In 2012, most farmers in southern Minnesota and Iowa began full-scale fieldwork during the week of April 10-17, with most of the corn being planted by the end of April. By comparison in 2013, we are not likely to see much full-scale fieldwork across the region until after April 15, and we are probably a couple a weeks away, at a minimum, from seeing a significant amount of corn  being planted. Soil temperatures are still well below minimal acceptable levels for planting corn, and there is still a considerable amount of frost in the ground in many areas. Some portions of southeast and central Minnesota still have significant snow cover to melt.
At the University of Minnesota (U of M) Research and Outreach Center at Waseca, Minn., the average soil temperature at the 2-4-in. level from April 1 to 5 ranged from 30 to 35° F, which is well below the 50-55° F ideal temperature window for corn planting . These average soil temperatures are below the long-term average soil temperatures for early April at Waseca of 38-40° F at the 2-4-in. level, and are well below the 2012 planting zone soil temperatures of 55-60° F in early April.
Early corn planting in the Upper Midwest is usually one of the key factors to achieving optimum corn yields in a given year. U of M and private seed company research seems to indicate that the ideal planting dates for corn in southern Minnesota are typically April 15 to May 5. However, the ideal planting date for corn varies somewhat from year to year depending on soil temperatures and soil conditions. Research shows that 50% corn emergence will occur in 20 days at an average soil temperature of 50° F, which is reduced to only 10 days at an average temperature of 60° F.
Most university and private agronomists are encouraging producers to be patient with the initiation of corn planting in 2013. There is no need to be in a hurry and to plant corn before soil conditions are ready. Planting corn into poor soil conditions increases the likelihood of poor stands, and anytime corn planting in southern Minnesota and northern Iowa occurs before mid-April, the likelihood of potential frost damage increases.
Most of south-central and southwest Minnesota, as well as the western half Iowa, remains in a severe to extreme drought ; however, drought conditions have improved somewhat in southeast Minnesota and the eastern half of Iowa in recent months. Total precipitation at U of M Research Center at Waseca in March was 3.42 in., compared to a normal of 2.49 in., which was the largest monthly precipitation amount since June 2012. Total precipitation at Waseca in 2012 was 9.37 in. below normal, including almost 7 in. below normal during the 2012 growing season. Other areas of south-central and southwest Minnesota received even less rainfall than Waseca in 2012.
Overall, sub-soil moisture remains extremely short in most portions of the region, which could be a concern if dry weather persists later in the 2013 growing season. At many locations in southern Minnesota prior to soil freeze-up last fall, stored soil moisture in the top 5 ft. of soil was in the 1-3-in. range, compared to a normal level of 8-9 in. of stored soil moisture. Due to the very limited amount of soil moisture in many areas, producers are likely to minimize their tillage  trips prior to planting this spring, in order to maintain as much topsoil moisture as possible for seed germination and seedling growth.
Unless conditions turn very favorable in the next couple of weeks, we are not likely to see near as much corn planted in Minnesota by the end of April, compared to recent years. Historically, early planting of corn usually leads to higher-than-normal state average corn yields. In fact, in five of the six years that 50% or more of the state’s corn acres have been planted in April, Minnesota has either set or been close to a record corn yield. In 2010, a large percentage of corn was planted in April, and Minnesota had a state record corn yield of 177 bu./acre. In 2012, a large percentage of the corn was also planted in April, and the statewide average corn yield was 165 bu., even with very dry late season growing conditions in some areas of the state. The biggest wild card in 2013 may be the limited stored soil moisture and dry conditions that exist in many portions of southern and western Minnesota
Editor’s note: Kent Thiesse is a former University of Minnesota Extension educator and now is Vice President of MinnStar Bank, Lake Crystal, MN. You can contact him at 507-726-2137 or via e-mail at [email protected]