Desempenho agronômico do sorgo sacarino submetido a regulador de crescimento e qualidade fisiológica das sementes

Abstract

Saccharin sorghum crop has been gaining ground in the Brazilian biofuels market, due to the growing demand for renewable energy. In addition, it is a good alternative to compensate for the off-season of sugarcane (main ethanol raw material in Brazil), it can also use the same infrastructure as sugar cane plants. However, the crop still has some limitations on its production, such as high lodging rates due to its large size. In view of this, the present work aimed to evaluate the agronomic performance of two cultivars of saccharin sorghum submitted to trinexapac-ethyl growth reducer applications at different doses and application numbers. Also, the objective was to verify the physiological quality and viability of the use of seeds produced by sorghum plants that received the applications of the growth regulator. For this, two experiments were conducted, one in the field at the Federal Institute of Education, Science and Technology of Rio Grande do Sul, Ibirubá campus, in the agricultural years 2016/17 and 2017/18, conducted in a randomized block design, with four repetitions per treatment, involving a trifactorial model (2 x 6 x 2) with two cultivars of sorghum (BRS 506 and Fepagro 19), six doses of growth reducer, commercial product (0; 150; 300; 450, 600 and 750 mL.ha-1) and different application numbers (one V5 stage application - 5 expanded sheets, and two applications, one in V5 and one in V8 - 8 expanded sheets) totaling 24 treatments. Plant height, lodging percentage, leaf area index, relative leaf chlorophyll content, plant biomass, leaf and stem dry mass and Brix were determined. The application of trinexapaque-ethyl reduced the height and lodging of saccharin sorghum plants without affecting the green matter yield. The second experiment was conducted at the Didactic and Seed Research Laboratory of the Federal University of Santa Maria (UFSM) in 2017, using seeds from cultivar BRS 506 from the field experiment (2016/17 harvest), conducted in a completely randomized design, with eight replications per treatment, involving a factorial model (4 x 2) with four doses of growth reducer, commercial product (0; 150; 450 and 750 mL.ha-1) and two application times (stage V5, and V5 + V8) totaling eight treatments. One thousand seed mass tests, first germination test count, total germination, sand emergence, seedling length and dry mass, electrical conductivity and accelerated aging were applied. There was a decrease in the physiological quality of saccharin sorghum seeds from plants that received trinexapc-ethyl, mainly with the increase of the number of applications.