South America Calling

The wet season in central and northern Brazil usually starts at the end of September. During La Ninas, like we are currently experiencing, that can be delayed by a couple of weeks. But the rain usually continues after it starts. This year has been different so far.

While the first 25 millimeters (about 1 inch) of rain actually fell early in a lot of areas of central Brazil, coming around Sept. 20-23, the rainfall afterward was anything but consistent. For the last two months, fronts moving up from Argentina have been supplying occasional precipitation, but have been wiping the skies dry afterward, resulting in many areas experiencing less than 40% of their normal rainfall.

Models had been rather consistent in the medium range with heavy rain that would fall, but the actual amounts have been far below expectations.

This has resulted in widespread and dangerously low soil moisture for the first soybean crop in central Brazil. Satellite estimates from southern Mato Grosso do Sul and Parana south through Rio Grande do Sul show adequate soil moisture for now. But farther north, the rainfall has not been just below normal, it hasn't been able to improve soil moisture at all. Most soils are rated with insufficient moisture from data as of Nov. 30. When it is not raining, skies are clear and temperatures soar close to 40 degrees Celsius (104 Fahrenheit). Both have been causing stress.

For those that planted soybeans early, producers have been getting just enough rain to get the soybeans by and even inadequate rainfall early in crop development may not cause much yield loss. Reports of replanting and shriveled plants have been sparse. But there has been concern as those early planted varieties are now in their reproductive stages of growth, either blooming or in some cases already setting pods.

Producers there have been sighing with relief this week though, as thunderstorms have been much more numerous and models have finally been proven right. Since Dec. 1, many areas from Mato Grosso to Minas Gerais and points northward have seen rain in the 25- to 50-millimeter range (1- to 2-inch range) with pockets of heavier amounts. Farther south, from Mato Grosso do Sul and Sao Paulo to Parana, the rainfall has not been nearly as consistent but has still been falling.

The forecast is to continue the heavy rainfall over central and northern Brazil during the next week. A system moving up from Argentina is again forecast to produce widespread and heavy rainfall across the south in the Sunday-to-Tuesday timeframe. This time, the forecast may be closer to being right. Rainfall amounts through Dec. 11 are largely in the 50- to 100-millimeter range (about 2- to 4-inch range). Rainfall with that intensity is likely to increase soil moisture dramatically and could cause flooding for some areas where soil moisture is currently more favorable. Far southern areas are not forecast to see quite that much rainfall. From Parana southward, the forecast is calling for more scattered showers and amounts less than 50 mm, though some spots may end up with heavier amounts in there. Dryness may start to become more of a concern across the south unless the forecast improves. Long-range forecasts continue to suggest a drier-than-normal December, especially going south into Argentina. Concerns abound for many areas yet as planting has not even finished across the southern half of the continent.

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

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