TEORES FOLIARES DOS MACRONUTRIENTES CATIÔNICOS E SUAS RELAÇÕES COM O SÓDIO EM PLANTAS DE MILHO SOB ESTRESSE SALINO

Abstract

The saline stress is one of the most detrimental factors restraining the growth and the yield of the crops, as inducing the morpho- logic, structural and metabolic modifications, in the agronomic plants. The effects of soil salinity on the nutritional contents of cationic macronutrients and their relationships with sodium were studied, by using a maize variety cropped in drainage lysimeters under greenhouse conditions. The experiment was set up in an entirely randomized experimental design with seven treatments: one irrigated with fresh water and without leaching; and six ones irrigated with saline water of 1.2 dS m-1 and leaching fractions of 40, 30, 20, 15, 10 and 5% of the applied irrigation depth, and three replicates. The effects of the soil salinity on the mineral nutrition of the maize crop were evaluated, by determining the leaf contents of the cationic macronutrients and their relationships with sodium at 30, 60, 90 and 120 days after planting. The increased soil salinity promoted by irrigation with saline water also increased the sodium contents, the relationships Na+/Ca2+, Na+/Mg2+, Na+/K+, but reduced the contents of calcium, magnesium and potassium, therefore characterizing the unbalance and the nutritional stress consequent to the progressive saline stress.