What is the most important factor that will affect the quality of silage corn on your farm? Harvesting the crop at the correct moisture content based on your storage type.
Where to Start: Determine the Ideal Moisture for Your Storage
What size is your storage? Generally, the smaller the silo, the wetter the silage has to be in order to get it to pack sufficiently. Larger silos can store silage at lower moistures because of the shear mass of the silage pile and the compression this causes.
If you have a small to medium tower silo, a rough estimate would be to aim for 65% moisture content. Taller and larger diameter silos can push down to 62% moisture and still maintain good storage. Oxygen limiting silos can go down as low as 56% moisture content due to the nature of how they seal.
For piles and horizontal bunker silos target between 64% and 68% moisture content, with larger piles allowing to go to a slightly lower moisture content. If the silage being added to a pile or horizontal bunker silo is on the dry side, it would be advised to add extra tractors to the pile to ensure proper packing.
See Tables 1 & 2 below for ideal moisture contents for each type of silage.
Table 1. Ideal Moisture content of Silage given type of Storage (Source: OMAFRA)
Determining the Moisture Content of Your Standing Corn
The next step is to determine when to harvest your standing corn. Usually, when the corn reaches the half milk line it is at 65% whole plant moisture. With modern hybrids having better stay green, waiting until the corn is slightly past half milk line will ensure the corn is below 70% moisture.
As harvest approaches growers can also evaluate the condition of the plant. If the plant is green top to bottom, it is likely over 70% moisture. If it is fired up to the cob and the leaves are twisted or wilted and brown, then the plant is likely closer to 60% moisture. The optimal time to harvest is when the top two thirds of the plant is green and the husk on the cob is loose and dry. The cobs at this stage will often be lighter in color and not very green (see picture below).
Generally, you should not be able to ring moisture out of the pith in the middle of the stalk below the cob. The pith can be wet but preferably not juicy.
The top two thirds of the kernel should have solid starch with some milk towards the bottom.
An easy way to test moisture is to squeeze the kernel with your fingers. The top half of the kernel should be firm and lower part should have milk in it. If your corn experienced a frost, the moisture content may be hard to determine. Frost will help the plant material dry down quickly but there can still be a fair bit of moisture in the core of the stalk and in the cob, if the corn was immature at a killing frost.
The most accurate way to determine whole plant moisture is by chopping 4-6 representative stalks from your corn field and drying the sample to determine the moisture content. This can be done with a microwave, Koster tester, or sending the sample to an accredited lab.
Tips for Fine Tuning Your Silage Harvest
- If the silage is wetter than expected, whole plant moisture will drop around -0.5% per day. This can range from 0% on cool wet days to over 1% on hot dry days. For example, if your silage is at 70% moisture today, it would take 7-10 days to get down to 65% moisture.
- If the crop is harvested with high moisture conditions, increasing the chop length of the cut can reduce how tightly the silage packs preventing seeping.
- If the silage is drier than expected, adding extra tractors to the silage pile or bunker can help with packing.
- If your silage is drier than expected, decreasing the chop length can help the silage pack tighter. Always consult your nutritionist for your preferred chop length for your herd.
- Generally speaking it is not feasible or recommended to try and add water to dry silage as a silo is being filled.
- Cutting height can be raised to improve feed quality, digestibility and energy content.