Post-emergence application of herbicides and growth regulators on soybean growth and agronomic performance

Abstract

Plant lodging is among the factors that limit the productive potential of the soybean crop. Growth regulators or even herbicides may be used in pre- and post-emergence of soybean to minimize the chance of lodging. These products can act to reduce plant height or the number of branches. This study aimed to evaluate the growth and agronomic performance of soybean under the post-emergence application of growth regulators and herbicides. Two experiments were conducted in Palotina, Paraná State (PR), Brazil. A randomized complete block design with four replications was used. Treatments consisted of the application mepiquat chloride, trinexapac, cloransulam, lactofen, and control (without application). Crop injury, chlorophyll indices, and variables related to growth and agronomic performance of soybean crop were evaluated. Post-emergence application of lactofen (36 g a.i. ha−1) or cloransulam (33.6 g a.i. ha−1) on soybean (V3–V4) reduced the height of soybean plants, but showed no negative effect on soybean yield. Therefore, these herbicides are alternatives to reduce the lodging of soybean plants. Post-emergence application of mepiquat chloride (100 g a.i. ha−1) was selective to soybean plants, but did not reduce plant growth. Trinexapac application (125 g a.i. ha−1) did not reduce plant growth and had a deleterious potential on soybean yield. Therefore, post-emergence application of trinexapac on soybean is not recommended.