Efficacy of Adjuvants Photoprotectors for Herbicides in Sugarcane

Abstract

Sugarcane is one of the main agricultural crops in the country and is the main raw material used by the sugar and alcohol industry. With the current sugarcane cultivation model, where burning for the harvest is no longer possible, the remaining straw from the mechanical harvest remains in the field. The straw on the ground forms a physical barrier, which reduces the incidence of light and helps to inhibit the growth of some weeds, selecting others adapted to this condition. Among the different weed managements, the application of pre-emergent herbicides is quite usual, but under these conditions the herbicide will be intercepted by straw, which is transported to the soil by leaching in the rainy season or by irrigation. When herbicides are applied during the dry season, they are exposed on the straw surface, subjected to solar radiation and can reach high temperatures. In this environment, herbicides that have photosensitivity characteristics can undergo transformations in their molecules and present photodegradation, not reaching their full effectiveness in controlling weeds. Within this context, this research aimed to study the photosensitivity of the herbicides amicarbazone, metribuzin and sulfentrazone, and evaluating two adjuvants, a concentrated suspension and an emulsifiable concentrate, which allows to protect its molecules from photodegradation. For this an experiment was conducted to simulate the real conditions found in field applications, the samples were subjected to radiation solar for 0, 15, 30, 45 and 60 days. The results were evaluated through the photostability of the herbicides without and with the use of adjuvants. The results found for amicarbazone and sulfentrazone showed that the ideal adjuvant for these molecules was emulsifiable concentrate (EC) formulation and for metribuzin none of the adjuvants were effective, requiring the development of a specific adjuvant for this herbicide.