Selecting the right opener and packer combination is a challenge for any direct seeder, whether they have a brand new air drill or not. Mess up on one component, and the other isn't likely to work very well either. When retrofitting an air seeder, there are a few more factors to take into consideration than when equipping an air drill. An understanding of the relationships between openers, packers and the soil, will ensure success in retrofitting an air seeder.
Crop residue management during the harvest before that first season of direct seeding is the first step in any successful direct seeding system. PAMI recommends straw be spread over 60 - 70% of the width of the cut while the chaff should be spread over 80% of the cut width. The ideal machine for spreading residue is the combine. However, a set of harrows will move around the straw. Once the chaff hits the ground, though, nothing can move it.
The ability of the seeding implement to clear residue must be considered during harvest. If the stubble is too tall or too much is lying on the ground, depending on the opener, there could be problems next spring.
The general rule of thumb is that stubble height should not exceed the shank spacing of the seeding implement. The stubble can be up to 1.5 x the shank spacing if the opener is a narrow knife or spoon. To prevent hair pinning with a disc opener, it's better to have tall stubble than to have a bunch of straw lying on the ground.
In terms of row spacing, research done by Dr. Brian McConkey, AAFC, Swift Current, indicates that that in the Brown and Dark Brown Soil Zones, a spacing of 10 inches (25 cm) or less is preferred because in drier areas, a wider row spacing has resulted in reduced yields. In the Black and Gray Soil Zones, any row spacing will work. In these two soil zones, the wider row spacing enhances residue clearance and cuts down on the number of costly openers.
On-row packing is essential in direct seeding. The purpose of a packer is to give the advantage to the crop seed over the weed seed by ensuring good seed-to-soil contact for the crop, leaving the weed seed stranded in loose soil. A coil packer has no place in a direct seeding system as both crop seeds and weed seeds are packed randomly.
On occasion, we're asked if packing after seeding is really necessary. The answer is YES! One of the most recent studies on packing was done by PAMI, AAFC and the Sask. Wheat Pool. A variety of packing pressures were applied to 3 different crops on 3 different soil types. As in previous studies, this one concluded that minimal packing provides higher emergence rates than no packing at all. For more information on packing, visit the PAMI booth and ask for their Research Update #749 - Does Soil Packing Matter?
One of the most important differences between an air drill and an air seeder is the amount of packing force each can exert. An air drill exerts a significantly greater force per wheel than an air seeder. In dry seeding conditions, crop emergence may be better in the fields seeded by the drill. The difference in packing pressures may also influence your choice of opener.
Packers come in a variety of sizes and shapes. The general rule of thumb is to match the width of the packer with that of the opener. A packer that is narrower than the opener will not pack all the seeds evenly. One that is wider than the opener will also pack weed seeds alongside the seed row or ride on the sides of the opener trench and not pack the seeds in the bottom of the seed row.
To ensure maximum separation between the seed and the fertilizer, centre a round or steel V shaped packer over the fertilizer row. This can push the seed off to the side by as much as another ½ inch (1.5 cm) away from the fertilizer. If the packer is centred over the seed row, the seed shelf may actually be crushed, pushing the seed onto the fertilizer.
Again, centre a round or V shaped packer over the fertilizer row. This will create a sideway pushing of the seeds away from the fertilizer. Speed is critical in maintaining the integrity of a paired row opener. Between 4.0 and 4.5 mph is the maximum travelling speed when using a paired row opener to prevent seeds from blowing off their shelves into the fertilizer row. The seeds that remain on the shelves will be more firmly packed than those in the bottom of the fertilizer trench resulting in uneven emergence. Flat packers are not recommended for use with a paired row opener as they may cause the seed shelf to crumble. Double shoot openers that place the seed and the fertilizer at the same depth don't go as deep into the soil as most other openers and the vertical face allows the soil flow around in behind the opener. As a result, these openers require less packing pressure and have less draft than many other double shoot openers.
A single shoot opener such as a knife or spoon is well suited for use on an air seeder. The disadvantage to a narrow single shoot opener is the limit to the amount of N fertilizer that can be seed-placed. Single shoot openers and flexible pneumatic and semi pneumatic packers with a scraper are especially well suited to clay and heavy clay soils as sticky soil will peal off the flat surface of the packer. It's very important that packer width match opener width.
High disturbance direct seeding is achieved when using a sweep or shovel. Following the seeding operation, not much crop residue is left on the soil surface and there is greater soil moisture loss as compared to a narrower opener. The advantage to seeding with a sweep is that it allows for greater amounts of seed-placed N fertilizer.
As with every other opener used for direct seeding, sweeps require on-row packers but once again the packers must be the width of your seed row. Even with the use of a 16" sweep, the seed row width may be only 5 to 6 inches. Uneven packing and ultimately, uneven emergence may result if the rear shanks are throwing soil over the seed rows created by the front shanks.
If swathing is a necessary operation, a paired row opener is thought to have an advantage over a single side band. One spring, the SSCA staff took 2 Flexicoil openers, one a paired row, the other a single side band, and attached them to a Flexicoil 5000 drill. When the cereal crop emerged, it was found that, at best, the paired row opener created a seed row one inch wider than the single side band. The gain of an extra inch in seed row width must be weighed against the extra care and attention that must be paid to a paired row opener. While there are now some paired row openers on the market that have wider separation, but this is offset with greater soil disturbance.
The bottom line is there is no perfect opener. An opener's performance is based on the prevailing soil and climatic conditions. What works on one soil type may not work so well on another.
Before purchasing an opener or opener-packer combination, talk to other producers who are using that system on a similar soil type. The SCA has available the Farmers Helping Farmers Directory, a database of farmers willing to talk to other farmers about the equipment they are using or have used. It's a great way to get unbiased information before any purchases are made.
Moving from one seeding system to another certainly has its challenges. Understanding how the equipment works together in the soil is a big move towards overcoming those challenges. Do what you can to ensure each seed is healthy when it pops out of the ground. The rest is up to Mother Nature.