Soybeans can be planted at varying seeding rates because growers know that different rates within an acceptable range can be used without affecting yield potential. Seed of today's biotech varieties often cost more than $30 per 50 pounds. Thus, the seeding rate decision now has significant economic implications.

Information in the accompanying table can be used to determine how much a particular seeding rate will cost, and how much a change in seeding rate will affect cost.

For instance, if seed cost is $30 per 50 pounds, increasing seeding rate of a 3,000-seeds-per-pound variety from 120,000 to 160,000 seeds per acre will increase cost $8 per acre when 50 pounds are planted.

If there is no agronomic reason to use the higher seeding rate, the extra seed cost will reduce net return.

On the other hand, producers may decide that the extra cost is worth the peace of mind gained from planting on the higher end of the range to ensure an acceptable stand in a planting environment that is less than ideal.

Planting the same number of seeds per acre of comparably performing varieties with a different number of seeds per pound will affect cost.

For instance, planting 140,000 seeds of a variety with 3,000 seeds per pound will cost over $4.50 per acre more than planting the same number of seeds of a variety with 3,600 seeds per pound. If the two varieties are comparable in performance, then this higher cost will reduce net income.

Producers should use their prior seeding rate experience to make an economical seeding rate decision.


Larry G. Heatherly is a retired USDA-ARS research agronomist and current crop consultant. e-mail larryheatherly@bellsouth.net

Number of seeds per foot of row and cost per acre for soybean seed of varied size and cost planted at different seeding rates in five row spacings.
Row spacing — inches Cost/50 lb. of seed
Seed size Seeding rate 7 15 20 30 40 $15 $20 $25 $30
No./lb. seeds/acre lb./acre No. seed/ft. of row $/acre
2800 100,000 35.7 1.3 2.9 3.8 5.7 7.7 10.71 14.29 17.86 21.43
120,000 42.8 1.6 3.4 4.6 6.9 9.2 12.86 17.14 21.43 25.72
140,000 50.0 1.9 4.0 5.4 8.0 10.7 15.00 20.00 25.00 30.00
160,000 57.1 2.1 4.6 6.1 9.2 12.2 17.14 22.86 28.57 34.28
180,000 64.3 2.4 5.2 6.9 10.3 13.8 19.29 25.71 32.14 38.57
200,000 71.4 2.7 5.7 7.6 11.5 15.3 21.43 28.57 35.71 42.85
3000 100,000 33.3 1.3 2.9 3.8 5.7 7.7 10.00 13.33 16.67 20.00
120,000 40.0 1.6 3.4 4.6 6.9 9.2 12.00 16.00 20.00 24.00
140,000 46.7 1.9 4.0 5.4 8.0 10.7 14.00 18.67 23.33 28.00
160,000 53.3 2.1 4.6 6.1 9.2 12.2 16.00 21.33 26.67 32.00
180,000 60.0 2.4 5.2 6.9 10.3 13.8 18.00 24.00 30.00 36.00
200,000 66.7 2.7 5.7 7.6 11.5 15.3 20.00 26.67 33.33 40.00
3200 100,000 31.2 1.3 2.9 3.8 5.7 7.7 9.38 12.50 15.63 18.76
120,000 37.5 1.6 3.4 4.6 6.9 9.2 11.25 15.00 18.75 22.50
140,000 43.8 1.9 4.0 5.4 8.0 10.7 13.13 17.50 21.88 26.25
160,000 50.0 2.1 4.6 6.1 9.2 12.2 15.00 20.00 25.00 30.00
180,000 56.2 2.4 5.2 6.9 10.3 13.8 16.88 22.50 28.13 33.76
200,000 62.5 2.7 5.7 7.6 11.5 15.3 18.75 25.00 31.25 37.50
3400 100,000 29.4 1.3 2.9 3.8 5.7 7.7 8.82 11.76 14.71 17.66
120,000 35.3 1.6 3.4 4.6 6.9 9.2 10.59 14.12 17.65 21.18
140,000 41.2 1.9 4.0 5.4 8.0 10.7 12.35 16.47 20.59 24.71
160,000 47.0 2.1 4.6 6.1 9.2 12.2 14.12 18.82 23.53 28.24
180,000 52.9 2.4 5.2 6.9 10.3 13.8 15.88 21.18 26.47 31.77
200,000 58.8 2.7 5.7 7.6 11.5 15.3 17.65 23.53 29.41 35.28
3600 100,000 27.8 1.3 2.9 3.8 5.7 7.7 8.33 11.11 13.89 16.66
120,000 33.3 1.6 3.4 4.6 6.9 9.2 10.00 13.33 16.67 20.00
140,000 38.9 1.9 4.0 5.4 8.0 10.7 11.67 15.56 19.44 23.33
160,000 44.4 2.1 4.6 6.1 9.2 12.2 13.33 17.78 22.22 26.67
180,000 50.0 2.4 5.2 6.9 10.3 13.8 15.00 20.00 25.00 30.00
200,000 55.6 2.7 5.7 7.6 11.5 15.3 16.67 22.22 27.78 33.33