Crescimento e produção de dois genótipos de cana-de-açúcar com suplementação de regas com águas salinizadas.

Abstract

Increasing the cultivation of sugarcane in the Brazilian semi-arid areas, usually under irrigation, there is the risk of land salinization, due to the peculiarities of climate and soil of the region, requiring constantly new researches in order to identify genotypes tolerant to salt stress. With this purpose this work was carried out, aiming to evaluate the tolerance of two sugarcane cultivars to salt stress under irrigation in dry periods, using salinized waters. The study was conducted in open drainage lysimeters (4 sugarcane clumps per lysimeter), from December/2011 to Novembro/2012, in UFCG Campus in Campina Grande. The genotypes 'SP 813250' and 'RB 92579' were utilized, combined with five levels of electrical conductivity of irrigation water (0.6, 1.6, 2.6, 3.6 and 4.6 dS m"1), in randomized block design. Salinity levels were obtained with addition of NaCI, CaCI2 and MgCI2 to the water supply system of the city, in the ratio 7:2:1, respectively. The experiment consisted of two phases, being the plants irrigated with water without salt addition, in the first one with duration of 90 days. In the second phase, the plants received irrigations with saline water, after that time, at levels corresponding to the treatments, when the rains did not meet their water requirements. Evaluations were made on sugarcane clumps (obtaining the average of each variable), being obtained the data of growth variables (height and stalk diameter, number of leaves, leaf area, number of tillers), physiological variables (stomatal conductance, transpiration, internal carbon, photosynthesis and fluorescence parameters) and stalk yield. The harvest took place at 318 days after planting, being identified that the variable of tillering is the less suitable for studies assessing the sensitivity to salt stress in sugar cane. The lowest tillering of 'RB92579' was offset by greater height and diameter stalk of this genotype. It was noticed a decreasing of the physiological activity, close to harvest, in both cultivars, with the exception of the internal concentration of carbon that has accumulated in the leaves. The fluorescence parameters were not affected by salinity. The cv. RB 92579 is more tolerant to salinity than 'SP813250', producing 10.54% more at the highest level of salinity.