Qualidade de grãos de soja dessecada em função da época de colheita

Abstract

Climatic conditions at the time of harvesting of soybeans may influence the final quality of the product, since diferente values of relative air humidity, temperature and precitation can favor infestation by pathogens, and loss of grain quality that follows for storage and marketing. It is common in the northern region of Mato Grosso that there are delas in the harvesting of soybeans due to excessive precipitation, which makes it difficult to manage the mechanized harvesting operation. Thus, the objective of this study was to determine the physiological, physical and fungal quality of soybean seeds from the transgenic cultivar TMG 132 RR, as a function of the delay in harvest, as well as to compare with the unseated soybean harvested at the recommended time. Five harvest stages were evaluated, the first one being performed on the date considered ideal, and the others with 5 (second stage), 10 (third stage), 15 (fourth stage) and 20 days of delay (fifth stage). Grain quality was determined by physical properties: apparent specific mass, actual specific mass, mass of a thousand grains, and grain size and shape; physiological properties: initial germination potential and after accelerated aging, and detection of associated fungi. The physical and physiological quality of unseeded soybeans, harvested at na ideal time, was very similar to that of the first harvesting stage of chemically desiccated soybean. A significant difference was found for all the physical and physiological properties analyzed as a function of the delay in harvest, and were more expressive in the physiological quality. Even with high initial values, the physiological quality of the grains fell sharply after five days of storage in the field. In relation to the incidence of pathogens, due to the delay in harvesting, a significant time effect was observed for fungal genera: Cercospora, Fusarium, Macrophomina, Rizophus and Aspergillus. In general, for all fungal genera found, na increase in incidence was observed due to the permanence of the grains in the field beyond what is necessary to perform the mechanized harvest.