What a difference a year makes! The 2012 planting season was one of the earliest ever. By this time last year, almost everything was in the ground and we even had some corn emerging that had been planted in mid-April. Pea planting had started last year on March 28 and by now fields were well established and growing aided by the abundant rains we had during the month of May in 2012. The crop conditions by the first of June 2012 were excellent, but that changed as dry weather persisted until late August when some rain fell that helped salvage some pretty good yields around the area. Modern corn hybrids can tolerate very dry conditions, but still need plenty of warm sunshine to produce a good crop.
This year everything is totally different. After a winter of little precipitation, we have experienced an extended period of cold wet weather highlighted by a lot of snow and rain. Of course, we were in desperate need of moisture heading into this planting season and this recharge of the soil moisture is very welcome.
We need two things to germinate corn, moisture and warm soil temperatures. Corn needs a soil temperature of 50 degrees at the 4-inch depth to germinate. This can happen quickly once we have some sunshine and warming wind conditions. We have been used to planting early and getting the corn planted by the first of May. This year will be different.
Tina LeBrun & Wayne Schoper
So what is the penalty for delayed planting of corn? It all depended on how the rest of the planting season shapes up. If we have a warm summer we can catch up in a big hurry. Long-term data indicates that corn yields actually begin to decline somewhat after a planting date of April 25th. That being said, we don't really start seeing a decline in yield potential until after May 10th. This all depends on the summer weather and so much can change with a hot dry summer or a summer that is very cool like July of 2009. The latest date recommended for planting corn in southern Minnesota is June 15. We did experience this in the spring of 2011 when we saw a lot of corn planted well into the month of June. Yields were adversely affected of course and we also had an early frost that didn't help. We can still plant full-season maturity hybrids until the 25th of May.
As for planting depth, with a delayed planting season due to wet and cold field conditions the recommendation stays to maintain a planting depth of 1.75 to 2 inches. If we get shallower than that, 1.5 inches, we can increase the risk for poor establishment of the nodal roots that develop between the seed and the soil surface. Poor nodal root establishment is commonly associated with both shallow planting and a very dry and fluffy soil surface. It can also be associated with shallow planting followed by heavy rains that settle the soil surface, resulting in seed placement that is shallower than originally desired.
So the main message is here is to stay the course and wait until soil conditions are fit before tilling and planting. We are experiencing an old-fashioned late spring and there is not much we can do about it but be patient and wait for warm and dry weather.