Comportamento de cultivares de algodoeiro herbáceo em diferentes lâminas de irrigação.

Abstract

The study aimed to evaluate the effect o f irrigation leveis on the growth, development, yield, water use effíciency (WUE) and the yield response to irrigation (Ky) o f BRS 286, BRS Aroeira and Araripe of upland cotton cultivars. The experiment was conducted at the experimental field of Embrapa Cotton, in the municipality of Barbalha, CE, during the period July to December 2010. Treatments consisted of a factorial combination (3 x 5) of three cultivars of upland cotton (BRS 286; BRS Aroeira and BRS Araripe), submitted to five irrigation, totalizing 15 treatments, installed in a randomized block design with four replications, totalizing 60 sub-plots arranged in bands. The irrigation water applied in each treatment throughout the experiment, were 260,93; 418,93; 514,21; 711,81 and 894,68 mm. At harvest, was measured in 10 plants/plot, the diameter of the stem, the plant height and leaf area. Also were harvested and weighed the two central lines (useful area) of each subplot, determining yield per subplot and the corresponding yield of seeds per acre. Water use effíciency (WUE) was detennined, for each levei of irrigation through the relationship between the yield of upland cotton (kg ha" ) and irrigation water depth (mm) per subplot during the crop cycle. To evaluate the crop response to irrigation, it was used a dimensionless parameter, that relates the relative reduction in yield with the relative reduction in irrigation water. The average results were submitted to analysis of variance and regression (irrigation), and the averages for the genotypes were compared by Tukey test at 5% probability using the statistical program SISVAR. It was concluded that the irrigation had a significant effect on growth, yield and water use effíciency (WUE) in the BRS 286, BRS Aroeira and BRS Araripe. The variety more resistant to water deficit was BRS Aroeira, followed by BRS 286 and BRS Araripe.