The Evolution of Dual Shank Openers

A single shank was then used to place seed and fertilizer utilizing two air kits, aiming to create two separate bands. This helped reduce seed toxicity by placing seed on one side of the opener and fertilizer on the other side or below. However, mixing of the products could not be completely avoided. As fertilizer rates continue to rise and seeding conditions vary, the risk of fertilizer burn to the seed is unacceptable to many.

Dual shank openers were developed to improve separation of seed and fertilizer into distinct bands and reduce mixing between them. Fertilizer placement remains relatively close, but mixing is greatly reduced in most soil conditions. Understanding soil flow mechanics through this style of opener is important when setting and operating.

>> To eliminate the risk of fertilizer burn, MRB Fertilizer Applicators can be used.

SOIL FLOW OF A DUAL SHANK OPENER

The front shank typically applies fertilizer, while the second shank places seed. The seed shank also serves an important secondary purpose: moving soil on top of the fertilizer band applied by the front shank. This makes the seed shank act like a closing tine, greatly reducing mixing between fertilizer and seed. Mixing can still occur in heavy clay soils where the front shank disrupts seedbed integrity, preventing soil from fl owing back over the fertilizer and allowing seed to mix with fertilizer.

"Dual shank openers were developed to improve separation of seed and fertilizer into distinct bands and reduce mixing between them."

DEPTH CONTROL

There are two aspects of depth with a dual shank opener:

1. Depth in the soil profile is set by the front fertilizer shank. As this shank goes deeper, the second seed shank and packer wheel follow into the trench. The deeper the front shank goes, the deeper the trench becomes.
2. Depth of soil over the seed is set by the seed shank relative to the packer wheel. This determines how much soil flows back over the seed before the packer wheel rolls over the trench. The deeper the second shank is relative to the packer wheel, the more soil will flow back on top of the seed.

HOW TO MEASURE DEPTH WITH A DUAL SHANK OPENER

The most common way to measure depth with a single shank opener is to measure the depth of soil over the seed. Depth in the soil profile and soil over the seed move together, so going deeper in the soil profile also puts more soil over the seed, making this method logical.

With a dual shank opener, depth in the soil profile and soil over the seed can act independently. When you go deeper with the front fertilizer shank to find moisture, you increase depth in the soil profile. If only the fertilizer shank depth is adjusted, soil over the seed will be minimally affected.

>> Can we utilize the QDA (Quick Depth Adjust) option with a dual shank system? Yes. By adjusting the frame, the fertilizer shank depth changes, which affects depth in the soil profile.

WHY IS THIS STYLE OF OPENER BENEFICIAL?

• Reach moisture without burying the seed: In dry years, the saying “put it in dust and the bins will bust” means don’t chase moisture and hope for rain. With a single shank, chasing moisture often results in excessive dry soil over the seed. If significant rainfall occurs afterward, wet soil can bury the seed and cause emergence problems. With a dual shank, you can go deeper in the soil profile without necessarily adding more soil over the seed, reducing this risk.
• Decreased risk of overpacking: The packer wheel is centered between the fertilizer and seed shanks. Since the seed shank moves soil back over the fertilizer, the highest point contacting the packer wheel is the soil over the fertilizer, while still applying some pressure over the seed.
• Blackens the seed furrow: The front fertilizer shank acts like a tillage knife, similar to a mini strip-till system, creating more soil throw and a blacker seed furrow. This improves sunlight absorption and warms the seedbed, helping germination.
• Consistent seed depth: The front shank moves dry soil and residue out of the way, and seed depth is determined by the back shank relative to the fixed packer wheel, ensuring consistency.

CHALLENGES WITH A DUAL SHANK OPENER

• Residue management: Straw and residue flow around the front shank and can accumulate on the second shank, leaving “muskrat huts.” A good chopper and sharp blades improve residue management, and harrowing is often helpful.
• Moisture loss: The front shank disturbs more soil as it applies fertilizer, increasing the risk of moisture loss, which can affect germination in dry conditions.
• Compromised seedbed integrity: Heavy clay soils may not flow well around openers when very wet or dry. The front shank can create a large trench, preventing the seed shank from moving soil back over the fertilizer band and increasing the risk of seed falling into the fertilizer band, causing emergence issues.
• Fertilizer burn: With fertilizer placed 1.5” to the side and 0.75” down, high rates can damage germinating seeds. Factors affecting risk include:
  • Type of seed: Canola is more susceptible than cereals.
  • Soil type: Sandy soils have higher risk than clay soils.
  • Soil conditions: Low moisture and no rain after seeding increases risk.
  • Type of fertilizer: Urea poses higher risk than MAP.
  • Rate of fertilizer: Higher rates increase risk, with tipping points depending on the above factors.

The best way to reduce risk is to place high fertilizer rates farther from the seed. This can be done with PLDS and PLDX openers by moving the seed away from fertilizer in ½” increments or adjusting the fertilizer shank deeper relative to the seed.

To eliminate fertilizer burn risk, MRB fertilizer applicators can be added to create a TriMax configuration: seed in its own band, starter fertilizer in a side band, and bulk fertilizer in a mid-row band.

Although Bourgault offers a dual shank opener that works well in certain operations and soil types, a single shank opener with MRB fertilizer applicators may be better for some areas and fertilizer programs.

Bourgault has the openers and fertilizer applicators to suit your specific operation, helping you get your crop in, and out of, the ground efficiently and consistently.