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  • Jin Gan

Grass Silage Considerations

Grass Silage Considerations

There are some aspects of ensiling that remains the same regardless if it's corn, grass or alfalfa. However, there are some differences in harvest processes for grass silage.

Harvesting at the right timing

  • Grasses should be cut at the boot stage when the head is just coming out of the whorl.

  • Target is to achieve around 10 - 15% water soluble carbohydrates in the dry matter.

  • Grasses that are rapidly growing tend to have more of those starches and sugars being put into growth and less accumulation. Hence, it is recommended to harvest at about the boot stage.

  • With that being said, because the second cuts and third cuts do not have heads but they are strictly leafy material, therefore, it is recommended to let the grass get to about 12 - 15 inches tall and cut them by height rather than by maturity expectation.

  • On a second cutting or third cutting stand, after 12 - 15 inch growth point, the leaves stop growing and the bottom leaves die off and disease sets in.

  • Cool season grasses will not grow heads again after the first cutting or in a seeding year.

  • The current cutting height recommendation for grass is around 3.5 - 4 inches which is taller than alfalfa because grasses store energy in the base of the stem instead of the roots.

  • Taller cut heights will also reduce dirt contamination as internally, grasses have about 4% ash.

Wide swath

  • Another important thing to note during harvest is to make a wide swath.

  • For grass to dry rapidly, it needs to be spread out over the entire cut area.

  • Most of time, newer conditions will only cover around 40 - 60% of cut area, so too much hay lies on top of itself and insulates itself, thus preventing drydown.

  • If wide swath is used, then silage could reasonably be made either at the end of the same day it's cut or the next morning.

  • A wide swath is what keeps the stomata open so that the moisture can escape.

  • Furthermore, cut forage put down in a wide swath intercepts more sunlight, encouraging drying.


  • For grass forages, both conditioning as well as wide swaths must be used to help faster drying.

  • Tedding will also speed up the drying process.

  • During raking process, rakes need to be adjusted as to not touch the ground if using a poker rake and minimally for a ground driven wheel rake.

  • If you are able to see scrapes in the dirt from the rake tines, then it will add a lot of dirt and stones to the product.

  • If the grass is cut at the right height and spread into wide swath, the grass stay above the ground on the stubble and the rake does ot have to dig into the ground to lift the grass like it would with a windrow that sinks to the ground.


  • It is time to chop when the grass is cut and is allowed to dry to around 60% moisture.

  • At this point, a decision needs to be made on which inoculant to use.

  • It is important to get good coverage when applying inoculants.

  • The Lactobacillus (LAB) plantarum inoculant is very effective on grass silage, which has about 70% response.

  • The inoculant is crucial to the conversion of sugars to lactic acid.

  • LAB should be used at the rate of around 100,000 colony forming units per ton and the coverage target should be to apply it to every side of the chopped leaf.

  • Therefore, it is better to apply it at the chopper than on top of a window or at the bunker as it would only land on the topmost surface.

Packing the silage

  • Best case scenario is when a bunker is filled within one to two days and then it is covered with two layers of plastic.

  • Baleage should be wrapped within 3 - 4 hours.

  • As soon as the bale is wrapped, the temperature will start to fall because oxygen is cut off.

  • Packing silage in the pile, bunker or tube is one of the most crucial way to preserve quality.

  • Good compaction gives faster fermentation action and less spoilage on feedout.

  • If packed well, when the face is open for feedout, oxygen won't move as far into the pile.

  • Packing density recommendations are the same for grass, alfalfa and corn silage - 15 pounds dry matter per cubic foot, which is 45 pounds silage per cubic foot if you have achieved 65% moisture.

  • If the pile is packed properly, you can feel a hard surface when you punch it with your hands.

  • On the other hand, if your hand goes in 1 - 2 inches when you punch it, then it is too soft and oxygen can enter the pile.

Covering the pile

  • After the silo or the bunker is packed, cover it with 2 layers of plastic, make it airtight and put weights on it so it does not get blown away.

  • Line the bunker walls with plastic as well.

  • Ensure the top of silage in the bunker does not dip downward next to the wall so that water doesn't pool up in the depression and seep into the pile.

  • Good face management practices for grass, alfalfa or corn are the same.

  • Maintain a straight face and use a facer that scrapes from the top down.

  • Do not go in with a loader and lift up because it opens the face for oxygen to permeate the silage.

  • Face management is crucial for quality forage at feedout.

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