By Scott Irwin, Department of Agricultural and Consumer Economics at the University of Illinois
There is considerable discussion about the potential impact of the current La Niña episode on South American growing season weather and the resulting effect on crop yields. We define a La Niña episode as one in which the actual three-month running mean temperature falls below the long-run average temperature by at least 1.0 C for at least one month during July through December. There have been 11 La Niña episodes over January 1977 through October 2020. On average, La Niña episodes of this type have occurred once every four years.
The pattern of average corn and soybean yields in years following a strong pre-season La Niña episode provides mixed information for yield expectations. For Brazil:
- The average corn yield in the 10 years was 0.7 bushels below trend. The average soybean yield was 0.8 bushels above trend.