Determining the level of burndown in soybean genotype with indeterminate growth habit in Mato Grosso

Abstract

For cultivars with indeterminate habit, there are no reports of the most appropriate period to conducted burndown in pre-harvest. The study aimed to evaluate the influence of burndown on three different times over physiological and sanitary quality of seeds and agronomic characteristics of SYN-9074 RR cultivar with indeterminate habit, in three areas simultaneously. It was used a randomized complete block design with four replications, and joint analysis were conducted for the three distinct areas. Treatments refer to the application period of diquat (0.3 kg ha^-1), or better, in soybean plants at maturation stages R6.5 (fully formed seeds, pods 50% yellow and 50% green), R7 (pods 70% yellow, with a fully mature pod on the main stem) and R7.5 (90% yellow pods) and a check without herbicide. Germination test, dry mass of dossel and little root part, shoot length and little root, sanitary condition and mass of 1000 seeds and yield were evaluated. The period more adequate to accomplish burndown in pre harvest of SYN-9074 RR cultivar with indeterminate habit was with plants showing 90% of yellow pods, or maturation period R7.5, that provided higher yield and lower incidence índex of Phoma sp., Colletotrichum dematium var. truncata and Fusarium sp. fungi.