Timing for planting corn for silage varies tremendously as you move north to south or east to west. As a rule of thumb – the earlier the better. It’s best to get corn silked and grain filled before hitting the peak of the summer heat and/or the dry spell of the mid-to-late summer.
“However, when growers are forced into later planting, there are some scenarios where grain can be lost with every week we plant later after a specific date, and that date is going to vary depending on where you are located,” said Dr. Kraig Roozeboom, agronomy professor at Kansas State University. “But for much of the silage growing area, by the time you’re getting past early to mid-May, you’re starting to lose yield.”
Growing Degree Units
The growing degree units (GDUs) for a full- or medium-maturity hybrid is about 2,800 GDUs to achieve physiological maturity. The difference between three-quarter milk line and physiological maturity is only a few hundred GDUs, depending on hybrid maturity. This could equate to days or weeks, depending on location.
“If you’re in the Northern Corn Belt where dry down is really slow and the temperatures are dropping off, it could take a long time to accumulate those last few hundred GDUs to reach physiological maturity,” said Roozeboom. “It could be several weeks earlier than you would harvest corn for grain, so you’re gaining some time that way.”
However, it all depends on the growing season. Kansas State University conducted research several years ago focused on central and eastern Kansas.
“There were some years that the later you planted you took a hit on yield pretty drastically, and there were some years where planting date actually had no effect,” Roozeboom said. “We could plant in some of our environments until the Fourth of July and have no impact on grain yield, and that’s fairly correlated with what a silage yield would be like. There were the occasions where later planting increased yield because of the year we had. Maybe there was some early-season stress that was avoided by planting a little bit later. Late planting does not always, 100% of the time, hurt yield.”
To maximize quality, growers should cut corn silage between one-quarter and three-quarters milk line. Grain is an important component of high-quality silage, so try not to cut the grain silking period off too much more than you would for a typical grain crop.
“By the time you’re getting to 50% milk line, which is the middle of the dent stage, you’ve accumulated a lot of kernel dry matter, but depending on moisture and nitrogen, there’s still a fair amount of green leaf area and the plant is just starting to senesce,” he said. “If you harvest too early there’s too much moisture and your ensiling process will not go well.”
Environment plays an important role in quality. If it’s been a tremendously drought-stressed season, cut corn for silage earlier when it’s starting to dry down and senesce.
“You don’t want corn for silage to get too dry, and we run into that in Kansas quite often,” Roozeboom said.
Unless you’re extremely late, a change in your hybrid maturity should help reduce any impact from what a normal corn silage planting will yield.
“It’s a continuum, and the northern-tier states are going to be impacted less so, and then as you move into the southern states you could probably plant by the end of June, and given the right conditions you could still produce a reasonably good silage crop,” he said. “However, the South tends to get more heat, which helps move the corn along, and the impact of a late planting gets to be a bigger deal because, depending on when that heat comes, it can really drive down yields.”
When heat occurs right around silking and pollination, early grain fill can be a problem. Heat also speeds up the plant development, so the plant doesn’t grow as big, which means it’s not accumulating as much biomass; therefore, vegetative and grain yields go down.
“In the South, it’s too much heat, or when the heat hits, that can damage the yield. In the North, you just run out of growing season,” Roozeboom said.
He said some growers in Kansas are double-cropping corn in late June to early July after wheat harvest.
“We’re talking maybe 80-bushel corn, and that’s quite different than the 200-plus-bushel yields that growers get in the heart of the Corn Belt, but it’s a very different environment with different expectations,” he said. “They’re putting a lot less into the crop in terms of nitrogen and seed. We’ve done work looking at planting dates and seeding rates as well. If you’re planting late, you might want to consider bumping up your seeding rate, but make sure you have the moisture available to support an increased seeding rate.”
Headline image courtesy of Kansas State University