Combinações de adubação nitrogenada e potássica no cultivo do cajueiro sob estresse salino.

Abstract

The cashew is a crop widely cultivated in the Brazilian Northeast, however the main sources of water used for irrigation in this region have high concentrations of salts, being a limiting factor for agricultural production in this region. To this end, it is necessary to use strategies that mitigate the harmful effects of saline stress on plants. Among the alternatives, mineral fertilization stands out. In this context, the objective was to evaluate the growth, physiological indices and quality of rootstocks of the early dwarf cashew tree 'FAGA 11' grown under different salinity levels of irrigation water and combinations of nitrogen and potassium fertilization. The experiment was conducted under greenhouse conditions, in a randomized block experimental design in a 4 × 3 factorial scheme, referring to four levels of electrical conductivity of the water - CEa (0.3; 1.8; 3. 3 and 4.8 dS m-1), three combinations of nitrogen (N) and potassium (K2O) doses (100:50; 50:100 and 100:100%) with three replications and two plants per plot. The combination of fertilizer with 100:50% N:K of the recommended dose provided a higher relative water content in 'FAGA 11' cashew seedlings irrigated with water with an electrical conductivity of up to 0.3 dS m-1, with no significant difference in in relation to higher salinities. Fertilization using combinations of 100:50% N:K proved to be effective in increasing the stem diameter of early dwarf cashew seedlings. Irrigation with an electrical water conductivity of 4.8 dS m-1 reduced the growth of dwarf-early cashew seedlings, with negative impacts on plant height, number of leaves and leaf area. However, the interaction between the electrical conductivities of irrigation water and the N:K fertilizer combinations did not affect the Dickson Quality Index.