Air Seeder Distribution Accuracy

Thankfully, these days most air-carts and seeders are delivered from the factory with accurate metering and distribution systems already in place. However, it’s a good idea to know a few of the basics about how air-based distribution systems work so that you can make a few quick checks and adjustments to ensure that you’re getting maximum results from your air-seeding equipment.

The basic process of air based seed distribution is as follows:

Seed and fertilizer are metered out at a central point based on ground speed and the desired application rate.
High velocity air from a central fan moves the metered product from the air cart through a series of splitting and dividing stages. The aim is to evenly distribute the product across the machine’s width and provide each row with an equally divided rate of product.

The equal division of seed and fertilizer across most machines relies on equal amounts of air travelling through each section of the system after each subsequent division. The most important concept that you need to understand about your air seeding system is that air and seed will tend to flow through your machine favouring the path of least resistance.
To demonstrate the factors which can influence the accuracy of seed distribution by way of example, imagine a 3″ diameter hose supplying an average rate of seed by high velocity air into a two way splitter or divider with two 1.5″ diameter hoses attached to the outlets.

Hose Length:

If one of the outlet hoses was significantly shorter than the other, you would find that more air and seed would be delivered through the shorter hose than the longer hose – this is because there is less resistance in the shorter hose.

Hose Bends & Direction Changes:

If both the outlet hoses were of equal length but one hose was running straight, and the other running with a few bends and direction changes – you would find that there is less resistance in the straight hose and it would deliver more air and seed than the ‘bending’ hose.

Hose Elevations:

If both outlet hoses were of equal length but one hose was running straight and lying horizontally (flat), and the other hose was turned to point vertically (upwards towards the sky). The elevation of the upturned hose creates greater resistance to the flow of air and seed which would cause more air and seed to be delivered through the horizontal (flat) outlet hose.

So, the secret to ensuring that you have even distribution of product across your air seeding machine is to equalize the resistance after each stage of the line splitting / dividing.

Take a few minutes to work through your air seeding system to check for equal resistance after each stage of dividing. Begin at the metering unit, progressively check each point of line division for equal hose lengths, direction changes / bends, and hose elevations.

Resistance equalization is most critical in the primary lines, and bears less of an impact with higher fan speed settings. However, many operators have seen dramatic accuracy improvements by simply shuffling a few hoses around and ensuring hose layout ‘symmetry’ across a machine – and the best thing is that it’s something you can do quickly while checking over your machine before this planting season.

Dave Scott

D-Cup Diffuser