Over the past ten years direct seeding has become a more common practice than ever before. The following graph outlines the transition that has taken place since 1990.
A number of agronomic factors need to be considered as to "What Works, What Doesn't" when direct seeding canola.
If canola is going to be part of your rotation in the coming year, consider pre-harvest weed control. Weed pressure in early spring will substantially reduce the crop's ability to establish itself quickly. Don't assume there will be time for a pre-burn-off of weeds before planting.
The source will affect the appropriate timing of application. Apply elemental sulphur at least the year before, to allow the bacterial oxidation process to occur for the nutrient to be plant available in the year of production. Research at Agriculture and Agri-Food Canada, Melfort, has shown that it may take longer than a year, depending on soil texture and environmental conditions. Don't assume that under direct seeding practices the increased moisture and carbon amounts will allow this process to move faster. The graph below (1998 Canola Production Centres) show sulphate sulphur becomes available to the plant in the year of application.
This is essential for optimal seed to soil contact. Proper spreading of residue will increase plant populations, and ensure even germination and maturity. The rule of thumb is to spread chaff and straw the width of the swath that has been cut.
Soil testing allows for a fertility benchmark towards a productive and healthy crop. Insight of the soil nutrient status, combined with proper moisture utilization, will maximize yield potential of a variety. Under cool and stressful soil conditions (soil borne diseases) proper fertilization of a canola crop will help enhance early plant development. Don't assume the soil test done 2 or 3 years ago is still relevant. Available nutrients change dramatically from year to year, especially in the case of nitrogen and sulphur.
Seed early to take advantage of moisture availability. Snow trapping with stubble from the previous crop will increase moisture needed for germination. The work done at Canola Production Centres over the past 3 years indicate that early seeding will increase yields. These results concur with similar findings at Agriculture and Agri-food Canada's Scott Research Farm.
This practice takes advantage of cooler, moist growing conditions and assists in avoiding the drought and heat stress later, during crop development. Seeding early also takes advantage of longer day length and photosynthetic activity on a larger leaf surface area. This process should lead to increased nutrient uptake (moisture-dependent) and increased yield potential.
Balanced Fertility Package
Balancing nutrient levels between the major fertilizer elements is essential. The following is the approximate ratio:
| N | P2O5 | K2O | S |
| 5 | 2.4 | 4 | 1 |
If the goal is to produce one tonne per acre (44 bus/ac), the crop requires approximately 11 to 14 inches of water, 150 lbs. nitrogen, 78 lbs. phosphate, 125 lbs. potash and 31 lbs. sulphur.
Canola crops utilize anywhere from 20 to 90 percent of the applied fertilizer nitrogen, depending on soil type, moisture conditions, and nutrient balance.
The amount of fertilizer placed with the seed affects plant stand establishment. An understanding of seedbed utilization and row spacing is essential. Plant stands can be greatly reduced if high amounts of fertilizer are placed in a concentrated band near the seed.
A preferred plant stand, to achieve a productive canola crop should range between a minimum of 60 plants to 120 plants /metre2. The following chart outlines seeding rates and relative plants per square foot.
|
Seeding Rates - Seeds per Unit Area |
||
|
Rates: lbs/ac |
B. rapa - Sq. Foot |
B. napus - Sq. Foot |
|
2 |
9 |
5 |
|
3 |
13 |
8 |
|
4 |
17 |
11 |
|
5 |
22 |
13 |
|
6 |
26 |
16 |
|
7 |
31 |
19 |
|
8 |
35 |
21 |
|
9 |
39 |
24 |
|
10 |
44 |
26 |
Over a four-year study at Canola Production Centres in Saskatchewan, dramatically fewer plants emerged as nitrogen rates increased, depending on the opener used and its relative spread pattern.
Note: Broadcast treatment had nitrogen applied at 70 lbs/ac (actual).
When high rates of seed placed nitrogen are applied, there are two common occurrences:
Producers should realize that greater row spacing results in more concentrated fertilizer bands within the seed row.
The Canola Production Centre project indicates that urea nitrogen can be seed-placed with canola up to 70 lbs/acre of actual nitrogen (152 lbs/ac of 46-0-0) based on 8-inch row spacing. Keep in mind the amount of available moisture at the time of seeding. However, these guidelines need to be altered under some conditions. If the row spacing is greater than 8 inches, the row width utilization (R.W.U.) will be less, and therefore the actual amount of seed-placed nitrogen would be higher. If the row spacing between the openers is less than 8 inches, the R.W.U will be greater, and therefore the amount of seed-placed nitrogen would be lower. The graph below indicates how altering the row spacing from six, eight and twelve inches dramatically effects the R.W.U with each individual opener.
As the R.W.U. decreases with the different openers, a dramatic reduction in plant emergence may occur. This may cause an increase in weed pressure and a reduction in yield. With wider row spacing the amount of seed within the row is also increased, which causes greater in-row competition of canola plants.
Seed-to-soil-contact is enhanced if packing is done directly behind the opener on the planter. This promotes quicker seed germination, better moisture use efficiency, and even plant stands.
Seeding speed has a dramatic effect on proper seed placement. When speeds are above 6 mph, seed placement within the desired ¾" to 1" depth is difficult to achieve. Slowing down allows the planter to more precisely position seed. Moisture loss will be decreased because of less disturbance of the soil.
Recent research conducted at the Agriculture and Agri-Food Canada research station at Lacombe, Alta., and at Canola Production Centres, has shown that early weed removal in crop has resulted in yield advantages. The graph below illustrates the yield differences, at CPC's, between 1 to 3 leaf stage and 4 to 6 leaf stage of the canola crop relative to seeding dates.
It is important to understand the agronomic factors that are vital to success when direct seeding canola. By soil testing and planning, a producer can take precautionary measures to control weeds and increase plant available nutrients. Residue management and early seeding help to maximize use of soil moisture and ensure even maturity of plant populations. Proper use and management of fertilizers, appropriate seeding speed, adequate opener spread width/row spacing, and careful weed management are other important practices to maximize yield and quality when direct seeding.
The guidelines presented show "What Works" when direct seeding canola. "What Doesn't Work" is not gathering all the information available to make wise agronomic decisions when direct seeding. By following the guidelines presented, direct seeding should prove to be a success, from both an agronomic and economic perspective.
Jim Bessel is the Regional Manager and Senior Agronomist, Eastern Prairie Region, working with the Canola Council of Canada.