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How dry was the 2021 growing season?

Joe Lauer
In spite of low precipitation, corn grain yields have been good to excellent for most farmers in southern Wisconsin.

This year, southern Wisconsin experienced dry conditions during the growing season. In spite of low precipitation, corn grain yields have been good to excellent for most farmers in the area.

The University of Wisconsin Agriculture Research Station (UW-ARS) at Arlington began collecting weather data in July of 1962. How did the 2021 growing season compare to the previous growing seasons at Arlington for precipitation? 

Growing season (April 1 to October 31) weather data (1963 to 2021) were obtained from the Midwest Region Climatological Center for the UW-ARS at Arlington. A 58-year average was calculated along with the standard deviation of the mean. The standard deviation was multiplied by 1.25 to get the wettest and driest growing seasons over this time period. The accumulated precipitation was compared to the average for each day during the study period. The daily deviations from the average accumulated precipitation are shown in Figure 1.

The wettest growing seasons during this time period were 2019, 2018, 2010, 2008, 2006, 1993, and 1980. The driest growing seasons were  2012, 198819761971 and 1963.

The 2021 growing season ranks as one of the driest on record for the UW-ARS at Arlington. Precipitation patterns can be localized varying dramatically even within a farm.

In spite of being one of the driest seasons on record, grain yield of the UW Corn Hybrid Performance Trial averaged 254 bu/acre.

Record grain yield years usually have the following characteristics:

  1. Earlier than normal planting with adequate spring soil moisture to activate herbicides;
  2. A mild moisture stress ("mini-drought") during early corn development that fosters deep root penetration into the soil profile with soil moisture eventually replenished to normal levels by pollination (1-inch of precipitation per week);
  3. Corn development typically ahead of normal at some point during the growing season;
  4. A fall killing frost at the end of September or during October;
  5. Dry fall harvest conditions.

The 2021 growing season was typical of a record year, except that corn was challenged with a late-May frost event, rainfall of less than 1-inch per week during July to September, and a late incidence of Tar Spot.

The lesson I learned from this season is that corn could get by with less than 1-inch of rain per week during July to September and still yield well. The efficient use of water might be attributed to the European Corn Borer transgenic trait grown in most modern hybrids.

Joe Lauer

Joe Lauer is an agronomy professor at the University of Wisconsin-Madison and UW-Madison Agronomy and UWEX state corn specialist