Early planting conditions in much of Argentina and southern Brazil have been favorable for the last couple of weeks. But producers in central Brazil, who will double crop soybeans with corn or cotton during the next nine months, await the start of wet season rainfall after months of dryness. They may get their wish next week.

Some areas of Mato Grosso, especially those in the northwest near the Amazon rainforest, have already seen some isolated showers developing and reported amounts have been in the 20- to 50-millimeter (0.8- to 2-inch) range. That effectively is the start of their wet season, but these locations are limited in area. Much of central Brazil (the states of Mato Grosso, Goias, Minas Gerais, Mato Grosso do Sul and Sao Paulo) have yet to see a drop of rain. A front that came through this week looked like it had some promise on last week's forecast but did not produce much of any rainfall.

So, when the forecast is calling for something similar with another front moving north from Argentina for next week, there could be some skepticism. The front is forecast to move through Argentina during the weekend, Sept. 20-21, and then into southern Brazil where rainfall is forecast to be very widespread and heavy. Amounts over 50 mm are in the forecast in various spots of these areas. As the front continues into central Brazil for Sept. 22-23, showers are forecast to become more scattered and not all areas are likely to be hit or see significant rainfall.

One limiting factor could be dew points, as the moisture in the air has been somewhat limited recently. However, that moisture has been increasing this week for those closer to the Amazon as well as across Argentina and southern Brazil. The front moving in could draw more of that moisture together to produce more widespread rainfall than models are predicting.

However, that may not even matter. Recent forecasts have the front effectively stalling from Mato Grosso southeast into Minas Gerais, where showers would continue throughout the week. Producers waiting for that first 50 mm of rainfall to moisten topsoils and begin soybean planting may get their wish.

But it does not come without risk. Not all forecasts are calling for widespread heavy rainfall that the region needs to begin planting, and there may be some concern about dryness returning after the front finally fizzles out later next week.

Should a period of dryness follow after soybeans germinate, that could effectively kill the crop and require replanting. Many producers wait until October when the rains become more consistent to plant anyway; they may choose to do so despite the overall good weather forecast for next week. If the forecast does turn drier for the end of September and into early October, it could mean significant planting delays or replanting, which may produce significant issues with the safrinha (second-season) corn and cotton crops down the line. This still bears watching.

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John Baranick can be reached at john.baranick@dtn.com

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