Wet and cold conditions have become more of a norm in Wisconsin in the recent years, which has come to inhibit planting progress more often than not. Corn farmers have begun to ask how to manage corn for silage as planting is delayed.
Planting dates for corn silage is somewhat dependent upon what the producer is looking for. Milk per Ton, or quality, is not affected by planting date as much as Milk per Acre, or quantity, due to the forage yield impact (Figure 1).1 The optimum planting date for Milk per Acre is the same as that of corn grain, or May 1, for southern Wisconsin and May 7, for northern Wisconsin.2,3 The date when maximum forage yield (tonnage) occurs is April 24.
The optimum planting window for corn silage ranges from April 10 to May 15 (Figure 2).1,4 If the range of optimum is exceeded however, what can producers do to make the most out of a less than ideal situation? In short, 95% of maximum yield can be achieved using full-season products through mid-May. Producers should target May 15 as a switch date for increased Milk per Ton and May 20 as a switch date for increased Milk per Acre (Figures 4, 5).5 Now let’s find out more details.
Figure 1. Corn forage Milk per Ton and Milk per Acre of full-season hybrids (104-108 RM) to planting date during 2003-2012 at Arlington, WI (N = 235 plots)
Figure 2. Corn forage yield response of full season hybrids (104-108 RM) to planting date during 2003-2012 at Arlington, WI (N = 235 plots).
As the calendar turns from mid- to late-May, producers typically turn to shorter maturing products. When corn is intended for silage or high-moisture grain, switch dates can be later than that of corn grain because of less concern around drying costs and getting the plant to physiological maturity.5 Southern Wisconsin has greater flexibility than northern Wisconsin with up to 4 possible switch dates, while Northern Wisconsin has only 1 or 2 switch dates (Table 2).2,3,4
Table 2. Relative maturity of adapted corn hybrids for different planting dates and relative maturity zones. Derived from UWEX A3353 - Corn Replant/Late-Plant Decisions in Wisconsin.
Full-Season Relative Maturity Zonea | b for Late Planting |
May 20 | June 1 | June 10 | June 20 |
85 and earlier | 75 to 80 | 75 to 80 (silage) | ---- | --- |
80 to 90 | 80 to 85 | 75 to 80 (silage) | --- | --- |
90 to 95 | 85 to 90 | 75 to 80 | 75 to 80 (silage) | --- |
95 to 100 | 90 to 95 | 80 to 85 | 75 to 80 (silage) | --- |
100 to 105 | 95 to 100 | 85 to 90 | 75 to 80 | 75 to 80 (silage) |
105 to 110 | <100 to 105 | 90 to 95 | 80 to 85 | 75 to 80 (silage) |
110 to 115 | 105 to 110 | 95 to 100 | 85 to 90 | 75 to 80 (silage) |
In terms of quality and digestibility, planting date has mixed effects. The size of the “plant factory” is not affected by planting date. Stover, or number of leaves, size of the stalk, shank and husk is largely controlled by plant genetics, and digestibility remains relatively “flat” or constant across dates1. However, planting date does influence starch, and starch content decreases with
later planting dates, as shown in (Figure 3). 1
Figure 3. Corn forage ivNDFD and Starch content response of full season hybrids (104-108RM) to planting date during 2003 to 2012 at Arlington, WI (N=235 plots).
To further add to this, University of Wisconsin researchers conducted trials that compared corn silage yield and quality of full and shorter-season hybrids between 2003 and 2008. Results from the Arlington Research Station showed that forage yield was greatest with full-season hybrids for early planting dates (Figure 4). The regression lines converged around May 20, but forage yield was not significantly different after that date. Little difference was seen between full- and shorter-season hybrids for digestibility of the stover energy pool as measured by ivNDFD. However, shorter-season hybrids had higher starch content on every planting date, even though grain yield was lower until after May 24 (Figure 5).
When forage yield, ivNDFD and starch content values were used in the Milk 2006 model to calculate Milk per Ton and Milk per Acre, both Milk per Ton and Milk per Acre of full-season hybrids were greater than shorter-season hybrids when planted early. For Milk per Ton, a switch date occurs around May 15, when the shorter-season hybrids have greater Milk per Ton than full-season hybrids.
However, around this switch date Milk per Acre differences between full- and shorter-season hybrids aren’t much different. A slight Milk per Acre advantage is seen for shorter-season hybrids until about June 1, and then the gap begins to widen (Figure 2). By June 12, the difference between full- and shorter-season hybrids is about 2,000 pounds of Milk per Acre, or 10%, favoring early-season hybrids.
Figure 4. Corn forage Milk per Ton and Milk per Acre response of full-season hybrids (104 to 108 RM) and short season hybrids (94 to 98 RM). To planting date during 2003-2008 at Arlington, WI. (N = 324 plots).
Figure 5. Corn forage yield, ivNDFD and starch content response of full-season hybrids (104 to 108 RM) and short season hybrids (94 to 98 RM) hybrids to planting date during 2003 to 2009 at Arlington, WI (N = 324 plots).
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1. Lauer, J.G. Planting Date Effects on Corn Silage Yield and Quality. 4 May 2013. Corn.agronomy.wisc.edu.
2. Lauer, J.G. Corn Late Planting. 21 August 2014. Corn.agronomy.wisc.edu
3. Lauer, J.G. The Best Corn Planting Dates Are Yet To Come. 22 April 2013. Wiscorn.blogspot.com
4. Lauer, J.G. Hitting the Bull’s Eye When Switching Corn Hybrid Maturity. 15 May 2013. Wisccorn.blogspot.com
5. Lauer, J.G. Switch Dates for Corn Silage. 23 May 2013. Wisccorn.blogspot.com.