Anticipating the desiccation of soybean crops serves various purposes for producers, including plant homogenization, avoiding rainy periods during harvest, and advancing the sowing of the second harvest. However, research by Embrapa in Mato Grosso revealed that operating outside the recommended period results in a reduction in grain mass and oil content.
Conducted at the experimental field of Embrapa Agrossilvopastoril in Sinop (MT), the study found that desiccation at the early grain formation and filling stage (phenological stage R5.5) led to a significant decrease in the thousand grain mass, ranging from 26% to 19% lower compared to desiccation at the beginning of maturation (R7.1 and R7.3) in two evaluated cultivars.
Extrapolating these findings to a crop with an average productivity of 60 bags per hectare, the difference represents a production reduction between 15 and 11 bags per hectare. Mass losses also occur with desiccation after the R7 stage or harvesting without desiccation at R9, resulting in a 4% to 6% reduction, equivalent to two to three bags less per hectare in a scenario of average productivity.
The research revealed a harvest situation in R9 with a statistically equal mass of one thousand grains compared to the desiccated crop in R7.
Furthermore, the anticipation of desiccation was linked to a reduction in oil content, indicating that oil synthesis appears to be the last constituent in soybeans. Desiccation in the early stages interrupted the photosynthetic process, leading to lower oil content.
The study showed that the sample desiccated at R5.5 had lower oil contents (21.86% and 22.24%) in two cultivars analyzed. At the R7 stages, oil content ranged between 25.67% and 24.26% in the conventional cultivar and between 23.62% and 23.94% in the transgenic cultivar.
The research also evaluated damage to harvested grains at different desiccation points, revealing a lower presence of green grains as maturation stages progressed. While burned or moldy grains were low, the number of broken pieces increased non-linearly with drying time, suggesting potential discounts at the time of delivery.
Additionally, the electrical conductivity of the exudate solution was analyzed to assess grain quality, with desiccated soybeans between R6 and R7.3 demonstrating the best performances in this test.
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