Adjusting Seeding Rates

In order to seed the recommended Pure Live Seed (PLS) seeding rate, the bulk rate of seeding needs to be determined. This is the rate at which the drill will be set. This rate will always be greater than the pure live seed rate. The formula to calculate the bulk seeding rate is:

Pounds bulk seeding rate per acre = pounds PLS recommended rate per acre percent / percent PLS

An example of how to use this formula is listed below. The NRCS recommended seeding rate for 'Hycrest' crested wheatgrass is 5 pounds PLS per acre. The PLS is calculated to be 80.0 percent. The bulk rate needed to seed the recommended PLS rate is determined by:

Pounds bulk seeding rate per acre = 5 pounds PLS recommended rate per acre / percent PLS

Bulk seeding rate per acre = 6.25 pounds

Based on these calculations, the drill box setting on the planting drill would be as close to 6.25 pounds per acre as the model of drill will allow.

The following chart can be used to convert any Lot of Seed to the bulk equivalent based on purity and germination:

To Use the Chart

1. Locate the percent purity and percent germination from the seed lot on lines A and B.
2. Lay a straight edge between these two points.
3. The point of intersection with line C is the conversion factor for this lot of seed.
4. Example: Purity 95 percent - line A, Germination 35 percent - line B
5. Conversion factor = 3.0 - line C
6. It will take 3 pounds of this seed lot to equal 1 pound pure live seed (PLS).
7. If the PLS seeding rate is 5 pounds/acre, then 5 x 3 = 15 pounds/acre would be the bulk seeding rate for this seed lot.

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Last Modified: 07/05/2007