Air Seeder Fan Speed – How fast is too fast?
How do you set your air seeder fan speed?
Chances are, you turn it up fast enough to make sure that the product gets to each opener without plugging the distribution hoses. If you’re a good operator, you’ll probably be concerned to make sure that it’s not running too fast.
There are two obvious reasons to make sure that your fan isn’t running too slow:- Prevent hose plugging – if you’ve ever had to unblock plugged hoses you’ll know how time consuming this is and how frustrating it is to leave a big pile of seed and fertilizer dumped onto the ground in your field.
- Ensure distribution uniformity – accurate distribution of product across your machine is vital to consistent germination.
- Seed damage – cracked or split seeds may not successfully germinate even if accurately seeded.
- Seed bounce – seeds that are ‘blown’ into the trench by excessive air-speed are likely to bounce around and end up at inconsistent depths; resulting in inconsistent germination.
“Fan Speed: Fan speed has a significant effect on distribution uniformity. In order for material to remain suspended in the air flow, air velocities of 1200 to 1800 rpm are required. As the amount of material in the air stream increases, the pressure or resistance to flow increases. To maintain this balance the fan speed has to be properly selected and maintained. Any variations in this speed can result in reduced uniformity. Velocities that are too high can also result in seed damage. This is a concern with seeds that split easily, such as canola and peas. At very high application rates, fan speed or air velocities may be the limiting factor. At air velocities below 1200 rpm the material may not remain in suspension and result in plugging of the distribution system. In the past, not enough emphasis has been placed on fan speed recommendations. This variable is as important as the meter setting.”
Now, there seems to be some debate lately about just how much damage (or cracking) is caused to seeds when distributed through air seeders – particularly with higher fan speeds.
Here’s a recent article written about a study commissioned by the Canola Council of Canada because some of their field trial work showed up to 30 percent seed damage (loss of germination) with air seeders. However, the results of a study conducted by PAMI revealed very little damage to the seed even when a number of seed types were tested at a variety of speeds.
Similarly, damage reported to chickpea seed was as low as 3 percent in from tests conducted with late model Case IH air seeders – read the test results here.
So it seems, based on these recent tests, that most modern Air-Seeders are very well designed and cause insignificant amounts of damage to most seeds.
Does this mean that none of your seeds will ever be damaged by running them through your air seeder? No, of course you’ll still need to be conscious of seed damage with certain types of seed. But, it does ask you revisit your approach to weighing up the factors that may lead to reduced germination and poor plant stand.Here’s my spin on what all of this means…
…You’ve got more to lose in poor performance by running your air seeder fan too slow than by running too fast…
The fact is that you only need the ‘air’ in the ‘air-seeder’ system to divide and move the product from the central fill point at the cart out to each opener across the machine. Once it gets there, high velocity air is the last thing that you want when trying to consistently place the seed at the optimum depth for maximum germination.
This is exactly why the D-Cup Diffuser was developed. They allow you to turn up your air seeder fan and use the cyclone effect to remove 100% of the air from the line just above each point of seeding – giving you the accuracy of a gravity drop system with the efficiency of an air seeder.
Order a few sample D-Cup Diffusers, fit ‘em to your machine, turn up your fan, see for yourself that they remove 100% of the air from the line.
Dave Scott
D-Cup Diffuser Co.