Agriculture & Water Management

The 2022 Ag Census data was released on February 13, 2024. One census question asked, “During 2022, considering the total acres on this operation, how many acres were drained by tile?” This is the same question that was asked in 2017.

Importance of subsurface tile drainage in the Midwest

Subsurface tile drainage is concentrated in the corn belt (Figure 1). It accounts for a considerable portion of the cropland harvested in the Midwest, especially in states that are dominated by rain-fed agriculture and have poorly drained soils that require drainage (Figure 2). These states have some of the world’s most fertile soils that require subsurface drainage for crop production. Without drainage, crop production would not be able to meet the growing food demand because of poor crop yield due to excess water. Read more about the Pros and Cons of drainage.

If the field is not dried out before spring field operation, it could delay planting, or even prevent planting altogether like in 2019. On the other hand, if field operations are performed on wet soil, it could cause soil compaction, which in turn reduces infiltration, increases surface runoff, causes drainage underperformance and harms the crop from wet stress. Therefore, increased crop yield, reduced year-to-year yield variability, timely field operations and trafficability are some of the main reasons why subsurface drainage is expected to increase.

Variation in acreage of tile drainage among Midwest states based on 2022 Ag Census

Similar to the 2017 Ag Census, the 2022 Ag Census shows that Iowa has the largest acreage of subsurface tile drainage, followed by Illinois, Minnesota, Indiana, Ohio and Michigan (Figure 3). The top ten states with the highest acreage of tile drainage did not change rank in the 2022 census compared to the 2017 census.

Comparison of 2017 and 2022 Ag Census tile data

Even though all Midwest states had an increase in tile drainage from 2012 to 2017, the 2022 census data shows that six Midwest states (IA, MO, IL, IN, OH, MI) had a reduction in acreage of subsurface tile drainage from 2017 to 2022 (Figure 4). Other Midwest states (ND, SD, NE, KS, MN, WI) had a much lower increase in tile acreage from 2017 to 2022 compared to the increase they had from 2012 to 2017.

A total of 48.1 million acres were reported to be tile drained in the Midwest in the 2022 census compared to the 50.4 million acres in the 2017 census. This is a 4% reduction in tile acreage from 2017 to 2022. In contrast, a total of 50.4 million acres were reported as tile drained in the 2017 census compared to 40.1 million acres in 2012, a 14% increase from 2012 to 2017.

Tile drainage has been on the rise

The states showing a drop in acreage of tile drained land from 2017 to 2022 Ag Census present an unrealistic outcome because tile drainage has been going into the ground over the five years from 2017 to 2022.

“Michigan drainage contractors install millions of feet of drainage tile each year, driven by the high demand and favorable results, which has led to a significant increase in tile-drained acres over the past few years in Michigan,” Will Word, a Michigan LICA board member said.

Subsurface tile drainage provides a good return on investment. We expected an increase in subsurface tile drainage from 2017 to 2022 because high-intensity, heavy rainfall has become more frequent, thereby creating an incentive for growers to invest in subsurface drainage. For example, the wet 2019 growing season that prevented planting had some growers invest in tile drainage or split lateral spacing in half.

“Farmers in the Midwest are looking to improve their water management systems to reduce their risks. This means expanding their tile-drained acres and improving their existing drainage systems,” Keegan Kult, Executive Director of Ag Drainage Management Coalition said. 2022 Census

Possible reasons for the unexpected tile result of the 2022 Census

The response rate for the 2022 Census was 61.0%, down from the 71.8% response rate of 2017. NASS uses a statistical method to correct the data for things such as nonresponses (people not returning their census questionnaires) among others. NASS explains that the relative reliability in their corrected data is quantified by the Coefficient of Variation (CV), which ranges from 0% to 100%. The greater the CV, the greater the uncertainty in the corrected data. In 2022, the Midwest states had an average CV of 14.9% (ranging from 2.2% to 86.8%) for acreage of tile drained land, whereas this value was lower (meaning less uncertainty) in 2017 at 7.0% (ranging from 2.2% to 23%). Out of all the Midwest states, Michigan had the highest CV of 86% in the 2022 tile acreage data, which means that Michigan’s 2022 data has a low reliability.

Another reason for the unexpected outcome of tile acreage may be the reduction in acreage of cropland harvested in every Midwest state in 2022 compared to 2017. The Midwest reported 303.1 million acres of harvested cropland in the 2012 census, followed by an increase to 306.3 million acres in 2017, and followed by a decrease to 296.7 million acres in 2022. This shows that harvested cropland shrunk by about 9.6 million acres from 2017 to 2022. We recommend further investigation to find out why the 2022 Ag Census data shows an unexpected result for tile drained land. 

Summary

The tile drainage acreage reported in the 2022 census is unexpected, especially in the states with reduction of acreage. Whether this is caused by the lower response rate of 62% in 2022 compared to the 72% of 2017 or other factor, understanding the reasons is crucial to ensure the data can be used in decision-making.

Even with the unexpected 2022 tile acreage data, the distribution and proportion of harvested cropland with tile drainage shows that subsurface drainage continues to play a significant role in crop production in the Midwest. Without subsurface drainage, crop production would not be able to meet the growing food demand because of poor crop yield due to excess water. Although drainage is required for crop production, it also transports nutrients off the farm; that is where phosphorus reduction and nitrate reduction strategies come into play.