Research has shown that the optimal whole-plant moisture range for silage is 62% to 70%. For best results for upright silos, levels should be between 65% to 70% moisture, bunkers and piles at 63% to 68%, and silo bags at 60% to 65%. Harvesting too wet (more than 70%) can cause seepage, poor fermentation, and unwanted clostridia growth. Harvesting at too dry levels (under 60%) can reduce packing efficiency, boost kernel shatter, and take a toll on fermentation.
“It takes roughly 42 to 48 days for most corn hybrids to reach from silking to mid-dent (R5.5) stage, and be at 65% to 70% moisture content,” Kaur said. “It would also coincide roughly with the 50% kernel milkline; however, this relationship has become increasingly debatable with newer and stay-green hybrids. Therefore, it becomes critical to sample the crop and directly measure percent dry matter for the whole plant.”
Dry down rates are not linear and may vary with temperature, solar radiation, hybrid traits, and plant health. After pollination, plants typically lose 0.5% to 1% moisture per day. Hot, dry conditions can deplete moisture from 70% to 60% in less than 10 days, while wet or humid weather can also hinder progress.
Kaur gave a few steps to keep tabs on moisture and dry down trends:
- Start sampling at around 1/4 milkline. Take plant samples at random spots from the field at the normal chopper length. About three to five plants from each representative field area does the trick.
- Chop the samples down so that you can draw a sub-sample from them.
- Weigh the sub-sample.
- Heat the sub-sample in the microwave for five minutes.
- Weigh the sample again.
- Reheat the sample in the microwave for another five minutes and weigh again.
- Repeat Step 6 until the two consecutive weights are equal.
- Subtract the final weight from Step 3 to estimate the water weight in the sample.
- Moisture content is then estimated by dividing the water weight by the sample weight from Step 3.
- Repeating Steps 1 and 9 weekly will give you an estimation of dry down rate to help plan harvest timing.
For 2025, several risks could impact harvest, including rapid dry down from heat, tar spot or other foliar diseases accelerating maturity, ear rots producing toxins, lingering smoke haze speeding up dry down, and lodging from late-season storms.
To ensure that you are harvesting your silage crop at the correct time, begin sampling early. This allows you to have a general idea of where your silage is at and lets you begin to prepare your storage and ensiling systems ahead of time.
