Weed Control In Soybeans: Why and When Do Farmers Spray?
This article was written for our soybean export buyers by the Sevita International Export Team. For grower-related questions, please contact your local Sevita representative.
Controlling weeds in a soybean crop is an important step to achieving high yields and preserving quality. Heavy weed populations can compete with the soybean crop for sunlight, soil nutrients, and water which can result in considerable yield losses. Good weed control starts early in the spring and continues throughout the season. Soybeans kept weed free until the fourth leaf emerges tend to be more competitive and generally yield very well. Later-season weeds must also be controlled to preserve soybean harvest quality and prevent staining.
WEED CONTROL APPROACH
Controlling weeds in soybeans is best accomplished with a systematic approach. Start the season with a clean field and finish the season with a clean field to reduce the number of weed seeds that are returned to the soil.
Farmers generally control the weeds using crop rotation, cultivation, and herbicides.
- Crop Rotation is an important tool for weed control, diseases, and soil health. Weeds are less able to adapt and compete if different crops are grown because each crop type competes with weeds differently. Learn more about crop rotation and how farmers decide what to plant every year.
- Cultivation is often used prior to planting soybeans to prepare the soil for planting and to promote good seed-to-soil contact at planting and even emergence of the seedlings. Cultivation can help kill any weeds that are already growing prior to planting.
- Herbicides are the most important and effective tool that farmers use to control weeds.
HERBICIDES – TIMING
Herbicides can be applied at four different times during the growing season:
- Pre-Plant Herbicides are applied before soybean planting. Some of these herbicides are left on the soil surface or incorporated into the soil with cultivation.
- Pre-Emergent Herbicides are applied after the soybean crop is planted but before the plants emerge from the soil.
- Post-Emergent Herbicides are applied to a standing soybean crop and control weeds that emerge in the crop throughout the growing season.
- Pre-Harvest Herbicides can be applied late in the season to dry out weeds or to speed up harvest dry down and improve quality - also known as a pre-harvest burn down.
At harvest time, heavy weed populations pose a threat to soybean quality. Weeds can continue to grow during the soybean dry-down period. The weeds' healthy plant tissue and seeds can create staining on the soybean seeds if not controlled. Weed seeds pose a contamination concern and create challenges with soybean storage aeration due to their higher moisture levels. Herbicides can be used to kill weeds before harvest to prevent staining and reduce the number of weed seeds. Herbicides may also be used to desiccate soybeans suffering from green stem issues which helps prevent additional staining.
HERBICIDES - SELECTION
Farmers try to match the correct herbicide with the weeds they observe in a production field. Each herbicide only controls certain types of weeds. Some herbicide products control a wider range of weed species than others. Sevita International has an agreed-upon list of herbicides that food-grade, Identity-Preserved soybean farmers are permitted to spray on their fields. View the list of permitted products.
Herbicides are approved for use by the government in Canada and are tested for several years to demonstrate that they are safe to use, safe for the environment, and can control the weeds listed on the label. Many of the newer herbicides have fairly low usage rates and are safe for the grower to apply. Growers often participate in training to use herbicides responsibly and safely.
At Sevita International, we encourage our food-grade, Identity-Preserved soybean growers to apply a pre-plant or pre-emerge combination of herbicides. Throughout the season, we ask them to monitor any weeds that emerge and follow up with post-emergent or pre-harvest herbicides as necessary. If the weeds are controlled well until first flower in July, generally a grower will not have many weeds to deal with at harvest.
Sevita International promotes a sustainable system of soybean production because we have a responsibility to our growers, the environment, and to our processing customers to supply high-quality Canadian soybeans for years to come.
For additional information or questions, please contact the Sevita Export team