There isn’t an exact date that’s always optimal for planting. Wouldn’t it be nice if there were? Instead, you have to do your best to plant into the best possible field conditions. To get your corn crop off to the best start, you generally want to look for soil temperatures (at seeding depth) of at least 50 Fahrenheit, or quickly approaching 50 F, which is the temperature needed to start the germination process in corn.
As you can see from anonymously contributed 2018 FBN member data from North Dakota and South Dakota, the highest corn yields in FBN were observed when planting occurred at soil temperatures between 58-61 degrees.
In Illinois, FBN farmers saw highest yields when planting in the 52-55 degree soil temperature range, and in Minnesota, corn yields were highest on fields planted at soil temperatures below about 60F.
Soil temperature varies throughout the day, and as the days begin to warm up, soil temps begin to stay above 50F for longer periods of time. The key is finding the balance — planting early enough to allow for the most growing time possible, without planting so early that growth is inhibited.
As long as you’re seeing soil temps that are moving into the 50 degree range and looking to stay there or increase, you should be in an excellent planting window based on soil temperature.
In FBN, you can see tens of millions of acres of data on yield by soil temperature at planting and by variety.
The planting data above is based on real-world farming data. Information on seed hybrids has been aggregated across millions of acres of data from 2018. Maturity range includes 108-114 days in Illinois; 93-106 days in Minnesota; 83-98 days in North Dakota; and 93-105 in South Dakota.