by Shelby Gruss
I’ve been sitting on the edge of my seat, waiting to get into the field to harvest my silage research plots. In late August, I noticed so many fields being harvested for silage, but then the rain started. Now, driving across the state, there are half-harvested fields and fields that were set for silage still standing.
This was particularly evident over Labor Day weekend. I noticed a chopper running, though it was probably one of its last passes as I headed into a rainstorm. Driving by that same field last week, it was still only partially harvested.
This is a hard situation many farmers are facing right now. The longer the crop sits in the field, the more mature the plant gets, and the drier it will be at harvest.
Proper moisture matters
When we make silage, we target a moisture content of about 60% to 70%, although the ideal range depends on storage:
- upright oxygen-limiting silos — 55% to 60%
- upright stave silos — 60% to 65%
- bags — 60% to 70%
- bunkers — 65% to 70%
This range strikes a good balance of proper fermentation without heating or leaching. It also helps with packing and excluding oxygen, which is invaluable to the fermentation process.
Our goal is to grow lactic acid bacteria, which need an anaerobic environment. Lactic acid bacteria produce lactic acid, which drops the pH of the silage. Without that pH drop, we face the risk of undesirable bacteria taking over.
What can we do?
Many fields are probably in the situation where the crop is too dry. Dry forage is much harder to pack and exclude oxygen from. Here are a few options to work around it:
Reduce chop length and check kernel processing. The kernels will have more starch, but they also are harder at this point. Checking for good processing is essential to make sure that starch is available to the animal.
Chopping finer may seem concerning from a ration standpoint, but it helps with packing density, and good packing is what gives you quality silage at feedout.
Add moisture back. It takes about 7 gallons of water to raise moisture content 1% per ton of silage. This gets water-intensive fast.
For example, if your corn is at 50% moisture and you’re trying to reach 60% on a 10-acre field yielding 10 tons of dry matter per acre, you would need 70,000 gallons of water.
If you have that capacity, it can work, but dry corn needs time to absorb the water. Supplying that volume fast enough to keep up with harvest is difficult. Four ways to make it easier include:
1. Blend in a wetter forage. If you have wet-harvested alfalfa, sorghum silage, or sorghum-sudangrass available, blending can help balance moisture. Getting the moisture right is tricky, and because moisture does not move easily through a silage pile, thorough mixing is important.
If harvesting a late alfalfa cutting, check out these guidelines on timing for stand persistence from Iowa State University Extension and Outreach.
2. Pack well and seal tightly. Use heavy equipment when packing, and do not pack more than 6 inches at a time. Cover tightly with plastic or an oxygen barrier to keep the environment as anaerobic as possible.
3. Consider an inoculant. Inoculants will not fix a moisture problem, but dry silage that is hard to pack is prone to heating at feedout. An L. buchneri product produces acetic acid that inhibits the yeasts and molds behind that heating. Just plan on extending time in storage before opening, since it needs that time to work.
4. Give it more time in storage. This is the one adjustment that costs nothing. Bacterial activity during storage breaks down the prolamin protein matrix surrounding the starch granules, which improves ruminal starch digestibility — the same process that makes the hard, mature kernels in dry silage more available.
With drier corn silage, leaning on extended storage time is a way to recover some of that energy. If you have the inventory to leave the pile closed longer, do it. This pairs well with the inoculant above; both are asking for the same thing: leave it shut.
What to expect at feedout
Even with good management, drier silage will feed differently, and it is worth flagging before you’re standing at the face in January. Here’s what to expect:
The fiber will be less digestible. More mature corn silage carries more neutral detergent fiber, and more of that fiber is lignified, which means less of it is available to the animal.
Nutritionists working with dry corn silage often recommend adding nonforage digestible fiber sources such as soy hulls or corn gluten to make up the difference. This is a discussion worth having with whoever balances your rations before you open the pile.
Watch the feedout face. A pound of dry corn silage contains more dry matter than a pound of wet silage, so the face moves more slowly through the pile, which means more oxygen exposure and more opportunity for mold and yeast growth.
Keep the face fresh, remove spoiled material from the top layer and shoulders, and check that your feedout rate is keeping up.
Stalk quality and contaminants
The wet conditions this fall have led to stalk quality issues and greater potential for contaminants. Watch for stalk and ear rots, which can produce mycotoxins in the silage.
Fermentation does not lower toxin concentrations, and dry corn silage is especially prone to mycotoxin issues.
If you suspect a problem, work with a nutritionist on whether binders or neutralizers make sense in the ration.
More information on stalk and ear rots that can cause mycotoxins is available from the Crop Protection Network.
Areas with flooded ears, where ears have been submerged, are considered adulterated by the U.S. Food and Drug Administration. More information on submerged grain from ISU Extension is available.
Gruss is an Iowa State University Extension and Outreach forage specialist.