With the turn of the calendar to September, the focus in agriculture will be shifting south of the equator, and specifically to Brazil and Argentina, as the two largest competitors to U.S. corn and soybean exports begin their planting season this month. El Nino, which is likely to become the strongest on record by the end of the calendar year, will play an outsized role in the weather patterns for the next several months, primarily resulting in favorable conditions for Argentina and southern Brazil, and unfavorable conditions in central Brazil.

EL NINO TO DRIVE MAJOR WEATHER PATTERNS FOR SOUTH AMERICA

Extremely warm ocean temperatures in the tropical Pacific Ocean, especially just off the coasts of Peru and Ecuador, are indicative of a building El Nino pattern. Global climate models all agree that this year's El Nino, which is expected to peak in November or December, will be the strongest El Nino on record, at least since 1950. Ocean temperatures are forecast to peak between 3.5 to 4.0 degrees Celsius above normal. The current record is 2.6 degrees Celsius above normal during the 2015-2016 Super El Nino.

In South America during strong El Ninos, this event usually brings a much more active southern, polar jet stream while leaving the Amazon much drier and hotter. The jet stream makes for frequent storm systems across Argentina and into southern Brazil, where fronts have a tendency to stall and produce heavy rain. While this could leave parts of Argentina with drier conditions, in general it is a favorable setup. And with frequent rain in southern Brazil, that also tends to be favorable. However, flooding could be an issue at times if these fronts linger for too long. Sandier soils may help some areas to drain more effectively, especially the state of Rio Grande do Sul, which tends to do very well during El Nino. But other areas, especially around the local rivers, could see issues with flooding and severe weather that could threaten crops and infrastructure. Across central Brazil, the wetter pattern in the Atlantic uses up a lot of the moisture, leaving areas near the equator in Brazil noticeably drier. Areas closer to the Amazon, like Mato Grosso, Brazil's largest production state for corn and soybeans, and across northeastern Brazil, are at a higher risk of prolonged dryness. While it will still rain a lot during the wet season there, longer stretches of dry weather may result in significant stress, especially since drier conditions lead to higher temperatures eclipsing 40 degrees C (104 degrees F).

Because this is a likely historic El Nino event, the confidence on such a pattern should be a bit lower. We may find that the extra strength produces some differing effects not just in South America, but also globally. And while no two El Ninos are the same anyway, the above patterns are the ones being forecast not only by the historical record, but by long-range climate models as well.

ARGENTINA AWAITING BETTER PLANTING CONDITIONS, BUT HAS TIME

For much of the winter, Argentina has been cool to cold and rather dry. A shot of heavy rain moved across northern zones in August, which has helped soils from becoming too dry there. But southern zones, and most of the primary growing areas, have seen below-normal rainfall over the last several months. That sets up the planting season as more of a waiting game -- waiting for better temperatures and rainfall to begin planting.

The pattern continues to be an active one in September. Systems continue to push fronts across the country. That is resulting in some precipitation, but not significant amounts except in far northern reaches of the country toward Paraguay and Brazil. Temperatures behind these cold fronts have also been rather cool and are expected to continue that trend at least for the next couple of weeks. That has and continues to result in areas of frosts and freezes across states like La Pampa and Buenos Aires, which may push producers' planting intentions back if these risks continue deeper into the month. Most of these areas do not begin planting until late September or October anyway, but the thoughts of early planting do not appear to be in the cards either.

Luckily for Argentina, the planting windows are generally rather wide open and come in two distinct phases, especially for corn. The first phase begins in September and October. These plants pollinate in November and December while spring and summer rains are still rather frequent. The next phase of planting is in December and January. If there is a dry period in the summer, it is most likely to come in January. So, if corn was planted in November, it would be pollinating in January. Therefore, producers there spread out the risk of having a dry period by planting in both windows, leaving soybean planting later to keep the crop from filling pods in January.

As the crop continues through the summer and into the fall, variable rain and temperature patterns usually favor good growing conditions, but do not have to. The variability could also mean some areas remain too hot and dry during important phases depending on the timing of planting. This usually favors the late-planted crop over the early-planted one, especially if soil conditions are not ideal at the start of the season.

SOUTHERN BRAZIL PLANTING TO GO QUICKLY WHEN RESTRICTIONS LIFT

The heavy rainfall pattern in southern Brazil this winter has allowed for quick increases in soil moisture prior to planting. Much of the region is in good condition and ready to start soybean planting. However, the government restricts soybean planting times in order to better control diseases and fungus. Restrictions lift anywhere from Sept. 1, in portions of the state of Parana, to Oct. 1 in Rio Grande do Sul and Sao Paulo, giving the region potentially several weeks yet before planting can begin. And only small areas are able to go before Sept. 16.

Additional rainfall will help to prime soils before these restrictions are lifted. And the weather pattern during the month of September looks like it will continue to offer multiple chances for slow-moving fronts to bring about some areas of heavy rain.

In all likelihood, dryness concerns will be absent at the start of the season and will not be much of an issue through the middle of 2027. El Nino is likely to continue an active pattern during the entire soybean growing season through filling in January and February, and potentially longer through the safrinha (second season) corn season. While this sounds like a beneficial pattern, and should be on the whole, there are higher risks of severe weather and flooding that could potentially cause issues if they come at inopportune times during the season. Areas around rivers will be at greater risk of overland flooding and transportation issues could arise for transporting grain down to the primary ports as well.

CENTRAL BRAZIL PLANTING CONDITIONS MAY BE VARIABLE TO START, DRYNESS CONCERNS DURING THE HEART OF THE WET SEASON

The largest concerns for South American weather that would affect agriculture will occur across central and northeast Brazil. Some of the most important and widespread farmland exists in the states of Mato Grosso, Mato Grosso do Sul, Goias, Minas Gerais, and Bahia, which account for roughly 60% of all soybeans and 70% of all corn production in Brazil. Big weather problems here would affect world supplies that expanding acreage may not be able to adjust for.

Soybean planting here is restricted as in southern Brazil, with most of the restrictions lifting between Sept. 16 and Oct. 1. Many areas tend not to plant until wet season rainfall begins and becomes rather frequent, ensuring good establishment of early seedlings and rapid growth. Those wet season rains don't typically start until very late September or early October anyway. However, early rainfall that may occur from fronts pushing northward from southern Brazil could give producers a false sense of optimism. That scenario played out just last year, when several fronts brought heavy enough rain in September to get many producers planting early. However, when the true wet season rains were delayed until mid-October, some areas became so hot and dry that replanting was necessary. The same situation may play out again this year as fronts should be frequent across the south and could spread some moisture farther northward as well. Any of these priming showers should generally be a favorable situation this year though, as the wet season during El Nino typically starts on time anyway. It just does not come in with the frequency and intensity that is typical for the region.

During El Nino, the warm waters in the Pacific evaporate incredible amounts of moisture into the atmosphere, producing widespread heavy rain and thunderstorms near the equator, but out over the open ocean. The upward motion from the thunderstorms over the Pacific leads to downward motion to the east over land, resulting in fewer showers and storms over the Amazon rainforest and most of northern Brazil and Central America. Already, this has had a major impact on the water levels in the Panama Canal, where restrictions to barge traffic have already occurred. For central Brazil, areas closer to the Amazon, and Mato Grosso in particular, are more at risk of seeing less-frequent and less-intense rainfall throughout the season. When it does not rain, temperatures become much hotter and often eclipse the 40 C threshold. If a particularly dry stretch occurs at an inopportune time, like during pod fill in December and January, there could be significant impacts on soybean production. Any problems during the heart of the wet season are likely to have spillover effects for the safrinha corn season as the region relies on built-up soil moisture to sustain corn through the fill stage in May and June. If soil moisture reserves are low, it becomes difficult for corn to build much dry matter, which results in lower yields. Such was the case during the last El Nino during the 2023-2024 season, which saw relative drops in yield for both soybeans and corn across Brazil, even though that included some better conditions across the southern end of the country that year.

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

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