Recommended soybean seeding rate

Adjusting for iron chlorosis Soybean seeding rates may need to be increased over the standard recommendation of 150,000 seeds per acre in high calcareous soils where “iron chlorosis” or lime-induced chlorosis is a possibility. Seed density within the row affects how well a soybean variety tolerates an alkaline soil and increased rates can even benefit tolerant varieties. Use a planting rate of 12 viable seeds per foot, regardless of row spacing. This seeding density is excessive for most varieties grown in less alkaline soils, but the in-row density of drilled soybeans typically isn’t adequate for alkaline soils. Lime induced chlorosis is common in calcareous soil and in certain soils in Nebraska’s Platte, Elkhorn and Republican River valleys. In addition to increasing plant density, management for lime induced chlorosis requires selecting tolerant varieties, applying materials such as iron chelate with the seed and using foliar application of iron. Charles Wortmann Extension Nutrient Management Specialist

Using an optimum seeding rate without overplanting is also important to the operation=s bottom line. Much of the seed planted in Nebraska is now biotech or treated, thus seed costs have increased and now represent costs for seed and some pest management. Average soybean seed costs a decade ago were $15.50 per acre for seed with inoculant, while now a more typical cost would be $35 for treated seed (including inoculant). At one time overplanting by 50,000 seeds per acre may've seemed like inexpensive stand insurance, while now it represents a major added cost.

Results from numerous seeding rate experiments across Nebraska over the years have shown the same thing: seeding about 150,000 viable seed per acre will optimize yield. (See box for exception on high calcareous soils.) This rate is the same in both dryland and irrigated production and for most varieties. Nebraska research also indicates that this is the best rate regardless of row spacing. Research on normal, very large, and very small seeded soybean varieties found no difference in soybean responses to seeding rates between 10- and 30-inch rows. With normal plant losses, this rate will result in 100,000 or more harvestable plants per acre. Seeding rates over 150,000 seeds per acre will neither increase nor decrease yield if plant lodging doesn't occur.

This answer presumes that good seed-soil contact is possible with the narrow rows and optimum soil conditions exist. In narrow rows, yield response is best optimized in narrow rows when plants are more uniformly distributed in the row. If these considerations are not met, consider increasing the seeding rate by 10% to 20%.

Seeding rates may need to be higher when replanting or late planting soybeans. When determining soybean seed rate, be sure to base your decision on seeds per acre rather than pounds per acre. Seed weights vary considerably among varieties and among production seasons. This can affect seeding rates and final stands. Variations in seed size also can affect planter calibration. Once your planter is set up, check actual seed drop to insure you are getting what you had planned for. If you're planting 150,000 seeds per acre, a general guide to seeds per foot of row would be:

in a 36-inch row, approximately 10.3 seeds per foot of row;

in a 30-inch row, approximately 8.6 seeds per foot of row;

in a 20-inch row, approximately 5.7 seeds per foot of row;

in a 15-inch row, approximately 4.3 seeds per foot of row; and

in a 10-inch row, approximately 2.9 seeds per foot of row.