Desiccation of canola is a key step in crop management that helps improve harvest efficiency, seed quality, and overall yield. Knowing when to desiccate canola is essential to avoid premature drying or delayed harvest, which can negatively impact seed moisture content, oil levels, and pod shattering. Timing the application of desiccants correctly ensures the crop reaches physiological maturity and helps reduce weed contamination and green material in the harvest. Understanding the signs of readiness and the best practices for canola desiccation can make a significant difference in crop performance and profitability.
Understanding Canola Desiccation
Desiccation in canola farming refers to the use of chemical or natural methods to accelerate the drying of the crop before harvest. This is commonly done to dry green stems and leaves, synchronize plant maturity, and allow for uniform harvesting.
Why Desiccate Canola?
- Improves harvest timing and reduces delays caused by uneven ripening
- Reduces weed interference and green matter in harvested seeds
- Decreases seed moisture for safe storage
- Prevents seed loss due to pod shattering
- Helps in managing late-season weeds that can contaminate the crop
While not always necessary, desiccation can be particularly helpful in fields with uneven maturity or heavy weed pressure.
Optimal Timing for Desiccation
The best time to desiccate canola is when the crop reaches physiological maturity, which usually occurs when 60% to 70% of the seeds in the pods on the main stem have turned color. This stage ensures that most seeds have stopped filling and will not lose quality or oil content after treatment.
Visual Indicators for Desiccation
- Seed Color Change: 60-70% of seeds in the main stem pods should have changed from green to brown, black, or reddish-brown
- Pod Firmness: Mature pods should be firm but not brittle, and seeds should rattle when shaken
- Plant Color: Leaves and stems may begin to yellow or dry naturally, especially on the lower parts of the plant
Scouting the field at different locations is important to ensure uniform maturity before making desiccation decisions.
Desiccation Methods
There are two main approaches to desiccating canola: chemical desiccation and natural drying through swathing or environmental factors. Each method has its advantages, depending on field conditions, equipment, and weather patterns.
Chemical Desiccation
- Uses herbicides such as diquat, glufosinate, or saflufenacil to dry the plant quickly
- Usually sprayed when the crop reaches 60-70% seed color change
- Effective against green stems and late-season weeds
- Harvest can begin within 4 to 14 days, depending on weather and product
Swathing (Windrowing)
- Involves cutting the canola and laying it in windrows to dry naturally
- Best done at 30-40% seed moisture with majority seed color change
- Helps avoid losses from pod shatter in non-shatter-resistant varieties
- Requires good drying weather and careful timing
Choosing between chemical and physical desiccation depends on crop condition, available equipment, and the grower’s harvest schedule.
Risks of Early or Late Desiccation
Timing is everything when it comes to desiccating canola. If done too early or too late, it can negatively affect seed development and harvest outcomes.
Desiccating Too Early
- Seeds may not have completed filling, leading to reduced weight and oil content
- Higher levels of green or immature seeds can lower market grade
- Increased risk of seed shriveling and quality degradation
Desiccating Too Late
- Pods may start to shatter, leading to seed loss before harvest
- Delayed harvest could expose the crop to bad weather, mold, or lodging
- Weeds may mature and contaminate seed with excess moisture or debris
Accurate field monitoring and use of the seed color change method help minimize these risks.
Field Scouting Tips for Desiccation Timing
Scouting should begin about three weeks before the anticipated harvest window. Check multiple areas of the field and assess plants from the top, middle, and bottom sections of the canopy.
How to Scout Effectively
- Pick 10 plants from random locations across the field
- Open several pods from the main stem of each plant
- Evaluate seed color and firmness
- Average the percentage of brown or black seeds
- Note the condition of stems and presence of green matter or weeds
Repeat scouting every 23 days during the critical ripening window to determine the ideal time for desiccation or swathing.
Choosing the Right Desiccant Product
Different chemical desiccants work in different ways. Some dry the crop faster, while others also target broadleaf weeds. Always check product labels and follow regulations on pre-harvest intervals.
Common Desiccants Used in Canola
- Diquat: Fast-acting, often allows harvest within 47 days
- Glufosinate: Effective on weeds, slower drying of crop
- Saflufenacil: Broadleaf weed control and plant drying in one application
Some products may have restrictions based on weather, crop stage, or export markets. Always consult with an agronomist or crop advisor before application.
Post-Desiccation Management
After applying a desiccant, it’s important to monitor crop condition daily. Desiccation accelerates drying, but weather, plant density, and soil moisture still affect readiness.
Post-Application Steps
- Check seed moisture before harvesting target below 10% for storage
- Inspect for uneven dry-down across the field
- Avoid harvesting during rain or high humidity to reduce spoilage risk
- Clean harvesting equipment to prevent contamination from weed seeds or residues
Timely and careful harvesting after desiccation ensures high-quality canola seed with minimal losses and contamination.
Knowing when to desiccate canola is a critical decision that impacts yield, quality, and harvest efficiency. The ideal time is when 60-70% of seeds on the main stem have turned color, indicating physiological maturity. Desiccation, whether chemical or by swathing, helps dry green material and synchronize ripening, especially in uneven fields or weedy areas. However, poor timing can reduce seed quality and increase shatter losses. By scouting fields thoroughly, selecting the right desiccant, and monitoring weather conditions, growers can maximize the benefits of desiccation and achieve a cleaner, higher-value canola harvest.