Colorado Plant Materials Program Resources, Vol. I, March 2011
“Seed Calculation Formulas”
The purpose of this document is to provide a quick and easy reference for how to calculate seeds per
square foot and number of plants per acre. This is a reference document to show the calculations, not a
technical note, job sheet, or standard.
How to calculate seeds per square foot from pounds of pure live seed:
Given: 170,000 clean seeds/ 1 pound of Eriogonum heracleoides Nutt.
If that pound were evenly spread out over one acre (43,560 ft.2)…
170,000 seeds/lb÷43,560 ft.2=3.9 or ≈ …. 4 seeds per square foot
How to compute pure live seed: Calculated by the % germination and
% purity as verified by a seed-testing laboratory using the 400-seed
germination test.
Whorled buckwheat (Eriogonum
heracleoides) seed. Photo by Derek Tilley.
% Purity X % Germination = PLS
100
From the seed tag below for Indian ricegrass:
66% x 97% = 64 % PLS
100
If, for example, the customer wants Indian ricegrass to make up 25% of the seeding mix, with a
recommended drill seeding rate of 4 lbs./acre
PLS they will need 1PLS lb. of Indian ricegrass.
How many bulk pounds will be required?
# of PLS Lbs needed = Bulk Lbs.
percent PLS
1/ .64 = 1.5 Bulk Pounds
USDA NRCS an Equal Opportunity Employer and Provider
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References:
1. Colorado Plant Materials Tech Note 59 (revised 2002)
2. “Why Pure Live Seed” Manhattan Plant Materials Center 2010
3. “A Field Guide for Collecting Native Seeds in Nevada”, University of Nevada Reno Cooperative
Extension 2003.
4.
USDA NRCS an Equal Opportunity Employer and Provide
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