If you get the impression that South American farmers receive rain showers about every time they need them, you pretty much have it pegged right.

Growing season weather patterns in the Southern Hemisphere, especially northern and central Brazil, tend to be frustratingly favorable (in the eyes of U.S. producers). But there are some warts with their weather. And at least one climatologist sees tougher times ahead for our southern competitors.

The last major drought in South America was 1988-89. “But Brazil and Argentina seldom see reduced yield due to drought,” says Iowa State University meteorologist Elywnn Taylor. “It occurs only about one year in 12, compared to one year in six for the U.S. Corn Belt. If they do have a weather problem, it's more likely to be too much water, and that happens about one year in six.”

Crop expansion in Brazil is in the north, which is an almost tropical area, notes Craig Solberg, staff meteorologist with Freese-Notis Weather Service. “There are frequent rains in that area and growing conditions are generally quite good. Even though it's closer to the equator, typically, because of the moisture there is not extreme heat.

“Argentina, however, has a climate similar to the U.S. Corn Belt,” says Solberg. “They can get blocks of high pressure during the growing season and have extended periods of little rainfall. Their chances of dry weather certainly are greater than in northern Brazil.”

Chester Schmitt, ag meteorologist with the National Oceanic and Atmospheric Administration (NOAA), points out through the Brazilian state of Parana and points north, weather is stable. South of there, and into Argentina and Paraguay, the weather is more variable.

“The bottom line,” he says, “is that where the majority of crops are grown in South America, the weather is less variable than in the U.S. But it's not foolproof.”

South America tends to have favorable growing conditions. But private meteorologist-agronomist Larry Acker, of 3 F Forecasts, Polo, IL, says it's not the Garden of Eden.

“In most of Brazil, and particularly as you go north toward the true tropics, the soils are acidic,” he reports. “The pH is 4.8-5 in many locations. That's the area that is being expanded.”

Acker says the combination of high moisture levels in the northern sections of Brazil, along with continuous cropping of soybeans, will likely lead to disease problems.

Ron Heck, a Perry, IA, producer and treasurer of the American Soybean Association, has made several trips to Brazil. He says the country does have problems — several related to weather.

“Their soils are leached and fragile from all the rain they get,” Heck notes. “Those rains also lead to diseases, and fungicides are usually needed.”

Heck says some fields have been in soybeans for up to 10 years straight. “Soybean cyst nematode is creeping in and starting to affect yields.

“Brazilian farmers may rotate to corn or cotton after six or seven years of soybeans, but it's too costly to ship corn for export,” Heck points out. “What's more, cotton is a host crop for nematodes.”

In the longer term, the weather conditions in Brazil could change dramatically, Acker predicts.

“According to our firm's projections, which run though 2008, drier conditions are coming,” he explains. “In fact, the trend has already begun in northeastern Brazil. The city of Recife, which had been getting 40-60" of rain per year, is now in its third year of drought. Recently, it has had only 6-7" of rain annually.”

Acker's projection, based on a proprietary computer model, indicates that the drought area will move south and west into some of the major growing regions of Brazil over the next 20 years.

“This progressive drought will be largely due to the man-made destruction of the rain forests and to the disruption of the Brazilian savanna by row-crop farming,” says Acker. “The savanna, basically a grassland area that includes occasional trees and oases, makes up a large portion of Brazil. Ecologically, it's a fragile area.

“The savanna in Brazil can be likened to the lush savanna that once was in Africa and is now the Sahara Desert,” Acker notes. “That gives you an idea of what could potentially happen in Brazil if the present trend continues.”