Igor Oliveri Soares

Agronomic performance of soybean according to stages of development and levels of defoliation

®according to the stages of reproductive development of the plant at defoliation and the levels of defoliation. A randomized block experimental design was used in a 6 × 3 + 1 factorial arrangement, composed of six reproductive stages at the time of defoliation [R1 (Beginning flowering), R2 (Full flowering), R3 (Beginning pod formation), R4 (Full pod formation), R5 (Beginning seed filling), R6 (Full seed filling -100% pod filling), and three levels of defoliation (33, 66 and 99%), as well as one additional treatment without defoliation, with three replications. The following features were evaluated: Plant height, number of pods per plant, number of grains per pod, harvest index, thousand seed weight, and grain yield. It was observed that all the levels of defoliation had a significant effect on the other variables studied, with the exception of plant height. The phenological stages at the time of defoliation had a significant effect on plant height, number of pods per plant, harvest index, and grain yield. There was a decline in grain yield with levels of defoliation as of 66%, and this decline was more significant with defoliation at the more advanced stages of the crop reproductive cycle.