The wet spring forced many Michigan farmers to delay planting. Very few days remain to plant corn for grain and have it reach maturity. However, farmers that are able to use corn silage have a little larger window for planting corn.
So, how late can corn be planted for corn silage? There are several factors to consider.
How many growing degree days (GDD) remain
A 50 percent probability of a killing frost in Michigan was determined based on 30 years of data (1961-1990). In the primary corn growing areas, the earliest probability of a frost was September 29 in Caro and the latest was October 22 in Monroe. In 2009, a record cool year, the first killing frost was October 1. Recent GDD accumulations between July 1 and October 1 range from a low of 1400 (Huron County, 2009) to a high of 1872 (Branch and Cass counties, 2010). Since most hybrids take 1100 to 1200 growing degree days to silk, in a cool year with an early frost, there may be no grain in the corn silage. However, in a warner year with a late frost, like 2010, corn silage could be near normal. To see the progress of GDD in your area, visit Enviro-weather.
Yield of late planting
Corn silage is one of the better forage crops to plant for both yield and quality when faced with late planting conditions. However, there is still a penalty. Wisconsin studies show that corn silage yields from June 10 planting dates were about 30 percent lower than optimal, and by the end of June, the reduction in yield was 50 percent.
Corn silage planted June 1 and harvested mid-September yielded 14 to 17 ton per acre (65 percent moisture) with a relative feed value of 95 to 105 percent. The July 1 silage yielded 5.7 to 8.6 tons per acre with a similar RTV.
Moisture at harvest and storage considerations
When corn is planted late and harvested for animal feed, take care not to harvest too wet by testing dry matter before harvesting. Corn killed by frost in the silk and blister stage may have a whole plant moisture content of 80 to 85 percent. This can impact the fermentation process and decrease feed quality. Care should also be taken to manage silage leachate.
So, how late can you plant corn for forage? The sooner the better, but you can still harvest a crop when planted as late as July 1. Although not optimal, corn silage is a good option for late planting, especially if you are in need of forages.
Visit these websites for more information:
Corn late plant and replant decisions, Mike Rankin, University of Wisconsin Extension
Alternate Forage Crops, Dan Undersander, University of Wisconsin
Potential for Frost Damage and Other Effects in Corn, Michigan State University Extension
Workshops and webinar to help farmers with critical planting decisions, Beth Stuever, Michigan State University