September 12, 2022
The cycle of cooling and warming in the equatorial Pacific isn’t a perfect predictor of weather or crop yields. But the long-lived La Niña cooling phase of the pattern continues to disrupt production – and its impacts may not be over.
The phenomenon is likely one cause for early reports of below normal U.S. corn, soybeans and winter wheat yields in 2022. And even though forecasters predict the El Niño/Southern Oscillation will finally retreat to neutral next spring, an unusual third La Niña winter could disrupt winter wheat production on central and southern Plains fields already suffering from prolonged drought. And hopes for soybean and feed grain yields in South America could already be in the cross hairs of worsening conditions.
As its name suggests, the ENSO is composed of two features. The first is the warming and cooling of ocean waters. For an official El Niño or La Niña designation, unique atmospheric conditions in the Pacific must also be present, highlighting the difference between readings in Tahiti and Darwin, Australia. Both factors must be present for three consecutive months before the designation is made, so forecasts are made for three-month periods.
The current La Niña phase began in July/August/September 2020 and persisted for all but two periods since. The official advisory issued by U.S. forecasters last week said these conditions would not move back to neutral until February/March/April 2023. That would mean three winters in a row of La Niña, something that’s happened only twice since recordkeeping began in 1950 – from 1998-2000 and 1973-1975. While this isn’t enough to be statistically significant – not the result of mere chance – U.S. soybean yields were below normal during both periods, while corn was also poor in the 1970s, though not in the stretch at the end of the last millennium.
U.S. wheat crop at risk
In the U.S., corn and soybean yields are most closely correlated with the summer ENSO cycle, benefiting from El Niño and suffering under La Niña. But even though these connections are statistically significant, they only explain a small portion of the variance in yields from year to year. The same holds true in the Southern Hemisphere, where the ENSO cycle is important, but also far from a slam-dunk.
Still, worrying trends are already present, from the U.S. southern Plains to Argentina’s Pampas.
Forecasters last week said 53% of the U.S. winter wheat crop is affected by drought, including 85% in Nebraska and 86% in Kansas.
La Niña winters are worrisome for wheat on two counts. Temperatures on the southern Plains tend to be warmer than normal, further drying soils that receive below average precipitation. Lack of snow cover could also diminish protection from untimely cold snaps that increase the potential for winterkill.
But even another La Niña winter wouldn’t necessarily doom the crop to a complete bust. With La Niña expected to gradually fade, winter wheat yields might only be cut 3% from what would normally be expected. If growers increase seedings as found by the recent Farm Futures survey, all wheat production could be nearly 200 million bushels better than the stunted 2022 crop.
And some U.S. competitors might even benefit from another La Niña. Wheat yields in Australia can be devasted by El Niño, but tend to be better than normal when La Niña is around.
South American fears
While the size of U.S. corn and soybeans crops are still hotly debated, attention is already turning to South America, where soybean planting can begin soon in Brazil. La Niña during the last quarter of the year is associated with below normal rainfall in Argentina and Brazil, along with warmer than normal temperatures in Argentina. This in turn can affect feed grain yields in both countries. Soybean yields in Argentina can also be cut, though the impact on Brazil appears minimal.
Soil moisture in much of Argentina and northeast Brazil is already below normal after disappointing rainfall over the last three months, an ominous start following disappointing soybean yields for 2021-2022 in both countries, poor 2020-2021 corn production in Brazil and a subpar crop in Argentina harvested earlier this year.
Nonetheless, it’s important to recognize how difficult weather forecasts are – especially months in advance. A case in point is the forecast for an active hurricane season due to La Niña that has so far yet to pan out.
Farmers could eventually get another reminder of those risks, courtesy the soybean market. Preliminary August weather data suggests late season rains may have boosted yield potential back above the 52.2 bushel per acre statistical trend yield, La Niña or not.
And even if USDA reports differently now, it’s estimates can and often do change before they’re finalized in January.
Indeed, betting on weather this winter is a little like trying to pick a Super Bowl winner at the start of the season. Your guess now on the gridiron may be as accurate as these La Niña weather forecasts.
Knorr writes from Chicago, Ill. Email him at [email protected]
The opinions of the author are not necessarily those of Farm Futures or Farm Progress.
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