by Elizabeth A. Tomlin
“Alfalfa height has been found to be an efficient and reliable indicator for spring’s first cutting,” reported Cornell Cooperative Extension Regional Field Crop Specialist Kevin Ganoe.
Ganoe, who is with the Central New York Dairy & Field Crops Team, spoke to a large audience of crop farmers about the benefits of being able to judge the Neutral Detergent Fiber (NDF) content not only in alfalfa, but also alfalfa grass mixes and grasses.
“Dave Balbian and I started sampling fields in 2004,” stated Ganoe. “We actually sampled the fields taking what is called a ‘scissors cut’ to send a sample to a forage-testing lab to have it analyzed. We did this for a number of years.”
Ganoe credited Dr. Jerry Cherney at Cornell University, who then “came along with research that showed that alfalfa height was a reliable indicator of the NDF levels.”
After looking at data across several Central New York counties for several more years, Ganoe and Balbian also determined that measuring alfalfa height was as reliable — or more so — than sending in scissors cut samples.
“With taking grab samples there is sampling error involved where choosing grass to sample that is representative of the field can be difficult,” said Ganoe. “The only difficulty we have had with using alfalfa height was last year, in 2012, when alfalfa was actually set back by frost, but the grasses were not as strongly affected.”
The only real challenge to the ‘alfalfa height’ method, is when pure grass stands do not have any alfalfa nearby at a similar elevation and soil type.
However, the Field Crops Team will send out an e-mail within a day of gathering information to let people know how the NDF levels are changing, while the lab testing takes longer.
The desired NDF for an ‘all grass’ field is 50 percent, while 50/50 mixed alfalfa and grass fields is 44 percent, and a pure alfalfa stand is 40 percent.
“Predicted days to cut are based on daily NDF increases for grasses of 1-percent point, 50/50 mixed stands of .8 percent point, and pure alfalfa of .5 percent point.”
Ganoe showed three “numbers” helpful in determining NDF content when using alfalfa height as an indicator. Simply use a yardstick for measuring the alfalfa.
“Begin cutting 100 percent grass stands when nearby alfalfa is 14 inches tall for the desired 50 percent NDF,” instructed Ganoe. “Begin cutting 50/50 mixed alfalfa and grass stands when nearby alfalfa is 22 inches tall for the desired 44 percent NDF. And begin cutting 100 percent alfalfa stands when alfalfa is 28 inches tall for the desired 40 percent NDF.”
NDF usually increases approximately 0.8 to 1.2 per day for grasses. Expect the lower end of that range when the weather is cooler and the higher end of the range when the weather is warmer.
In alfalfa, NDF increases about 0.4 to 0.7 per day, again expecting the lower end of that range in cooler temperatures and the higher end in warmer temperatures.
Predictions are adjusted each week considering the coming week’s forecast weather.
“The key to hay crop profitability is in the management of the crop you have,” Ganoe pointed out. “First cutting tends to have higher digestibility than later cuttings, so it’s even more important that we get it done right.”
This also sets up successfully harvesting second and third crop cuttings.
The ‘Spring First Cutting Monitoring Program’ is conducted by Cornell Cooperative Extension of Chenango, Fulton, Herkimer, Montgomery, Otsego,
Schoharie and Saratoga Counties and the CNY Dairy and Field Crops Team.
First Cutting Forage Quality Update weekly reports are available by e-mail. For more information contact Ganoe at 315-866-7920 extension 230, or e-mail firstname.lastname@example.org.
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