It can be hard to see on the calendar that it’s planting time, but that your fields look as if they aren’t quite ready. Proper planting and field conditions, as compared to planting date itself, can often be more important factors to look for as planting season arrives, and the data tells us as much.
For optimum results, look for a well cultivated seedbed with soil temps of at least 50 degrees F at a depth of 2 inches. This is the temperature that a corn seed needs to get the germination process and seedling growth started.
Based on millions of acres of real-world, aggregated soil temperature data from Minnesota in 2017, the highest average yields occurred when soil temps at planting were between 49-55 degrees F.
But do you have to wait for 50 degrees? Not necessarily.
Soil temperature data from Illinois in 2017 shows that while average yields were slightly higher when corn was planted at soil temps between 52-55 degrees F, they were only 2 bushels behind the leader when planted at 46-52 degrees F. This can probably be attributed to plantings that occurred as soil temperatures were rapidly increasing. Soil temperature varies throughout the day, and as days begin to warm up, seed zone soil temps begin to stay above the 50 degrees F range for longer periods.
Yield decreases at higher planting temperatures (above 55 degrees F) could also be attributed to a shorter overall growing season. We have heard from many farmers that there is a tradeoff they regularly consider - wanting to plant earlier to allow for a longer growing season, but not so early that the soil isn’t ready for seed. But if you wait too long, you could risk shortening the growing season too much.
Keep an eye out for soil temps that are quickly approaching 50 degrees, temperature-wise, to find a solid planting window.
Soil moisture adds in another important consideration.
In cold soil conditions (below 50 °F), seeds are more likely to take up water, but not initiate growth, leading to possible seed rot and poor emergence. Another concern is imbibitional chilling injury, which is what happens when seeds take up water that is colder than 40 degrees. This can lead to deformed plants and uneven emergence.
With this in mind, it’s easy to see that holding off until conditions are dry enough for planting into good conditions is a significant concern when looking at cold soils.
While warmer, drier soils are ideal, cooler dry soils come next. Planting into cooler soils means slower germination and emergence, but as long as moisture isn’t an issue, planting a few days earlier when it’s cool could make little difference in how well the crop will proceed the rest of the season.
Planting data above is based on real-world farming data. Information on seed hybrids has been aggregated across millions of acres of data from 2017. Maturity range includes 108-114 days in Illinois and 93-106 days in Minnesota.