Soybeans are a legume and therefore able to fix their own nitrogen. To do this, they need to be inoculated with Bradyrhizobium japonicum. In this area, double inoculation is strongly recommended. This is typically achieved by applying a liquid inoculant on the seed and putting down a granular at the time of planting.
In regard to seeding order, soybeans should be seeded after cereals, but before canola. Minimum soil temperature should be 8°C, with the 5-day forecast trending upwards. Recommended seeding rate is 1.5 units / acre, seeded ¾” – 1” deep.
Things to consider when choosing a field for soybeans include:
Enlist E3
As mentioned above, Enlist E3 soybeans are tolerant to glyphosate, glufosinate and 2,4-D choline. The order of applications is dependent on weeds present.
Conventional Soybeans
Conventional soybeans are essentially the same as field peas in terms of what you can spray. A single application of Viper ADV OR Odyssey Ultra Q can be made up to 3rd trifoliate.
In this area, disease and insects are usually not a big concern. Like peas, beans are susceptible to early season seedling diseases and root rots like Fusarium spp., Pythium spp., and Rhizoctonia solani[1]. Phytopthora sojae is a soybean specific disease and can occur anytime throughout the season[1][2]. These diseases can be controlled, or suppressed, by using a registered seed treatment. Cutworms and wireworms can also affect the crop in early stages[2] and can be alleviated using an insecticide seed treatment.
Grasshoppers, soybean aphid and green cloverworm can all affect soybeans in Manitoba[2]. There are multiple diseases that can infect the crop, but a fungicide is often not warranted due to the low disease pressure in this area.
Iron deficiency chlorosis is common in soybeans. It is a nutrient deficiency and causes interveinal yellowing in new leaf tissue. It is commonly caused by high carbonates, especially in wet years, but can be impacted by anything that causes the plant stress[3] (cool soil temperatures, water logging, herbicide stress, soil compaction, high soil nitrate, etc.) The plant can typically grow out of it. Foliar sprays are not effective[3].
Beans typically will dry down naturally, but if there are green spots or weed control is warranted, a pre-harvest application can be made. The following are registered.
As with any pre-harvest application, consult your grain buyer prior to applying. Read more about pre-harvest applications here.
Prairie Giants agronomists are here to help with any questions you may have and are available for in-season scouting!
Sources:
1. Manitoba Pulse & Soybean Growers. 2019. Scouting for Early Season Diseases. [Online] Available: https://manitobapulse.ca/2019/04/scouting-for-early-season-diseases/
2. Manitoba Pulse & Soybean Growers. 2016. Soybean Insect and Disease Scouting Calendar. [Online] Available: https://manitobapulse.ca/2016/04/soybean-insect-and-disease-scouting-calendar/
3. Riekman, Marla. 2024. Keating Seed Co Soybean Summit (Soil Considerations for Growing Soybeans session)