March is here, anticipation is building and our fields may dry out soon, if rain holds off. So when should we start planting corn? Normally, we can start rolling whenever soils dry out. However, soil temperature determines corn germination rate. Cool conditions, like we had last year, may substantially retard germination and can put your crop in perilous condition. Furthermore, because corn planting intentions are more modest this season due to lower profit margins, you should have more opportunity and incentive to make sure your crop gets off to a strong start and has the best prospect for optimal yield.
The good thing is, you can easily assess the environment for corn planting by simply measuring morning soil temperature prior to planting. Warm soil temperature is very critical to successful corn germination, emergence and early growth. Soil temperature is the primary factor regulating germination rate, which can affect stand success and plant emergence uniformity, both of which are paramount to high corn productivity. Thus, appropriate early corn planting dates will likely vary considerably from year to year, depending upon seasonal temperature, rainfall and other environmental conditions. Corn seed germination requires a minimal soil temperature of at least 50 degrees F and germination rate increases substantially as temperature rises. Soil temperature is far more important that of the air, because the corn growing point in underground until the V6 growth stage, which is normally at least 3 weeks after emergence. Thus, the best guideline for determining earliest planting date is when morning soil temperature at a 2-inch soil depth is 55 degrees F and/or at least 50 degrees F at a 6-inch soil depth. These levels generally ensure plant emergence within two weeks.
Although early planting is a critical component of successful corn production, planting corn exceptionally early doesn’t offer much opportunity for enhanced productivity. Remember, corn growth during the entire season is determined by heat unit accumulation measured as growing Degree Days at a 50 deg F baseline (GDD50’s). So what does this mean? Most corn hybrids take about 2950 GDD50’s to reach maturity, and during the summer we accumulate nearly 30 GDD50’s per day. So planting the first 15 days of March, when normal daily GDD50’s average less than 3 per day, is not going to influence crop maturity very much. Conversely, the effect of planting date on potential corn productivity becomes much more significant as the planting window progresses towards the later stages.
Soil conditions, including temperature and moisture content, are the critical environmental factors critical to achieving a vigorous and healthy corn stand. Of course, if we have an extraordinarily warm spring, like 2012, then I highly recommend taking advantage of those conditions to plant your corn crop and hopefully reap the rewards. However, there is little need to get particularly anxious about planting corn based upon the date in March, if planting conditions are not favorable.