Now that the March Prospective planting report has been released, head-scratching will begin about how and where these acres will play out. Then comes the speculation about Mother Nature or Mr. Market forcing producers to call an audible.
Stepping back from the year-over-year shuffle, we recently stopped to consider key trends and shifts in corn and soybean acreage since 2010. This week’s post highlights three of those maps.
Where Soybeans Are King
In 2017 and 2018, the U.S. planted more soybeans than corn. This historically rare outcome has underpinned soybean’s recent boom in popularity. Since 2010, soybeans have, on average, accounted for 47.4% of total corn and soybean acres .
While soybeans have toppled corn acres only twice at the national level, there are regions and counties where soybeans frequently outplant corn. Figure 1 shows soybeans’ share of total corn and soybean acres at the county level. Lighter shades represent counties where corn leads (soybeans’ share <50%), while the darker shades are where soybeans are more popular (soybeans’ share >51%). Soybeans lead the rotation in the Northern Great Plains, in most of Eastern Kansas, the Delta region, as well as areas near the East Coast. Even throughout the Corn Belt, soybeans tend to be more popular in the East – parts of Indiana and Ohio- and less popular in the Western (Iowa and Nebraska).
Which geographies are prone to acreage switching? There are two ways to think about this and how it relates to the acreage battle. The first is which counties have the most variation, measured by the standard deviation of soybeans’ share of corn and soybean acres.
Figure 2 shows the relative basis measure or the standard deviation. The counties are grouped into four quartiles, with the darkest shade representing the most variability.
In Iowa and large parts of Nebraska, the corn and soybean rotation has very little variability. Producers here tend to stick with their rotation. On the other hand, there is considerable switching along the Western frontier of corn and soybean production, as well as in the Delta region and into Kentucky and Tennessee.
The challenge with Figure 2 is that a 1% switch on 100 acres is fewer than 1% of 1,000 acres. In other words, counties with big variability might not equal a lot of acres. On the other hand, the heart of the Corn Belt has a smaller variation, but this is where large corn and soybean acreage is planted. You can read more about this in our full article, but Illinois stands out when it comes to acres worth of switching.
Increased Corn and Soybean Production
Like peeling an onion, each map can lead to another question. At this point, we should stop and consider the increase in total corn and soybean acres. Compared to a decade ago, the U.S. plants roughly 7.8m more acres (+4.6%) of corn and soybeans .
Figure 3 shows where the increase in total corn and soybean acreage has taken place. Each dot represents 5,000 acres. Not surprisingly, The Great Plains again stand out with the biggest county-level acreage gains occurring in North Dakota, South Dakota, and Kansas. Missouri, southern Illinois, Kentucky, Tennessee, and even Ohio saw increases as well. A big source of these additional acres has been the decades-long decline in wheat acres.
Wrapping It Up
Each year, the acreage debate is impacted by a host of factors, including input expenses, crop insurance prices, and the weather. Some of the bigger trends – such as the regions with the most crop rotation variability and where corn and soybean acreage has been added – get lost in the shuffle as they play out slowly over each year.
 Between 2010 and 2012, soybeans accounted for 45.3%, compared to an average of 48.6% between 2020 and 2022.
 Average corn and soybean acre from 2010 to 2012 was 169.0m acres; Average corn and soybean acres from 2020 to 2022 was 176.8m acres.