Planning canola seeding rates involves more than using what worked last year, or using what a neighbour uses. With canola seed at prices up to 11 dollars per pound and grain selling for 13 dollars a bushel, a miscalculation can be costly. Calculating seeding rates should be done on an individual basis and should be adjusted according to seed size and the risks associated with each producers seeding operation. The recommended target plant populations for canola are 80 to 100 plants per metre square. The other information producers need to calculate canola seeding rates with are: the thousand kernel weight (TKW) and the expect emergence rate.
The TKW is printed on the seed tags for each lot of canola seed and is expressed in grams. The range of hybrid canola seed can be from three to seven grams per TKW and is not specific to variety. Seed size is impacted by the environment and is specific to each lot of seed. When looking for seed sources this year be aware of seed size and adjust seeding rates accordingly. Table 1 shows the impact of seed size on potential seeding rates.
The expected emergence rate is the rate at which the canola you plant comes up as seedlings. In other words, if the emergence rate is 100 per cent then we would expect every seed we plant to come up. Canola Council of Canada has found that emergence rates with canola on average range from 40 to 60 per cent with an average of 50 per cent. This means that roughly half of the seed that is put in the ground will emerge under normal conditions. Factors that can affect the emergence rates include seeding depth, wind speed of airseeder, amount of seed placed fertilizer, and soil conditions such as temperature and moisture.
Increasing the seeding depth can reduce emergence rates. Seeding canola shallow at less than one inch is critical for faster and more uniform emergence. Another factor to consider is the airflow setting used with your airseeder. Higher airflow can cause the canola to crack as it hits various parts of the seeder as it moves through the hoses and manifolds. Not only can the air speed have an affect but the equipment can cause some cracking or damage to the seed as it passes through the seeding systems. Checking the seed as it comes out of the opener before you seed your field will allow you to make adjustments and give you the confidence that the seed is of sound quality going into the ground. You can check the seed by removing one or two hoses from the openers and placing a sock over the hose while you are setting your seeding depth. The sock will collect the seed and allow you to judge whether your equipment or airflow are causing any damage to the seed. Visual inspection of the seed should allow identification of cracking of the seed.
Another factor to consider is the amount of seed placed fertilizer. To figure out how much fertilizer you can put safely with the seed you need to calculate the seedbed utilization (SBU) for your seeder. SBU is the amount of seedbed over which the fertilizer has been spread. In other words it is a reflection of the relative concentration of the fertilizer in the seedrow. The calculation for SBU is width of spread coming out of the opener divided by the row spacing multiplied by 100. For example, if the opener spreads the seed and fertilizer over one inch and the row spacing is 12 inches the SBU would be 1/12 x 100 = 8.3 per cent. The wider the row spacing and the narrower the spread the more concentrated the fertilizer is with the seed and the lower the allowable limits. Applying fertilizer above the recommended safe rates can negatively affect plant stands which reduces the emergence rates.