Frost seeding is a good way to improve a pasture or for seeding cover crops. A handheld broadcaster or a broadcaster mounted on an ATV is an easy way to get the job done. If you are thinking of trying frost seeding with a broadcaster for the first time you should know that calibrating your broadcaster is a really good idea, just like you would do for your seeders and sprayers. Calibration will ensure you get the desired amount of seed on your fields: this is important if you have multiple fields and you have spent the time calculating how much seed you would need to buy. It would be less than ideal if you ran out before all your land was covered or if you had lots of seed leftover.

To calibrate a broadcast seeder, you take a small area in the field (fraction of an acre or hectare) and figure out how much seed needs to be broadcasted over that area to achieve our desired per acre seeding rate and then you do a few practice runs to make sure the ATV speed and broadcaster opening are set correctly. Below are some helpful tips/steps when calibrating your broadcaster.  (The math is done in both imperial and metric, although doing the math in metric is usually easier in the long run to avoid tangling up units.)

  1. Figure out what your spreader width is.

 This will vary depending on seed type. For instance, a clover seed is small and fairly dense relative to grass seed which is fluffier and lighter. Clovers, because they are heavier than grass will throw farther for the most part. At Perennia, we recently calibrated our broadcast spreader, and thought you might find some of the data helpful to guide you in decision-making.  We calibrated with a few different types of red clover, two different varieties of annual ryegrass, and fall rye, plus a blend.  The LowBoy annual ryegrass seed was a bit denser and not quite as ‘fluffy’ as the Rootmax annual ryegrass so it spread further.

Picture above: seed distribution after running seed through the spreader with the ATV stationary. This allowed us to measure the width of our swath.

  1. Figure out what your seeding rate is.

 For this example, we want a rate of 6 lb/ac of red clover (6.75 kg/ha).

  1. Chose an area to do your calibration.

For example, our ATV spreader covers a width of 7m (~23 ft) with red clover seed and we marked out a length of 30m (98 ft).  That means that we are going to do our calibration on 2,254 ft2 (23 ft x 30 ft) which is 0.052 ac (or 210 m2 or 0.021 ha). I would recommend choosing a distance of at least this size.

  1. Figure out how much seed you would need to cover that area.

 We calculate this by multiplying our per acre rate (6 lb/acre) by how many acres we are doing (0.052 acres) our calibration on.  To cover our 23 ft x 30 ft area, we would need 0.312 lb (~5 oz) or 141.8 g of red clover seed. Weigh out 4-6 ziploc bags of that seed amount so then we can do multiple calibration runs if needed.

  1. Calculate flow rate.

Before actually doing the calibration, you can get a rough estimate of how much you need to open your broadcaster and how fast you need to drive your ATV. With the ATV stationary, run the known amount of seed through (in our example, 0.312 lbs or 141.8 g), and time how long it takes to flow out.

For example, we opened our broadcaster ¼ of the way (different broadcasters may have different settings and may be more precise than others) and we timed 10 seconds for 0.312 lbs or 141.8 g of seed to flow out. Now, if we do the math we can find out how fast we need to drive the ATV to ensure we cover our calibration area with seed.

We get 10.8 km/hr. On some broadcasters it might be hard to see while operating and when the hopper is full where the settings correspond to ¼ opened. Mark somewhere on the broadcaster opening mechanism so that you can see while operating the broadcaster where ¼ open is.

  1. Test in the field.

Measure your calibration distance by placing flags 30 m apart in the field. Close the opening of your broadcaster and dump seed in from one of the ziploc bags. Start a few feet behind the first flag. Give yourself enough distance to get up to speed and then once you get to the first flag open the broadcaster to the appropriate setting (in this example ¼ opened).

  1. Adjust

After your first calibration run adjust your speed or broadcaster if needed. If you run out of seed too early, speed up or close your broadcaster slightly. If you run out after the 30 m, do the opposite.

  1. Multispecies mix tips!

Be mindful that some multi species mixes, especially if the seeds are shaped very differently, or have different densities, may separate out when you are broadcasting them in the field. Calibration is a good time to test distribution and whether they separate in the hopper significantly or not.

Useful resource:

By Jonathan Bent, Lead Field Research Associate with Perennia Food and Agriculture Corporation