By DOUG GRAVES
Ohio Correspondent

COLUMBUS, Ohio — Alfalfa is a relatively easy crop to grow, but knowing when to make those timely cuts takes a little bit more knowledge.

Alfalfa producers in states such as Wisconsin, Minnesota and New York make use of the PEAQ (Predictive Equations for Alfalfa Quality) method to determine the optimum time to harvest the first cutting of the plant. Now that same technology is making its way into places like Ohio, Indiana and Illinois.
“In Ohio this method of calculation hasn’t been as adopted as readily as in those other states because here in Ohio the rain is such an issue,” said Mark Sulc, professor and forage extension specialist at The Ohio State University. “But it still can be applied and be used as a harvest gauge. Most growers in Ohio are too worried about all the rain, but the PEAQ even works later on in the summer, not just for the first cutting.”

PEAQ uses plant height (measured in inches) and maturity (bud or flower stage) to estimate the relative forage value (RFV) or relative forage quality (RFQ). By determining the RFV of standing alfalfa, producers can more accurately gauge when to begin the first crop harvest.

PEAQ was designed by Ken Albrecht, professor of agronomy and agroecology at the University Wisconsin-Madison. Sulc worked with him on this study and is a believer in this calculation methodology.

“I worked in the laboratory with Albrecht and when we returned to Ohio we coordinated a validation test of the PEAQ and obtained samples from across Ohio,” Sulc said. “This method works very well right here in Ohio. It’s a good gauge.

“Timely cutting is critical for obtaining high quality forage. For lactating dairy cows the optimal range for neutral detergent fiber, or NDF, of alfalfa is around 40 to 42 percent. A producer can quickly and easily estimate the forage quality of alfalfa in the fields using the PEAQ method.”

According to Sulc, the method has been thoroughly tested in Ohio and provides reasonable accuracy for timing harvest operations. It can be used during the entire growing season. He adds that one can use it to monitor alfalfa NDF as the crop develops.

“If the goal is 40 percent NDF in stored alfalfa, then cutting must begin before the standing crop reaches 40 percent NDF,” he said, “because of the effect of harvest and storage losses. In our experiences, NDF concentration of well-made silage is about 2 percentage units higher than the NDF standing crop right before cutting. Changes in NDF during hay curing will be higher. During the spring, NDF increases about five units each week.”

Researchers like Sulc say knowing when to make cuts of alfalfa can mean extra money to producers. With corn grain prices over $7 a bushel, high-quality forage can reduce the amount of corn grain and protein supplement needed as a source of rumen fermentable carbohydrates and protein sources. For each one-point increase in RFV/RFQ, the alfalfa hay equivalent may be worth $1-$1.10 more per ton.

For example, an RFQ of 140 could be valued at $154 per ton, compared to alfalfa with an FRQ of 180 valued at $198 a ton on a hay equivalent basis.
“The PEAQ is a harvest-estimating tool and not meant to replace lab tests after the alfalfa is in the bale or in the silo,” Sulc said. “A lot goes on from the time of cutting until it’s stored.

It’s just a matter of knowing what the fiber level of the crop is as it’s standing in the field. It’s a quick and easy way to get an idea of what shape your field is in.”

As with any planting or harvesting method, there are pros and cons. The benefits of using PEAQ is simple, fast and inexpensive. The method is robust across a wide range of environments, performs well over all growth cycles during a season and there is no time wasted in waiting for results.
The downside is that results are highly dependent on good sampling technique and the equation is calibrated for only pure alfalfa stands. In addition, the method does not work well in fields with poor alfalfa stands or alfalfa that suffers from waterlogging stress. This method also does not provide reliable estimates of NDF in alfalfa stands that are shorter than 16 inches or taller than 40 inches.