Comportamento de cultivares do algodoeiro herbáceo (Gossypium hirsutum L.) sob diferentes percentagens de sódio trocável.

Abstract

The present work, developed from July 1988 to March 1989, in Casa de Vegetação, aimed to identify the most productive cultivars in sodium, as well as their tolerance levels. Eight kilos of material from an eutrophic alluvial soil with a sandy loam texture, from the Perimeter Irrigated of Sumé, PB, was used as substrate. A completely randomized experimental design in a 5x5 factorial arrangement with four replications was used, the factors being represented by the cultivars of the herbaceous cotton CNPA Acala i; Early CNPA 1; CNPA 21-1; CNPA 3H and IAC 2 0, and by the percentages of exchangeable sodium (PST) of 1.4 (control); 14.5; 27.8; 41.4 and 51.0 obtained by adding Na2C02N solution to the soil. At the time of planting, fertilization in the foundation was carried out using 2.4 g of triple super phosphate and 4.8 g of potassium chloride per pot, while in nitrogen fertilization in addition to three foliar applications of urea at 0.5 %, 3.0 grams of ammonium sulfate and 3.2 g of urea were used. The variables were studied: number of seeds germinated, 15 days after planting; opening of the first boll (days) diametrical growth of the stem and plant height at 30, 60, 90 and 110 days after planting; percentage of shedding; average number of boll; average boll weight and seed cotton production. With regard to PST, effects were observed significant at the 0.01 probability level for all variables studied. Regarding cultivars, there were significant effects at the 0.01 level of probability for the variables plant height, number of boll and average weight of boll and 0.05 for the opening of the first boll. The interaction between cultivar and PST was not significant in no variable. The variables number of germinated seeds, opening of the first boll and percentage of shedding, achieved the best results in PST close to zero, however, the other variables behaved better in the PST range between, 7 and 17. Regarding seed cotton production, cultivars behaved similarly, however, the difference found between treatments with PST 1.4 and 51.0 was 79%, that is, the production at first it was 4.7 times more than the last. In general, cultivars were affected by exchangeable sodium from very low levels, however, compromising production damage only occurred in PST greater than 27.3. In the treatment with PST of 51.0, all growth and production variables were severely affected, including the lengthening of the crop cycle.