Agronomy Library > Soil Conservation

What's the BEST Opener?
Author: Ron Heller, Reduced Tillage LINKAGES
Date Created: March 26, 2003
Last Reviewed: February 21, 2007

Direct-Seeding: More than Opener Design

It is quite difficult to discuss all the specifics of a direct seeding system in short columns like this, but I often get asked, “Which opener is best?” - Too much emphasis is placed on choosing an opener! As a reduced tillage agronomist, I am confident in the research and design testing that has gone into most of the direct-seeding technology in use today. For growers, opener choice often begins at ground level by deciding on the soil disturbance and field finish created by the seeding implement, along with consideration for a compatible fertility package. Numerous manufactures offer several variations at competitive pricing and a bit of field-testing will go a long ways. However, because an opener doesn’t just seed, a discussion from the standpoint of basic opener function may be helpful to indicate what “best” infers.

An important goal for direct seeding is to ensure the crop is favored over weeds. Undisturbed soil and mulched crop residue between the seed rows contribute to the success of direct seeding. Fewer weeds grow and less soil moisture is lost (narrow openers and wide row spacing optimize this). Minimal soil disturbance with precision-placed crop nutrients at the time of seeding is the key. There are important equipment issues and guidelines related to soil texture, crop type and fertilizer forms that I will not get into, rather I would point out four distinct designs that have become “standards”, found in both factory and farm-built direct seeding machines:

1)       Side-banding (SB) is the art of placing a concentrated fertilizer blend nearby, but safely separated from a row of seed. Sometimes this is accomplished with a single opener, while other implements rely on a combination of narrow knife openers, furrow closers, row packers and other attachments.
2)       Mid-row banding (MR) refers to the placement of nitrogen fertilizer between two adjacent seed rows. A separate opener, usually a disc coulter or narrow knife is used.
3)       Paired-row seeding (PR) combines the first two concepts. Typically, the opener is designed to place fertilizer deeper but between two matched rows of seed. Some machines use a grouping of openers.
4)   Wide-row (WR) generally applies to an opener design that distributes seed and fertilizer in a broad, high disturbance pattern. Various fabrications of spreader-tips and boots mingle or separate the seed and fertilizer in a range of width and depth.

As described here, most SB, MR, PR and WR designs depend on a uniform and balanced distribution. Air Seeding provides double-shoot delivery systems that place seed, fertilizer and other products in variable combinations and locations spread over a large area of machinery. Refining multi-shoot technology for specific conditions appears to be crucial in the satisfactory performance of the modern direct seeding machine. Some modification of these standards is possible with liquid fertilizer, lower nitrogen rates, or single-shoot delivery.

Direct seeding allows a range of row spacing wider than with traditional seeding methods. This means superior crop residue clearance and improved equipment and field efficiency. Many studies have shown that row spacing up to 30 cm (12 inches) does not significantly affect emergence or yield in direct-seeded crops, with attention to weed control and appropriate seedbed utilization (SBU). This refers to the spread and distribution of seed and fertilizer in each furrow across the seeder width. According to research, guidelines for SBU may differ by climatic zone, with soil quality and for each crop type.

The “best” openers merge all of the above points for one-pass low disturbance seeding, however many operators are satisfied with a simple two-pass method – low-disturbance angle-discs, shank points, knives, spoons, or modified hoes and sweeps to pre-band fertilizer ahead of seeding. Often the same implement is used for both operations. Caution is needed, with multi-pass high disturbance, because compromises to the seedbed integrity may occur (ie: pre-seed weed control, residue clearance, furrow closure, row-packing, etc.). The implement designs discussed herein will normally perform best the first time over a field. Direct seeding into pre-worked fields is not the same as into undisturbed stubble.

To summarize - The soil-engaging performance, residue clearance and fertilizer delivery of any direct-seeding machine is more than engineering. Selecting a design best suitable for a farm’s soil and climate will vary by location and a manager’s preference for lower or higher soil disturbance. Each design works best under specific conditions. All have limitations - not every machine will likely achieve the same results in the same field for the same crop every year. A farmer’s direct-seeding system must not only address soil texture, but also a fertility program, crop rotation, field finish, weed situations, and his harvesting needs. This may seem complex, but it is now being done successfully (and is a growing trend) for over 65% of the annually cropped acres in Alberta (2001 Canada Ag.Census). Operator skill and experience ultimately become the chief factors that determine which opener works well.

There really isn’t a “best” opener to advocate, but the points mentioined above boldly suggest that direct seeding works best with attention to specifics. A grower should be asking “Can I achieve these objectives with just any opener?”. Better or more openers are not needed, just more direct seeding! Consulting with experienced direct seeders, watching for a deal on good used equipment, or getting a few fields custom seeded are ways to get started. RTL administers a Farmer-to Farmer direct seeding network for information sharing. For novice direct seeders, here is a 4-step guideline to get the most out of any direct seeding machinery, regardless of the opener design: 

- Distribute the previous crop residue evenly (chop and spread straw, collect or spread chaff, bale, etc).
- Do a pre-seed weed burnoff with glyphosate herbicide (ie:Roundup @ ½ litre/acre).
- Understand SBU and fertility guidelines for the crops you grow (charts are available).
- Travel slowly (4-5 mph) and inspect the seed row often (check depth, separation, and closure).