Produtividade e rentabilidade de algodoeiros sob manejos de irrigação e de cobertura do solo no semiárido

Abstract

Cotton is an autogamous plant belonging to the genus Gossypium, species G. hirsutum and the Malvaceae family, where it is cultivated mainly for its fiber. The objective of this research was to evaluate the productivity and financial profitability of three cotton varieties, “BRS 370 RF”, “BRS 286” and “BRS 416”, depending on the factors irrigation depths and soil cover levels, under conditions of the semiarid. The work was carried out on the property called Fazenda Boa Vista, located in the municipality of Pentecoste-CE. The experimental design was in randomized blocks, with a strip system, in sub-subdivided plots, consisting of three primary treatments, cotton varieties, “BRS 370 RF”, “BRS 286” and “BRS 416” associated with five secondary treatments, blades irrigation and five tertiary treatments, soil cover levels, generating 75 treatments with four block replications, 3 x 5 x 5 x 4, totaling 300 experimental units. The variables analyzed were, Lump Productivity, Plume Productivity, Total Productivity, Water Productivity in kg m-3, Water Productivity in R$ m-3, benefit/cost ratio, net present value, internal rate of return and the “payback” period for a ten-year planning horizon. Cotton productivity showed significant variation depending on irrigation depths, decreasing from a depth of 100.01% of ETc, pointing to irrigation management as an extremely important factor for the efficiency of water use and the success of the enterprise. . The adoption of deficit irrigation reduced productivity, however, it increased the efficiency of water use. The water use efficiency in the seed cotton productivity variables, in kg m-3 and in R$ m-3, indicated this as a promising crop for the region, associated with the cultivation techniques adopted in the present work. Mulching with carnauba bagana provided significant results, pointing to its use as an important strategy for conserving soil moisture and reducing evapotranspiration, which directly influence productivity. There was an interaction between the factors, with the cultivar BRS 286 (CV2), and the fourth level of irrigation (L4), equivalent to 100% of ETc, with the fourth level of bagana (NB), 6 cm of coverage with bagana, the which resulted in the best productivity results. According to the results obtained by the financial indicators, cotton production under cultivation conditions on 2.00 ha indicates greater risk to the investor. However, the use of the applied depth, equivalent to 100% of ETc, L4 in the presence or absence of mulch, in the cultivation condition on 10 ha, proved to be the most economically viable condition in terms of sensitivity analyzes of costs and revenues. As a strategy for the growth of cotton exploitation in the cultivation conditions for the Northeast region, it is necessary to encourage access to credit to support agribusiness in the investment and costing modalities, as well as the association of management techniques, respecting legislation and, mainly, soil and water conservation.