Canola Stand Issues and Reseeding Decisions
Each year emerging canola fields can be subject to damage resulting from frost, wind, hail, seedling diseases and/or insects. In most cases it results in a few lost plants, but in some cases it may reduce plant stands dramatically and questions arise about re-seeding.
Re-seeding an entire field or a large portion of the field can be a difficult decision as it requires additional time, expense and final results are not guaranteed to be better than the initial stand. Before making the final decision to re-seed, first assess how many plants are left. As a guide, 4 canola plants/ft² early in the season (prior to 4 leaf stage) is the minimum plant stand recommendation. Canola can compensate and still branch out/fill in the canopy at this density. Below this count, there is greater risk that the crop will be out-competed by weeds, will not fill in the canopy properly and be more at risk to hot/dry conditions at flowering.
Next, determine the cause of the damage. Is the damage from a single event (excess wind, frost) or a potentially on-going issue (seedling disease, excess saturated soils, suspected herbicide residue injury). Is the re-seeded field going to be susceptible to the same damage? If so, maybe re-seeding back to canola is not the wisest decision. Also, how bad is the damage? Are the remaining plants going to be able to grow through the damage with time? Is the growing point still healthy? If so, crop development may be delayed, but the crop will still bloom, mature and be harvested earlier than if the area is re-seeded.
If you were to re-seed – what soil moisture are you seeding into? Soil moisture must be available to the re-seeded crop to ensure quick uniform germination and emergence. If the seedbed is dry, seed and seedling can become stranded, resulting in slow or patchy emergence. If soil moisture is excessive, replanting may not be possible as fields cannot be travelled on. In both situations, if the existing stand still has the 4 plants/ft2 and can grow through damage, it may be wise to leave the existing stand.
If the plant population is close to or below the recommended plant stand, plants do not look like they will be able to survive the damage, and soil conditions are good, re-seeding is a very wise choice. If you have a contract of insurance with MASC, you will need to contact an adjustor to come and assess the field to make sure you are eligible for the re-seed indemnity. As well, for MASC purposes and for your own knowledge, a ‘check’ strip must remain of the original plant stand and condition in a representative area of the field. An area of 10 feet wide and the full length of the field, or as advised by the MASC agent. This check can help you gauge, if future situations arise, the viability of keeping or leaving a damaged lower population crop at the calendar date you are at.