Determinação da tensão da água no solo para o manejo da irrigação do sorgo sacarino

Abstract

The culture of sweet sorghum has been considered a great option for the production of ethanol, from the agronomic and industrial points of view. As there is no information on the best soil water tension for the beginning of irrigation of sweet sorghum, we aimed to determine on field the soil water tension adequate for the start of irrigation of four cultivars. Two experiments were conducted in Nova Porteirinha-MG, in a randomized block design, in split split plot design with four replications. Every experiment consisted of six treatments of soil water tension (plots); 20, 40, 60, 80, 100 and 120 kPa for the resumption of irrigation of sweet sorghum, and four cultivars of sorghum (subplots): BRS 508, BRS 509, BRS 511 and CMSXS647. After planting the plots had soil moisture raised to field capacity (10 kPa), when thereafter the treatments were applied. During the application of the treatments, when the soil water tension reached the established tension threshold, the irrigation system of treatment was activated, working the time required to raise the soil water tension to 10 kPa. The amount of response water in each irrigation was obtained with the aid of the soil water retention curve of the experimental area. We evaluated yield of green mass, plant height, broth volume, juice weight, soluble solids (° Brix) and tons of °Brix per hectare (TBH). The different soil water tension, different cultivars, crop year and the interaction between the tensions and the year affected significantly (p0,01 e p0,05) the evaluated variables, according to the F Test. The cultivars responded linearly to the soil water supply. Considering the TBH, the treatment 20 kPa provided the highest amount of ° Brix per hectare. The BRS 511 and CMSXS647 cultivars had the highest values tons of ºBrix per hectare in 2013 and 2014.