South America Calling

More Rain Needed in South America

John Baranick
By  John Baranick , DTN Meteorologist
A front will bring some rainfall to portions of southern Brazil through Aug. 29 while another could bring some rain to Argentina next week. The region will need more rainfall as producers plan for spring planting. (DTN graphic)

A front moved from northern Argentina into southern Brazil this past weekend. It became active this week and rainfall amounts have generally been quite good. Far northeastern Argentina and the state of Rio Grande do Sul in Brazil have seen a general 25 to 100 millimeters (1 to 4 inches). With much of the winter wheat crop getting toward or into reproduction, the rainfall could not have come at a better time as it has been markedly dry during the winter.

That front is making its way up into Parana, Mato Grosso do Sul, and Sao Paulo where it will stall through the weekend with additional showers. This is more likely to be on the order 25 to 75 mm (1 to 3 inches) though there could be some pockets of heavier rainfall. This region has winter wheat that is farther along in development with more of the crop going through reproduction. Again, this is good timing to get meaningful rainfall for the region.

Both areas mentioned should see soil moisture increases as well prior to spring planting. That bodes well for full-season corn, which may be planted at any time now. But producers need to wait into the middle of September to be able to start planting soybeans so more moisture will be needed in this area.

Farther north in Brazil, the front should not make much headway. It is anticipated to stall to the south of the higher-producing regions that have been in drought since the end of March. Brazil has a distinct wet-dry season dynamic due to their proximity to the equator. The wet season shut off abruptly early last season.

Many would blame this on La Nina, as La Nina years have a tendency to shorten the length of the wet season. For the 2020-21 growing season, that was an understatement. The start to the season was delayed by three to four weeks before rains came into the area. At first, the rains were lighter and spottier than normal. They picked up once the calendar turned over to 2021, but then shut down more than a month early, leaving the region in the worst drought in almost 100 years.

The forecast is for another La Nina to peak this spring to early summer and start to wane by fall, much like the La Nina of 2020-21. This coming La Nina is not forecast to be as strong as last year's, but the same risks will show up this year as well. A delayed and shortened wet season puts second crop (safrinha) corn that is planted after soybeans are harvested, in a precarious situation. Frosts in the winter are also more likely. Winter 2021 saw three rounds of frosts occur over much of Brazil, damaging corn that was still in reproductive to early fill stages. Could the coming year show the same? It is doubtful to be as bad, but the risks for all three -- a delayed start to the wet season, an early start to the dry season, and a greater potential for frosts in the winter -- are on the table.

Farther south in Argentina, soil moisture is below normal. Currently, it is enough for wheat during the early stages of growth. Lower temperatures and frosts this week have slowed growth, but temperatures are on a warming trend through the weekend into next week. The region is going to need more rainfall and soon as winter wheat development accelerates over the coming weeks.

A system is set up to move through the country in the middle of next week, around Aug. 31 to Sept. 1. Rainfall from this system will be a good start, but the region will need more. Luckily for producers, it appears that showers could stick around the region through Sept. 4, benefiting soil moisture further while temperatures fall below normal again.

There are two periods of corn planting that are done in Argentina. The early period is from September to October, while the later period is in November and December. This is done to reduce the risk of having a stretch of dry weather during pollination. While the current forecast for showers will be beneficial for those that are trying to get an early start to planting, there is some time yet for rainfall to increase this spring to begin planting. La Nina does not typically have a strong trend toward adverse or favorable conditions in Argentina, but that means that the season could go either way. A negative season happened in the 2020-21 season where drier conditions were noted, especially early in the season. It is possible a more positive season will happen this year.

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

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