Target Seed Depth to Access Moisture for Optimal Emergence

In many parts of the prairies, the spring of 2019 saw fields that were either dry, or drier, with rains first falling in mid-June or later. In the dry areas, it was easy to see who got the seed into sufficient moisture to establish their crop and who had not. Unfortunately, many operators had not. In all too many cases, in mid-September, the crops were not yet mature and were still vulnerable to being damaged by frost.

When moisture is accessible within the maximum allowable seeding depth of the seed, getting enough moist soil over top of the seed is imperative for successful emergence. This is made easier of course, if there is a rainfall immediately after seeding. Getting sufficient moist soil over top of the seed for achieving establishment without spring rainfall requires that the operator pay attention to the varying moisture conditions throughout the fields and adjusts the seeding depth accordingly. Seeding depth is most critical with the small seeds, with canola being the crop of primary importance given the acres that are seeded each year.
Where sufficient moisture was available at depths that allowed for establishment this past spring, adequate seed depth was not achieved for various reasons:
  1. Some farmers have come to expect rainfall after seeding as this has been the trend since the droughts of 2001 and 2002 so they selected a shallow seeding depth;
  2. Some farmers have made it a hard and fast “rule” not to seed deep regardless of the conditions. For example, not to seed canola more than 1" deep because in their experience, more often than not, seeding shallow has produced better results for them than seeding deeper, especially with canola;
  3. Many farmers now operate independent opener drills and changing the seeding depth on every opener can be very time consuming making it seem impractical to change the seeding depth within a field;
  4. With some of the dual-knife drills, going deeper promotes faster seedbed drying out than going shallower because the fertilizer knife creates larger soil lumps;
  5. Some drills are simply too light to penetrate into hard soil so they tend to go shallower on the hilltops where the moisture is usually located further down.
Another issue is that often farmers were able to successfully deposit the seed into the moisture; however, before the seed could absorb water and break the seed coat, the moisture had disappeared. In other cases, the seed coat was broken, but there was not sufficient moisture to keep the seedling alive.
Seeding fields that have variable topography at one depth will obviously work if rainfall occurs shortly after seeding; however, in years when there is no rainfall for an extended period of time before seeding, the moisture will be located deeper on the hilltops and upper mid slopes than on the lower mid slopes and the low areas. Whenever the moisture level varies greatly from the tops of the hills to the low areas, it is often impossible to get one seeding depth that will work for both areas, unless rainfall occurs shortly after seeding. Therefore, it is recommended that the fields be broken into zones and the seeding depth be adjusted for each of the topographical zones.
Benefits of the 3320 PHD™ 

The 3320 PHD Quick Depth Adjust provides its owners with the best chance to access sufficient moisture for excellent emergence in dry conditions such as the conditions that were witnessed in 2019.
3320 PHD Quick Depth Adjust
The Quick Depth Adjust feature allows the operator to set the depth efficiently…taking only minutes instead of the greatest portion of an hour while, at the same time, eliminating crawling on hands and knees, smacking heads or skinning knuckles and staying clean throughout the process. The QDA was a beneficial option to have in the success of establishing a crop 2019.
The QDA is a heavier and more robust drill than the competition; the QDA was designed to penetrate to the seed depth required in the harder, drier soil conditions that were present in 2019. The 3320 successfully gets into the moisture vs riding up and placing the seed in the dry soil.
The 3320 packs directly on the seed (not on the fertilizer band) to improve seed to soil contact and seal in the moisture, a key for seeding in dry conditions. The V-packer wheel option on the 3320 further proved to be the best wheel in these moisture challenged fields. One of the characteristics of many of the independent opener drills is that as the soil gets drier and harder more of the hydraulic pressure is used to try to keep the opener or openers in the soil. This results in the packing pressure being reduced where it is needed the most; on the eroded, dry hilltops.
The Bourgault PackMaster™ option maintains a uniform packing pressure and assists in keeping the opener at the specified seeding depth, regardless of how hard the soil is, which can result in better emergence in dry years.
Successful results have been reported by operators who deposited their seeds in moisture that was located well below the soil surface. In 2019, some operators seeded canola up to 2" deep in sandy, light textured soils and obtained good emergence shortly after seeding; whereas, those who stuck to the “no deeper than on inch” rule waited for 5 weeks for most of their canola to emerge.
Observations:
Seeding Depth Trial - 2019
Coincidentally, the Bourgault Agronomy Team conducted a study where canola was seeded at different times throughout the spring and at two different depths. The results indicated that placing the seed at 1½" deep to get sufficient moist soil overtop of the seed to achieve emergence in dry conditions provided better results than seeding at ¾" deep. The result was a more even emergence at a deeper depth where the moisture was present in the seed row, equating to quicker and more even flowering and earlier maturity. The photo is from the Agronomy Team’s study.
The photo was taken on August 8th when the canola was coming out of bloom. As you can visibly see, the May 7, 12 and 28 plots that were seeded at 1-½" deep are all more advanced than the plots seeded at ¾" deep. The maturity of the June 7th plot is similar for both depths as rain fell shortly after on June the 14th.
If rainfall occurs shortly after seeding, using one seeding depth for fields with variable topography will clearly work. It can also work if the moisture is right near the soil surface at the time of seeding. However, if there is an extended period without rainfall before seeding and an extended period without rainfall after seeding, as Western Canadian farmers witnessed in the spring of 2019, emergence results were often poor with the hills and upper mid-slopes not emerging until late spring.
With so many variables in play, how a seeding season will play out is impossible to predict. However, regardless of anything else, a seed requires moisture in order to germinate. Depositing the seed into sufficient moisture at the time of seeding is the only way to get even emergence in a dry spring. Being able to easily and quickly adjust the depth with the 3320 QDA allows for adaptability in any seeding condition.
Conclusion:

Removing the hesitation to adjust depth because it takes too long or is too difficult allows the decision to be made purely on agronomic factors.
 
Bourgault - Designing Equipment Around Agronomy