Silício como atenuante do déficit hídrico em genótipos de feijão-caupi [Vigna unguiculata (L.) Walp.] em condição semiárida

Abstract

The cowpea is of the Fabaceae family (legume) cultivated throughout Brazil, considered as the third largest producer of this crop, highlighting the North and Northeast regions as the largest producers. However, water deficiency is one of the main factors that reduce the maximum productive potential of cowpea, such as loss of cellular turgor, decreased stomatal conductance, reduced transpiration, and, consequently, inhibiting photosynthesis. For this, one of the alternatives may be the use of silicon (Si) in agriculture, which exerts beneficial action for the development of plants, attenuating abiotic and biotic deficits, thus improving the yield of cowpea genotypes. Thus, the objective of the research was to evaluate the effects of foliar silicate application and irrigation depths on the efficiency of water use on the agronomic behavior of cowpea genotypes: BRS Pajeú, BRS Novaera and BRS Pujante, proposing to attenuate the deleterious effects of water restriction in semi-arid conditions. The experiment was distributed in a split-plot arrangement [2 × (2 × 2)], in randomized blocks, with four replications and 30 plants per experimental unit. The main plot was related to irrigation depths (50% and 100% ET0) and subplots by cowpea genotypes (BRS Novaera – G1, BRS Pujante – G2 and BRS Pajeú – G3) with and without application of silicic acid (with 600 mg. L-1 silicon and without (0 mg. L-1). The sprays occurred in the phenological phases in stages V5 (third trifoliate leaf is with the leaflets separated and completely open), stage V9 (third leaf of the secondary branch is completely open), and stage R2 (anthesis of the first flower, usually from the first flower bud). The silicon source used was silicic acid (Si(OH)4). The variables analyzed were growth, phytomass, gas exchange, macronutrienres and sodium, soil chemical attributes and production components, through the root, stem, leaf, green pod, grains by green pod, dry pod and dry grains. The data were submitted to analysis of variance by the F test, the means of the replacement levels of ET0, silicon and cowpea genotypes were compared by Tukey's test, at 5% probability of error. In general, silicon provided attenuation of water deficit with increased growth, grain yield and development in cowpea genotypes; in addition to optimizing the total dry mass intake; the BRS Pajeú expressed larger stem diameter, leaf area, shoot dry mass and total dry mass, in the irrigation depth without water deficit with application and without silicon application; BRS Novaera demonstrated the highest number of dry pods per plant in all types of treatments evaluated (irrigation depths and silicon application), thus presenting the highest grain yield both with silicon application and without the application; the cowpea genotypes BRS Novaera, BRS Pujante and BRS Pajeú are indicated for cultivation in semi-arid regions.