Targeting Optimal Canola Plant Densities at Sowing
Getting canola establishment right the first time is critical to ensuring a strong return at the end of the season. While there are many factors impacting establishment, targeting the correct plant density for your growing region and paddock scenario is an important starting point. Seed size, germination percentage and field establishment should also be taken into consideration as they will determine the seeding rate that is required to reach the desired plant density.
Figure 1: The equation above can be used to calculate the seeding rate required to reach the desired plant density during planting.
Optimal plant densities can vary depending on whether an open-pollinated or hybrid variety is used, what the weed burden is in the paddock and on what the target yield for the paddock is. In high rainfall areas target sowing densities can range between 40-60 plants per m2 for open pollinated varieties and 30-40 plants per m2 for hybrid varieties.
While it may be tempting to reduce optimal plant densities when sowing hybrid varieties, caution should be exercised as having less plants per m2 can leave you susceptible to larger losses at the end of the season. Environmental factors such as insect, slug or mice damage can take out plants in the establishment phase which can reduce the number of plants and hence the yield potential of the crop. Having low densities can also reduce yields due to lack of biomass at flowering and can cause the crop to mature unevenly. Plant densities that are too high can cause plants to have thin and weak stems with less branches to set pods on.
Figure 2: An example of how canola physiological structure changes with plant density. Note the plant on the left sown at low density has matured more slowly, while the plant on the right sown at high density has a tall and thin stem with few branches.
When planting both open pollinated and hybrid canola it is important to take grain weight into consideration. The size and therefore the weight of seed can vary significantly from season to season and even from paddock to paddock. The greater the seed size is, the higher the sowing rate needs to be to achieve target plant density. While purchasing seeds of smaller size may seem like more value for money, seeds of a larger size are typically more robust and have better vigour than smaller seeds.
Finally, knowing how well your seed is going to germinate will assist in reaching target plant density. While germination percentages are provided when purchasing hybrid canola seed it is important to test the germination percentage of open pollinated seed if it has been retained on farm. If you would like to have a sample tested for germination percentage, vigour and grain weight please contact your local Western Ag Agronomist.
Article produced by - Claudia Higgins, Western AG Hamilton/Willaura