Corn Silage: New Ruler of the Bunk?

April 22, 2015 01:38 PM
Corn Silage: New Ruler of the Bunk?

Alfalfa has been called the Queen of forages, but corn silage may be the new King.

Feeding high quality forage is a key to success for dairy cows, without it production and reproduction suffer.
A variety of forages can make up a ration. Bill Mahanna, global nutritional sciences manager for DuPont Pioneer, outlined how corn silage is starting to rule the feed bunk at the Western Dairy Management Conference earlier this spring.
“Really what I think is that corn silage should be thought of as the KING of forages,” Mahanna says.
Alfalfa has fallen in popularity in the U.S. the past 15 years as less tons have been harvested. Forage sorghums have seen an uptick as of late because of water concerns. All the while corn silage has continued to proliferate in production.
Mahanna says corn silage offers high dry matter yields and high starch. When compared with alfalfa, corn silage has much less variability in fiber digestibility. Come harvest time there is less labor involved with corn silage because there is only one cutting. Not to mention more manure can be taken off the dairy and then spread onto the fields for fertilization of corn.
Genetics has aided corn to become the dominate commodity crop. Since the 1950s, kernel weight has steadily increased while late season plant health has improved. Seeding rates have also helped increase annual yields approximately 1.2 percent since 1985.
“Really handling higher population rates is the main reason we’re seeing increased yields,” Mahanna says.
New plant genetics have allowed planting corn at higher densities per acre. Modern corn hybrids have a more vertical upright leaf structure that allows increased solar radiation capturing.
“We have not improved the individual corn plant all that much. What we’ve done is we’ve allowed the corn plant to handle the stress of packing a whole bunch of them into an acre. That is where most of the yield is really coming from,” Mahanna adds.
The same holds true for corn silage. For optimal growth corn plants prefer many days of light intensity, moderate rainfall and very few days that are cloudy or hazy.
Mahanna says the success of a corn silage crop comes down to two factors: hybrid selection and harvest timing.
 Hybrids with much improved late-season plant health are available that allow the plant to continue photosynthesis in the field and add more starch.
“As we harvest later we’re going to be depositing more starch. Starch is a major contributor the increased yield obtained with slightly later harvest timing ,” Mahanna relates.
Soil moisture is the ultimate determining factor for corn growth. Drought stress in the vegetative state of the plant will shorten the plant and impact tonnage; however this early moisture stress significantly increases fiber digestibility.
Lack of moisture later in the plant’s development (from the tassel to ear fill stage) won’t impact fiber digestibility. But it will decrease starch content and impact overall silage yield.
Moisture stress through the growing season will result in shorter plants, smaller ears and fewer kernels per ear.  “All of these are bad for corn silage,” Mahanna says.
A study from 2013 conducted at DuPont Pioneer’s LaSalle, Colo. research station showed the timing of drought stress can have a major impact on plant development. Corn with access to full water averaged 226 bushels/acre. If the stress occurred at the vegetative state, the plant grew shorter and yielded 164 bushels/acre. When stressed at the flowering stage it dropped to 138 bushels/acre. Grain fill stress saw a mark of 127 bushels/acre.
Producers can take steps to mitigate water use through improved tillage practices that conserve soil moisture or better controlling weeds.
Selecting drought tolerant hybrids is also an option as more of these hybrids reach the marketplace. 
Mahanna adds breeding for drought tolerance is a quantitative trait in corn. “If you think breeding for yield in corn is complex, try adding drought [tolerance] on top of it,” he says.
Characteristics of drought tolerant strains include minimal leaf-rolling, better stay-green when stressed and minimal leaf firing.
For those who irrigate, it may be time to consider an alternative system. Mahanna visited a dairy in New Mexico utilizing drip irrigation on all of the alfalfa fields. The dairy located near the Mexican border was using the same amount of water with about 30 percent more yield.
“We know how to irrigate corn for grain yield, what we don’t quite have figured out is how to irrigate for silage to balance yield and fiber digestibility,” Mahanna relates. He thinks there is potential to pull back on water use during the vegetative stage without shortening the plant too much and possibly increase fiber digestibility.
This would conserve more water for the corn to utilize during the reproductive stage when starch is being laid down.
However, there needs to be more research done in growing corn for silage. “We really don’t have enough data on how to irrigate a corn plant for silage production. A lot more needs to be done,” Mahanna says.

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