Vol.2, No. 2, l994
1. The linear length of row needed to drill 35 seeds/ft2 is calculated by dividing 144 square inches in a ft2 by the drill row width For example: Using a drill with 7 inch row width, dividing 144 by 7 = 20.6 inches of row length for 35 seeds at 90% or greater germination. The following chart can be used as a guide to determine the optimum seeding rate based on a germination of 90% or higher.
Length of row Seeds/row foot needed* Row width needed for 1 ft2 35 seeds 30 seeds (inches) (inches) per ft2 per ft2 4 36.0 12 10 6 24.0 18 15 7 20.6 20 17 8 18.0 23 20 10 14.4 29 25
* In fields where yields are not expected to be quite as high, establishing from 25-30 plants/ft2 will require only 30 seeds/ft2. If planting time is delayed, increase seeding rates by 2-3 seeds/ft2 (1-2 seeds/row foot) for every two week delay beyond the optimum planting date.
2. The following chart can be used to calculate pounds per acre needed if the seed size is known.
Seeds per Seeds/square foot*. pound 35 30 Lbs/acre . 10,000 150 131 12,000 127 109 14,000 109 93 16,000 95 82 18,000 85 73 20,000 76 65 .*Based on 90% or greater germination
If the number of seed per pound is not stated on the seed tag, you can determine as follows:
l. Weigh a 20 gram representative sample.
2. Count the number of seeds in the sample. (Do this at least 3 times.)
3. Multiply the number of seeds counted by a factor of 22.68. This equals seed per pound.
l. Determine the mumber of revolutions the drive wheel must turn to travel 50 feet.
a. Measure the distance around the drive wheel. Example = 60"
Inches traveled in 50 feet = 50 ft x 12 inches/foot = 600 inch distance.
Number of tire revolutions per 50 feet = 600 inch travel distance divided by 60 inches per tire revolution = 10 turns of the tire per 50 feet.
2. Determine the number of seeds needed for distance you will travel to calibrate for a 7 inch row width.. a. 50 feet of row x 20 seeds/foot of row = 1000 seeds. 3. Count out 1000 seeds of the seed lot to be planted and put the seed in a graduated tube such as a rain gauge of other guage or other clear tube and mark the level of 1000 seeds in the tube. 4. Set the drill on a rate expected to be close and turn the wheel the number of revolutions needed for 50 feet while catching the seed from one row. Pour the seed caught in the pre-calibrated tube for 1000 seeds and check the level. Repeat for each of the rows caught. 5. Change settings and repeat until the appropriate number of seeds is obtained (level marked on tube).
1. If germination is below 90%, then wheat seeding rates should be adjusted.
2. Calculate seeding rate adjustments for germination by dividing the desired seeding rate (seeds/ft2) or (lbs/acre) by the percent germination.
Examples: a. 35 seeds/ft2 divided by 85% germination = 41.2 seeds/ft2. b. 127 lbs/acre divided by 85% germination = 149.5 lbs/acre.