Achieving a uniform plant stand begins with choosing the right seeding depth, adjusting packing pressure for soil conditions, and understanding how seed size, equipment, and environmental factors influence early plant development.
Whether working with small-seeded crops like canola and forages or larger-seeded crops such as corn and soybeans, consistent emergence lays the foundation for strong crop establishment and yield potential.
Small-Seeded Crops: Getting Seeding Depth Right
With smaller seeded crops like canola and alfalfa, it’s best to start with a shallow seeding depth.
- Canola: ½–1 inch
- Forages: ¼–½ inch
“As your seed goes deeper into the ground, the seeding rate should be increased to make up for the plants not reaching the soil surface,” said Justine Cornelsen, BrettYoung’s Agronomic and Regulatory Services Manager.
Packing Pressure Matters
Packing pressure must be adjusted for soil conditions:
- Dry soils: require firm packing for seed-to-soil contact
- Wet soils: require lighter packing to minimize soil crusting
“With a dry spring and dry soils, the seed needs to pull water from surrounding soil particles to germinate,” said Cornelsen. “In wet soils, packing pressure can be less to minimize the potential of the soil crusting.”
Opener style and fertilizer placement may also affect how firm the seedbed is.
Seed-Placed Fertilizer Guidelines
Seed-placed fertilizer can compromise uniform emergence if applied incorrectly.
- Canola: 15–20 lb/acre of phosphorus can be safely seed-placed
- Forages: 10–15 lb/acre
Remaining fertilizer for small-seed crops is best placed in a side band.
“Seeding slow allows for uniform shallow seeding,” said Cornelsen. “Seeding speed should be set based on the drill’s performance to achieve uniform seed depth.”
Corn and Soybeans: Adjusting Depth for Larger Seed Size
Larger seeded crops can be placed deeper and still achieve uniform stands.
- Soybeans: ¾–1¾ inches
- Corn: 1¾–2¼ inches
Corn requires deeper seeding so seminal roots develop below the soil surface for proper anchoring.
Equipment Considerations
Corn and soybeans can be seeded with a drill, but a row planter improves accuracy and minimizes skips or doubles.
“Corn plants are very sensitive to their surroundings,” Cornelsen noted. “Seed double-ups can cause weaker plants within the crop canopy, which hurts uniformity in the end.”
Keep the Field Weed-Free
The critical weed-free period must remain weed-free to avoid yield loss. Row-planted crops take longer to canopy, making timely weed control essential.
Uniform crop canopies support:
- Easier in-crop herbicide decisions
- Reduced herbicide injury
- More predictable emergence
Weather is the Wild Card
Weather always influences emergence, and growers can only plan around it.
Soil Temperature Drives Emergence
- Soybeans:
- Emerge in approximately 4 days at soil temps above 14°C
- May take up to a month in cold soil
- Canola:
- Germinates at 2°C
- Emerges fastest above 10°C
“Seed that germinates but is slow to emerge becomes susceptible to seedling diseases and runs the risk of using up energy reserves,” said Cornelsen. “Which leaves it stranded.”
Crop Rotation and Disease Pressure
Rotation impacts seedling disease risk. “Crop rotations that are heavy on a specific crop type influence the pathogens within the soil,” Cornelsen explained. “The more often a crop is grown in that soil, the more likely the seedling pathogens it’s susceptible to will be present.”
Slow emergence increases vulnerability as seed treatments begin to wear off.
Final Thoughts
Regardless of seed size, achieving a uniform plant stand is essential for setting yield potential early. Plant establishment locks in much of a crop’s productive capacity — the remainder of the season is spent preserving it. And, as always, a little rain helps.
FAQ
What is the optimal seeding depth for small seeded crops like canola and forages?
For canola, the optimal seeding depth is about ½ to 1 inch deep. Most forage crops should be seeded even shallower, at ¼ to ½ inch.
How should packing pressure be adjusted based on soil conditions when seeding?
Packing pressure should be increased with dry soils to ensure firm seed-to-soil contact and should be less in wet soils to minimize soil crusting.
What are the safe rates for seed-placed phosphorus fertilizer in canola and forage crops?
For canola, 15 to 20 pounds per acre of phosphorus can be safely placed with the seed. For forages, 10 to 15 pounds per acre is recommended.
How do seeding depth guidelines differ for corn and soybeans compared to smaller seeded crops?
Corn and soybeans can be planted deeper in the soil, with soybeans at ¾ to 1 ¾ inches deep and corn at 1 ¾ to 2 ¼ inches as they can still achieve uniform plant stands at these depths.
Why is it important to keep corn and soybean fields weed-free during the critical period?
Keeping the fields weed-free during the critical period prevents yield loss and helps achieve uniform plant emergence.
How does soil temperature impact seed emergence for soybeans and canola?
Soybeans can emerge in as little as four days if seeded into soil above 14°C but can take up to a month in cold soils. Canola can germinate at 2°C but emerges faster above 10°C.
What role does crop rotation play in seedling disease pressure?
Crop rotations with heavy emphasis on a specific crop type increase the likelihood of seedling pathogens being present in the soil which can increase disease pressure.
