Desempenho de feijão-caupi sob lâminas de irrigação cultivado sobre palhada no cerrado de Roraima

Abstract

The aim of this study was to evaluate physiological characteristics, yield components, yield and water use efficiency of cowpea cultivars under different irrigation levels. From February to April and from September to November of 2012, two experiments were conducted in no-tillage system in the Cerrado, at the experimental field Água Boa of the Embrapa Roraima. Five sprinkler irrigation levels (30%, 60%, 90%, 120% and 150% of the reference evapotranspiration -ETo), which were daily estimated using the class A tank installed near to the experimental area, were used. The coefficient of the tank (Kt) 0.75 was adopted and three varieties of cowpea (BRS Guariba, BRS Novaera and BRS Pajeú) were evaluated. The experimental design used was the randomized blocks, with the treatments arranged in strips, in a split-plot design with five replicates. The traits plant height, shoot dry weight, leaf area index, yield components, yield and water use efficiency were evaluated. Data were subjected to analysis of variance, the mean of cultivars compared by Tukey test and those relating to the irrigation levels by polynomial regression. The increase of the irrigation levels increased plant height, shoot dry weight and leaf area index. BRS Pajeú presented quadratic effect, where the maximum efficiency for the irrigation levels of 106.84% (317.75 mm ) to 30 g dry mass of shoots and 89.31% (265.62 mm) to 2.74 in leaf area index. There were differences between BRS Guariba, BRS Novaera and BRS Pajeú in response to irrigation. BRS Pajeú showed no influence of the irrigation levels to yield components and grain yield. On the average of the cultivars, the maximum number of pods per plant (12) was obtained with the irrigation level of 81.35% (247.4 mm). The irrigation levels did not affected the number of grains per pod. Weight of hundred grains of BRS Novaera was superior (above 22 g) to the others cultivars. BRS Guariba and BRS Pajeú had means of 19.63 g and 18.61 g, respectively. BRS Guariba and BRS Novaera reached the maximum grain yield (1275.19 kg ha-1 and 1504.98 kg ha-1, respectively) at the irrigation levels of 74.3% and 94.02% (157.27 mm and 199 mm respectively). The maximum water use efficiency was obtained at irrigation level of 30% of ETo (107.3 mm) for the three cultivars.