting and maturation. The potassium dose with 50% of K2O recommendation can be used in the cultivation of watermelon, without negatively affecting gas exchange and growth.