CORDÃO SOBRINHO, F. P.; http://lattes.cnpq.br/5182536868262437; CORDÃO SOBRINHO, Francisco Pereira.
Resumo:
Cotton has a great potential to grow in the semiarid region, due to favorable climatic
conditions. However, some technological steps must be improved such as water management
in plants. This work aimed to evaluate the effect of five irrigation depth on growth, yield and
fiber quality of two cultivars of upland cotton. The experiment was conducted at the
Experimental Station of Embrapa Cotton, in Barbalha, CE, in the period of July to December
2010. Treatments consisted of a factorial combination of two cultivars of upland cotton (BRS
Aroeira, BRS Araripe ) and five irrigation depth (260.93, 418.93, 514.21, 711.81 and 894.68
mm). The experiment was carried out on a split plot experimental design, with ten treatments
and four replicates, totaling 40 experimental units. The amount of water replacement (WR)
for each treatment and irrigation event was calculated according to the reference
evapotranspiration (ET0), determined by the Penman-Monteith method, multiplied by the crop
coefficient (Kc) (WR = ET0 * Kc in mm). At harvest it was measured and evaluated, on 10
plants per plot, the stem diameter, plant height and leaf area. Were harvested and weighed the
two central lines of each plot and collected 20 cotton bolls in the middle third of the plant,
determining production per plot and its respective seed cotton yield per hectare and the fiber
quality. The fiber quality variables analyzed were: length, uniformity, short fibers, strength,
elongation, micronaire, maturity, degree of yellowing and reflectance index. The means for
each treatment were compared by Tukey test at 5% probability for the qualitative factor
(cultivars) and regression analysis for the quantitative factors (water depth), using the
SISVAR statistical program. It was observed that irrigation affected significant the stem
diameter, plant height, leaf area, yield and mean boll weight, while the cultivars affected
significantly leaf area, yield and mean weight of bolls. It was also found interaction between
cultivars and irrigation for the same variables affected by cultivars. With respect to fiber
quality, irrigation significantly increased the length, short fiber index, strength, micronaire,
maturity and reflectance of the fiber. Cultivars influenced significantly the percentage, length
and color of the fiber. The highest productivity and better fiber quality was obtained with the
BRS Araripe cultivar irrigated with 514.21 mm. All fiber quality components analyzed were
well suited to the standards required by the modern textile industry.