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January 8, 2015

Brazilian Scientists feel Safrinha Soybean Production Unstainable

As the early soybean harvest begins in Brazil, many farmers will quickly plant a second grain crop immediately after the soybeans are harvested in order to take advantage of the long growing season. The vast majority of the second crop will be corn, but in a few cases, farmers may actually plant a second crop of soybeans in the same field where they just harvested their first crop of soybeans. This practice of planting two crops of soybeans back-to-back in the same field, which is called safrinha production, has been criticized by Brazilian scientists as an unstainable practice.

Researchers from Embrapa have demonstrated repeatedly that growing safrinha soybeans can lead to long term problems for normal soybean production. Planting safrinha soybeans can result in a proliferation of diseases such as soybean rust as well as an increase in soil pests such as cyst nematodes and a wide range of other insect pests.

As far as soybean rust is concerned, the time interval between when the safrinha soybeans are harvested (May or June) and the time when the next soybean crop is planted (September) is very short allowing rust spores to remain viable and infect the next crop.

Safrinha soybean production also accelerates the development of resistant diseases, insects, and weeds. Scientists are advising Brazilian farmers not to use the same fungicide more than twice in a row when trying to control soybean rust. They emphasize that a rotation of fungicides with different modes of action is the best way to slow down the development of rust resistant to fungicides. Unfortunately, planting two crops of soybeans back-to-back makes that process more difficult.

The same can be said for weeds and insects. Roundup resistant weeds are becoming a problem in Brazil and the situation gets worse when two Roundup Ready soybean crops are planted during the same growing season.

Safrinha soybean acreage is very small compared to the regular crop. The two states in Brazil with the largest safrinha soybean acreage are Mato Grosso and Parana. Safrinha soybean acreage in each of those states is probably slightly more than 100,000 hectares although accurate estimates are not easily available.

The state of Mato Grosso has taken steps to restrict or completely eliminate safrinha soybean production in the state although the final rules are still being formulated. Farmers in Mato Grosso want to retain the ability to plant a second crop of soybeans as a means of producing seed for the following growing season. In the state of Parana, no such restrictions have been put in place, at least not yet.