Harvesting corn silage at the right time for best livestock performance requires diligent monitoring of the crop’s moisture content, say forage experts at Pioneer Hi-Bred.

“Start walking fields and assess kernel milkline levels about four weeks after silking,” says Bill Seglar, Pioneer nutritional sciences veterinarian. “Milkline levels provide a quick way to visually inspect the plant's maturity.”

When corn shows some dent on the ear, it's time to walk fields and find samples to achieve ideal dry matter at harvest, he says.

“To check milkline, first break an ear in half. Use the outer half of the ear. Remove a kernel. Either bite into the tip of the kernel or poke a knife blade or pin into the bottom and push upward until the point meets resistance. The milkline is the area from the point of resistance to the crown. One-third milkline represents 68-72% while two-thirds milkline represents 63-68% moisture.”

Although some research suggests that milkline as a weak indicator of actual dry matter, it complements lab testing. Milkline also can be used as a signal to start sampling dry-matter levels. Dry-matter lab tests may provide the most accurate results. Seglar suggests collecting a minimum of 10 plants per field location to sample.

“Comparing a chipper-shredder lab sample to a grower's own silage samples helps build the data needed to make informed harvesting decisions,” says Bill Curran, Pioneer research scientist. “Any dry-matter test is better than guessing. It's worth the extra effort to make sure producers get the most out of their investments.”

Knowing individual field conditions and hybrid maturities also can help growers pick the appropriate harvest date. Experts recommend walking fields to examine crop maturity levels as harvest nears, helping determine if crops are on target for the expected harvest date. Under normal conditions, the tasseling date can serve as another way to check harvest timing.

“Harvest is typically six to 10 days away when the crop is about 3-5% wetter than optimal,” Seglar says. “Yet, it's not a hard-and-fast rule. Outside factors such as weather and field location can affect the rate of maturity and ideal moisture levels for harvesting forage.”

If growers allow corn to reach 63% moisture in the field, they have the opportunity to maximize starch and tonnage yields, says Curran. Harvesting below that moisture level can lower silage quality. Early harvested corn silage will be lower in starch and higher in neutral detergent fiber. Seglar says modern hybrids with strong late-season agronomics tend to retain fiber digestibility within the 63-70% moisture range.

Planting hybrids with a diversity of maturities is another way for operations with many acres to manage harvest timing. Staggering maturities can help hit quality and dry- matter targets on more acres, says Curran.

“Consider a five- to seven-day range between hybrids to allow for a shorter or wider harvest window,” he advises.

Get corn silage troubleshooting tips from Hay & Forage Grower, Parts 1, 2 and 3.