The number of days available to complete spring fieldwork in Iowa is shrinking significantly — by an average of nearly one full day every four years. Each year USDA collects data on the number of suitable days for fieldwork from local observers in each crop reporting district. The actual number of days available varies considerably year to year, but the trend has been for a shrinking window of opportunity.
Looking at USDA data over the years, William Edwards, Iowa State University Extension economist emeritus, found that the trendline for days suitable for fieldwork from April through mid-June has dropped from 48 days to 35 days since 1964. There were only 26 suitable days available for fieldwork last spring, the fifth fewest amount in the past 55 years. All five of the years with the fewest spring fieldwork days have occurred since 1993, aligning with a trend for increased spring rainfall.
NW Iowa with biggest decline
Some areas of the state have seen sharper downtrends than others. Northwest Iowa has seen the sharpest decline in spring field days, followed closely by north-central Iowa, losing a full day in just over three years, on average. On the other hand, southeast Iowa has shown a significantly slower rate of decline than other areas, losing one field day only every eight years.
The ISU study also shows the number of suitable field days since 1964 for the period June 18 through Sept. 9. Summer weather has been less variable than spring weather. One exceptional year was 1993, with about half the normal number of suitable field days. Many fields were flooded through most of the summer that year.
Looking at fieldwork days each year during the fall harvest season, the two years with the fewest days were 2018 and 2019. The number of good days has been declining in the summer and fall but at a slower rate than in spring. Summer field days have been declining one day every 10 years, while fall days have been declining one day every 15 years.
More on suitable field days is at ISU’s Ag Decision Maker website. Search for Days Suitable for Fieldwork in Iowa, A3-25.
Trend for wetter springs
“The trend is for wetter springs,” says Dennis Todey, director of USDA’s Midwest Climate Hub. “We’re seeing more rainfall, bigger rainfall events and more of it coming in the off-season: spring and fall. It’s a concern from a soil standpoint as farmers are trying to get fields prepared and planted, getting out there on soils that are too wet. That creates compaction issues. We also get soil loss from rainfall on saturated ground, so there’s lots of bad that can happen due to this longer-term spring wetness.”
Farmers should prepare for potential planting delays again this year due to the combination of wet soils and chances for increased rainfall this spring, he adds. “When you have a full tank of subsoil moisture going into spring and above-average rainfall in the spring, there’s a definite risk of planting delays.”