Salinidade da água de irrigação e frações de lixiviação no cultivo da cana-de-açúcar

Abstract

The sugarcane is a great economic interest culture in Brazil, and Pernambuco much of its production takes place in coastal areas. In these areas the water used for irrigation may have a high content of salts due to the intrusion of sea water, and when brackish water is used to water supply of a culture without an adequate handling, can occur salinization of the soil, reducing the development of plants under the effect on osmotic potential and toxic ions in high concentrations. Therefore, it is necessary knowledge and application management of brackish water use techniques in agriculture, may be excessive salinity controlled by application of leaching fraction and thus ensure a better production yield. Knowing that each culture responds differently to the same salt level in which it is submitted, the aim of the present work was study the growth, yield and concentration of macronutrients and sodium and chloride in the culture of sugarcane irrigated with brackish water and leaching fractions. It adopted a completely randomized design in a 5x2 factorial scheme with four replications, with five levels of irrigation water salinity (0.5, 2.0, 3.5, 5.0 and 6.5 dS m-1) and two leaching fractions (0 and 0,17) corresponding to 100 and 120% of crop evapotranspiration, in which the management of irrigation was performed daily. The biometric variables and production were: number of tillers (NP) and leaves (NF), stalks height (AC), stem diameter (DC), leaf area (AF), stalks productivity (PROD), dry mass of the stalks (MSC), fresh mass of the pointer and leaves (MFPF) and dry mass of the pointer and leaves (MSPF). It was also monitored the electrical conductivity and the Ca, Mg, Na and K leached besides, analyzed macronutrients and the elements sodium and chloride in stalks, pointer and leaves. The salinity of irrigation water affected negatively the growth variables and yield in sugarcane, with the higher results with the use of leaching fraction. The increase in water salinity linearly reduced levels of nutrients N, P, K and Mg in the shoots of sugarcane and raised the levels of Na, Cl and Ca, and these results mitigated with the use of the fraction leaching.