The key to corn silage decisions is to keep the end in mind. At the end, corn silage should provide a high quality feed to livestock that properly ensiled. To achieve this goal, the harvest process is crucial.
The ideal time to harvest corn silage is dependent on numerous factors, but the most important may be whole plant moisture/dry matter. Most farmers will target a whole corn plant dry matter of 35% (moisture of 65%) for chopping.
| Table 1. Ideal dry matter range of corn silage for various storage structures | |
| Silo structure | Ideal % dry matter |
| Bag | 35-40 |
| Bunker | 35 |
| Upright silo | 35-40 |
Harvesting at the correct moisture will be crucial for achieving good pack density. The whole plant moisture should be between 60 and 70%. Storage structure will impact what end of that range you want to be on. Bunkers or pit silo storage will need to have more moisture to ensure a very good pack. Bagging or upright silo storage can accommodate a little dryer material. Chop length is also a factor. Ensuring chop length remains short is vital to a good pack and proper fermentation of the corn silage.
Determining moisture can sometimes be difficult in the field. One way is to look at the milkline on the corn kernel. A milkline ½ to ¾ the way down the kernel should indicate a whole plant moisture of 70 to 60%. If the corn has black layered, the whole plant moisture is likely under 60%. This may vary depending on hybrid.
Another good way to measure moisture in the field is to grab a handful of silage and attempt to make a ball. If the ball holds shape and there is a lot of free juice the silage is approximately 75% moisture. If the ball holds shape but there is little juice the moisture is likely 70-75%. If the ball falls apart slowly, the moisture is likely 60 to 70% moisture. When the silage will not make a ball for even a short period of time the moisture is poor and likely below 60%.
Target ¾ of the way down the kernel for the milkline. When starting the harvest, check the silage by grabbing a handful and attempting to make a ball. The correct moisture should make a ball that holds and falls apart slowly. If your silage is out of the optimum for moisture, then look into adding an inoculant and potentially a sugar source. Bagging will result in a better chance at proper ensiling than ground piles or bunkers when moisture targets are missed.