For pea growers, timing is everything when it comes to harvesting a high-quality crop. One of the most critical decisions during the growing season is determining when to desiccate peas. Desiccation is the process of applying a chemical or mechanical method to accelerate the drying of the crop before harvest. It helps to ensure uniform ripening, reduces the moisture content of seeds, and can make harvesting easier and more efficient. Understanding when to desiccate peas can directly impact the yield, quality, and overall market value of the crop.
Understanding Desiccation in Pea Production
What Is Desiccation?
Desiccation refers to the intentional drying of a crop by using either chemical desiccants or natural methods such as cutting and windrowing. In peas, desiccation is often used to promote uniform drying and to stop further growth, which can reduce the risks associated with delayed harvests such as mold, seed staining, or shattering.
Why Desiccation Is Important
Proper desiccation offers several benefits to pea growers:
- Improves seed quality by preventing uneven maturity
- Reduces the likelihood of weather-related losses
- Helps in scheduling timely and efficient harvest
- Minimizes green material that may interfere with harvest equipment
Optimal Timing for Desiccation
Stage of Crop Development
The best time to desiccate peas is when the crop has reached the proper stage of physiological maturity. This means most of the seeds have hardened, and the pods have turned a uniform color. The correct timing usually occurs when:
- 75% to 80% of the pods on the plant have turned yellow or tan
- The bottom pods are dry and rattle when shaken
- The seeds inside are firm and no longer contain milky liquid
Desiccating too early can result in shriveled or immature seeds, while waiting too long may increase the risk of pod shattering and seed loss.
Visual Signs in the Field
Here are a few visual cues that can help determine the right time for desiccation:
- Lower pods are dry and starting to split naturally
- Middle pods are yellow to brown and seeds are hard
- Upper pods may still be green but are no longer filling
- Leaves have started to yellow or fall off
Seed Moisture Content
Checking the seed moisture content is another helpful method. Ideal seed moisture for desiccation is around 30% or slightly lower. If the moisture is significantly higher, desiccating may lead to poor drying or seed damage.
Methods of Desiccation
Chemical Desiccation
Chemical desiccants are commonly used in commercial pea production. These products stop the growth of the plant and speed up drying. Commonly used desiccants include:
- Diquat: Fast-acting and widely used for peas
- Glyphosate: Can be used but must be applied when seeds are mature
When using chemicals, it’s important to follow label instructions and observe the pre-harvest interval (PHI), which is the number of days required between application and harvest. PHIs vary depending on the product.
Natural Desiccation and Windrowing
Some growers prefer mechanical methods such as swathing or windrowing, especially in organic systems where chemical use is restricted. In this method, the plants are cut and left to dry in rows before being picked up by a combine. This method requires dry weather conditions to be effective and carries a higher risk of losses due to wind or rain.
Environmental and Field Considerations
Weather Conditions
Weather plays a significant role in desiccation timing. Ideal conditions for chemical desiccation include dry weather with low humidity and moderate temperatures. Rain soon after application can reduce effectiveness, while very hot weather may cause the desiccant to work too quickly, leading to uneven drying.
Field Uniformity
Uniform crop maturity across the field is ideal. If the crop is uneven, consider targeting desiccation based on the average maturity level. Alternatively, fields may be divided and desiccated in stages to avoid sacrificing the quality of more mature areas or forcing immature parts to dry prematurely.
Crop Variety
Some pea varieties mature more uniformly than others, which can influence desiccation decisions. Check with your seed supplier for information on the variety you are growing. Shorter-season peas tend to mature evenly and may respond better to desiccants.
Potential Risks of Improper Timing
Seed Damage
If peas are desiccated too early, the seeds may not reach full maturity. This results in wrinkled, undersized, or low-germination seeds, which are not suitable for storage or sale as seed stock.
Residue and Compliance
Incorrect use of desiccants can result in chemical residues that exceed regulatory limits. This is particularly important if the peas are intended for human consumption or export. Always follow proper application rates and PHI guidelines to avoid residue issues.
Reduced Yield
Early desiccation may stop seed filling, leading to lower yields. Late desiccation increases risks of pod shattering and seed loss, especially during windy or stormy conditions.
Best Practices for Desiccating Peas
- Scout fields regularly during late growth stages
- Check multiple plants across the field for uniformity
- Use a moisture meter or hand shell seeds to test for maturity
- Record application dates and monitor weather forecasts
- Keep equipment calibrated and maintained for even application
Harvest Timing After Desiccation
Depending on the method used and weather conditions, peas are typically ready to harvest 4 to 10 days after desiccation. Monitor pods and seeds daily to determine when they are dry enough for safe harvest and storage. Seeds should be harvested when they reach around 18% moisture content for safe handling and further drying.
Knowing when to desiccate peas is essential for preserving seed quality and maximizing yield. The decision should be based on a combination of visual indicators, seed moisture levels, field uniformity, and environmental factors. Whether using chemical desiccants or mechanical methods, proper timing allows for a more efficient and successful harvest. With careful observation and good field management, desiccation can be a valuable tool in pea production, leading to higher-quality crops and reduced losses at harvest.