By Marilyn Thelen, Michigan State University Extension
June 1 has come and gone and about 10 percent of the corn is still in the bag. At this point, the question becomes, "How late can corn be planted?"
Nearly 50 percent of Michigan’s corn was planted the week of May 12, 2013. Producers waiting for acceptable field conditions took advantage of the one week in May with dry weather to take corn planting progress from below normal to above the five-year average (according to the May 28, 2013 Michigan Crop Weather). Since that time, it has been a struggle to get in the field.
With the arrival of June 1, we must consider the probability of corn reaching maturity by harvest and the other options that may be available that could minimize our risk in the fall.
Here are a few factors to consider.
How many growing degree days (GDD) remain?
Corn development is measured by the GDD from emergence. Since each year is different, the calendar is not the best tool for measuring corn development. In addition, corn development ends with the first killing frost in the fall. So, let’s say we are able to get back in the field on June 1 (tomorrow, as I write this article) and the corn emerges June 4. Since most hybrids will need 1,100 to 1,200 GDD to reach the silk stage, using a five-year summary of GDD at the Ithaca Enviro-weather station, corn will reach the silk stage by around July 25 in a warm year like 2012, but in a cool year, like 2009, corn would not silk until about August 10.
It takes another 1,100 to 1,200 GDD from silk to maturity. Again, using the five-year average for GDD accumulation, in a warm year the corn has a chance of reaching maturity, however in a cooler year with an early frost, corn will not. There is a 50 percent probability of a killing frost in Michigan, determined based on 30 years of data (1961-1990) as early as September 29. To see the progress of GDD in your area, visit Michigan State University’s Enviro-weather site.
Yield of late planting
Studies in Wisconsin have shown that the yield of corn planted in early June decreases at a rate of 3 percent for each day planting is delayed. Pair with the risk of an early frost and growers may want to look at changing to another crop.
Harvesting the corn as silage may be an option. 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 a yield 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 grain quality will be impacted if the summer remains cool and, we have lower GDD accumulation or we have a killing frost prior to maturity. In this case, the corn will have lower test weight, higher moisture and will be more susceptible to ear molds. Depending upon how the corn develops, harvesting as a high moisture corn may be a way to minimize risk.
According to University of Wisconsin Extension’s "Alternative Forage Crops", corn silage planted June 1 and harvested mid-September yielded 14 to 17 tons 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 RFV.
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.
Switching out of corn
Producers should also consider switching to soybeans as the planting date extends into June. See the Michigan State University Extension article "Management tips for late-planted soybeans" for more details.
Forages are short as a result of the 2012 drought. Producers that need forage, or have a local outlet, may consider planting an alternative forage. Forage sorghum, Sudan grass and Sorghum-sudan hybrid are all options that can be planted in June and July, as recommended by "Alternative Forage Crops."
Producers with crop insurance should also be aware of the final planting dates for prevented planting. In Michigan, the final planting date for corn is June 5 and for soybeans is June 15. For all your options, see Crop Insurance and Prevented Planting, USDA. When considering prevented planting, always check with your crop insurance provider to see how it impacts your coverage.
Options for planting corn and soybeans in Michigan after June 1 are still viable. Care should be taken to select the proper day hybrid, or change to a crop that offers less risk such as corn silage, alternate forages or soybeans.