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February 6, 2014

Brazilian Farmers Warned not to Apply Descants too Early

As Brazilian farmers adopt early maturing soybeans in order to allow more time for a second crop of cotton or corn, many farmers are routinely apply descants to the maturing soybeans in order to speed up the maturation process. The use of descants can allow a field of soybeans to be harvested at least a week to ten days earlier than normal and even earlier than that during periods of wet weather. Scientists though are warning that applying the descants too early may hurt the potential yields.

After a descant is applied to soybeans, the leaves quickly drop of the plant, the stems dry out, and the field is ready for harvest in 7-10 days. The advantages of using a descant include: speeding up the maturation process which spreads out the harvest so everything is not ready for harvest at the same time, it results in more uniform dryness of the soybeans allowing for a faster harvesting pace, early harvested soybeans generally command a premium in the market and lower freight rates, and most importantly it allows more time for a second crop of cotton or corn.

According to research conducted by the Mato Grosso Foundation, the ideal time to apply a descant is at the R7.3 stage when more than 75% of the leaves have started to turn yellow. In order to accelerate the process though some farmers have applied the descants at R7.1 stage when less than 50% of the leaves have turned yellow or the R7.2 stage when 50-75% have turned yellow. Applying a descant too early before the leaves have started to turn yellow can result in yield losses of up to 12 sacks per hectare or 10 bu/ac.

Farmers also need to pay close attention to the weather forecast before they apply descants. If there is an extended period of wet weather after the field is ready for harvest, the result may be poor quality seed or even yield losses. Every time a mature soybean pod goes through a wet and dry cycle, there is an increased opportunity fungus to invade the pod and the seeds.

Scientists also warn that this practice should only be used for grain production and not seed production. Soybeans grown for seed need to complete the maturation process naturally in order to insure the highest possible germination of the seed.