Establishing alfalfa is not a cheap proposition. And if you don't pay attention to the seeding equipment, you may waste a lot of money.
"Many farmers neglect to calibrate their seeders when they begin seeding in the spring," says Dan Undersander, University of Wisconsin extension forage specialist. "If so, they fail to take into account differences in seed size and may be seeding at higher rates than necessary."
With elite alfalfa seed costing $4.50/lb or more, that can be an expensive mistake. Overseeding by only 10% can mean you're spending several dollars per acre more than needed.
Wisconsin studies show wide differences in seeding rate when seeders aren't calibrated. Researchers used the same Brillion seeder at the same setting to plant 17 alfalfa varieties. The amount of seed planted varied from 15 to 20.8 lbs/acre. That's a difference in seed cost of about $26/acre.
Seeding rates not only vary from variety to variety, but also among lots of the same variety. Seed size among lots can vary from 190,000 to 230,000 seeds/ pound. If you're seeding 15 lbs/ acre, that can be a difference of a half-million seeds.
"Seed size and test weight can account for a difference of four to 15 seeds/square foot, even if the same number of pounds are seeded per acre," says Undersander.
But he's less concerned about seeds/pound than about pounds seeded/acre. Whether you are seeding 70 or 90 seeds/square foot doesn't matter much as far as final stand is concerned.
"But whether you seed 15 or 20 lbs/acre affects your cost," he says. "That makes it critical to adjust equipment for each lot of seed and each season, even if the same variety of alfalfa is planted."
Undersander figures many farmers won't take the time to calibrate a drill or seeder using the manufacturer's recommended procedures.
"But you should at least check the acreage seeded with the first bag of seed. If the seed comes in a 50-lb bag, and your seeding rate is 15 lbs/acre, it should plant three acres. A 60-lb bag of seed should plant four acres."
Measure off the acreage that should be seeded by one bag of seed. If the field is a quarter-mile (1,320') long, for example, step off a width of 99' for three acres or 132' for four acres.
Pour one bag of seed into the hopper and start seeding the measured area. If you run out of seed before the area is planted, you'll need to close down the drill somewhat. If you have much seed left after you've covered the area, you'll need to open up the drill.
If you're sowing prilled or lime-coated seed, you'll need to make drill adjustments. Lime coating apparently makes alfalfa seed "slicker" so it flows through a drill faster. That's contrary to what you'd think would happen, since the coating increases seed size.
"Different coatings can affect flow rate differently," says Jimmy Henning, University of Kentucky forage specialist. "If your drill isset to seed 15 lbs/acre, you may want to adjust it down to 12 lbs with Celpril-coated seed. For Seedbiotics-coated seed, which doesn't flow quite as fast, close down by about 10%. That will get you pretty close to the proper seeding rate, and you can fine-tune as you go.
"The bottom line: You should check the equipment calibration for the seed you're using - whether it's coated or not," says Henning. "Make sure you're putting down enough seed, but not too much."
How many alfalfa plants do you need per acre? That depends on your goal for the stand. Some time ago, Ohio researchers seeded alfalfa in 10-lb increments, from 10 to 50 lbs/acre. Hay yield and crude protein content were virtually the same from the lowest seeding rate to the highest. However, heavier seedings produced finer stems and higher leaf-to-stem ratios.
"Historically, we've said that five healthy crowns per square foot are needed for optimum hay yields," says Henning.
"But stems per square foot may be a more reliable guide than crowns per square foot, as a measure of both yield and quality. Information from several sources suggests that 55 or more stems per square foot potentially have the best yields. When stems per square foot drop below about 39, you may want to think about replacing or improving the stand."