Abstract
ABSTRACT The use of brackish water to cultivate lettuce can cause nutritional imbalances, impairing production. In this context, the objective of the present study was to evaluate the effect of salinity on the accumulation of dry matter of the aerial part and macronutrients K, Ca and Mg and their relations with Na in lettuce cultivars grown in a low-cost hydroponic system. The experiment was conducted in a randomized block design, in a 6 × 2 factorial scheme, with four replicates. The treatments consisted of six electrical conductivities of the nutrient solution (1.5, 2.5, 3.5, 4.5, 5.5 and 6.5 dS m-1) and two lettuce cultivars, Betty [iceberg] and Mimosa [green-leaf]. Regardless of the evaluated cultivar, the increase in the electrical conductivity of the nutrient solution reduced the accumulation of dry matter in the aerial part. In both cultivars, the increase in the electrical conductivity of the nutrient solution reduced the accumulations of K and Mg and increased Na/K, Na/Ca and Na/Mg ratios. The green-leaf cv. Mimosa showed Ca and Mg accumulations higher than that in the iceberg cv. Betty, regardless of electrical conductivity. The increase in electrical conductivity reduced the accumulation of K, in both cultivars evaluated. The decreasing order in the accumulation of macronutrients and sodium in both cultivars was: K > Na > Ca > Mg.
Highlights
The Brazilian semiarid region is plagued by water scarcity and irregular distribution of meteorological factors, which harms agricultural production (Souza et al, 2015)
The objective of the present study was to evaluate the effect of salinity on the accumulation of dry matter in the aerial part and macronutrients K, Ca and Mg and their relations with Na in lettuce cultivars grown in a low-cost hydroponic system
The individual effects of nutrient solution electrical conductivity on the accumulations of dry matter of the aerial part (DMAP), Na, K, Mg and Ca can be observed in Figures 1A, B, C, D and E, respectively
Summary
The Brazilian semiarid region is plagued by water scarcity and irregular distribution of meteorological factors, which harms agricultural production (Souza et al, 2015). Many farmers use brackish waters from natural water reservoirs in the region. As an alternative to minimize the effects of salinity on plants and to financially benefit the rural producer, low-cost hydroponic systems have emerged (Santos Júnior et al, 2013). The increase in electrical conductivity through the use of brackish water can restrict the growth of the photosynthetically active area of the plant, minimizing carbon fixation and biomass production (Negrão et al, 2016), causing direct consequences on the absorption and accumulation of nutrients by plants. Compared to conventional cultivation, an insignificance of the matric potential reduces the difficulty of water absorption by plants (Soares et al, 2007)
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