Soybeans are unique in that they produce most of their own nitrogen through rhizobium. This special skill is why they’re commonly grown to help improve soil health. Inoculants can provide an added rhizobium boost for optimal growth, while nutrient use efficiency products can help ensure soybeans are getting adequate levels of other key nutrients.View Soybean Products
What Are the Stages of Soybean Growth?
Soybeans go through several stages of vegetative and reproductive growth from their planting to full maturity. Below is a table breaking down the different stages of soybean growth. Crop staging is important because it gives growers insight into a plant’s maturity, and whether or not it’s ready for harvest. It’s worth noting that each stage is defined only when 50% or more of the plants have reached the specific vegetative or reproductive stage.
|VE||Emergence – cotyledons have been pulled through the soil surface|
|VC||Unrolled unifoliolate leaves – unfolding of the unifoliolate leaves|
|V1||First trifoliolate – one set of unfolded trifoliolate leaves|
|V2||Second trifoliolate – two sets of unfolded trifoliolate leaves|
|V4||Fourth trifoliolate – four unfolded trifoliolate leaves|
|V(n)||nth trifoliolate – V stages continue with the unfolding of trifoliolate leaves.
The final number of trifoliolate’s depends on the soybean variety and the environmental conditions
|R1||Beginning flowering – plants have at least one flower on any node|
|R2||Full flowering – there is an open flower at one of the two uppermost nodes|
|R3||Beginning pod – pods are 3/16 inch (5 mm) at one of the four uppermost nodes|
|R4||Full pod – pods are 3/4 inch (2 cm) at one of the four uppermost nodes|
|R5||Beginning seed – seed is 1/8 inch long (3 mm) long in the pod at one of the four uppermost
nodes on the main stem
|R6||Full seed – pod containing a green seed that fills the pod capacity at one of the four uppermost nodes on the main stem|
|R7||Beginning maturity – one normal pod on the main stem has reached it’s mature pod color|
|R8||Full maturity – 95% of the pods have reached their full mature color|
Tips for Growing High Yield Soybeans
Here are some tips and best practices for how to grow soybeans with a higher yield. Each planting environment will be unique, so use your best judgment when making adjustments to the cultivation and growing process.
- Planting Timing – Soybean crops thrive when planted earlier in the season, provided the soil and environmental conditions are favorable. If you want to be on the safe side, wait two to three weeks after the last frost to plant soybeans.
- Proper Seed Treatment and Inoculant Application – Applying an inoculant helps with nitrogen fixation in soybeans. For the nitrogen-fixing bacteria Bradyrhizobium japonicum to show results, retailers and growers should turn to seed inoculation. Use a soybean inoculant applicator to help with this process.
- No-Till Farming – This leads to increased organic matter in the soil, while reducing moisture losses along with fertilizer and nutrient runoff. Resultantly, no-till farming can increase soybean yields and economic returns.
- Utilize Herbicides for Weed Control – Use herbicides as needed and in a timely fashion to limit weed growth. Rotate multiple herbicides and sites of action to prevent herbicide-resistant weeds. Layer residual herbicides during the growing season.
- Ensure Soil Is Potassium and Phosphorus Rich – These are key nutrients for soybean crops. Potassium helps with starch production and photosynthesis, while phosphorus stimulates root development. Lack of these nutrients leads to stunted soybean growth, chlorosis, leaf discoloration and necrotic spots.
- Plant Narrow Rows – Research suggests that planting soybeans in narrower rows increases yields and provides certain advantages for the crops. For example, reduced moisture loss, reduced soil erosion and better use of light (due to faster canopy closure).
- Maintain the Appropriate Moisture Levels – Proper moisture levels are key for soybean seed germination and crop growth. Soybean seeds must take in 50% of their weight in water for germination to begin, and roughly 20% once the seed begins to swell. Avoid excess watering during the later reproductive stages. Note that improper irrigation leads to crop stress and irregular pod production.
- Appropriate Seeding Rates – The seeding rate will depend on many factors, such as climate, moisture availability and disease pressures. When planting rows at 15-inch spacing, a common seeding rate is between 125,000 and 140,000 seeds per acre.
Are All Fertilizers Beneficial to Soybean Yields?
Not all fertilizers will provide the same benefits to soybean crops, especially since the appropriate fertilizer will vary depending on the nutrient balance of the soil and the stages of soybean growth. In general, soybean inoculants will be the preferred and more cost-effective way to get nitrogen, rather than N-fertilizer.
Soybean crops have a high requirement for nitrogen, requiring nearly five lbs of nitrogen per bushel produced. While an N-fertilizer may seem like the obvious choice, much of the nitrogen from an N-fertilizer often fails to be available to the soybeans in the soil. As such, a soybean seed inoculant is more effective at fixing nitrogen for the plant, as well as being more economical, especially if soybeans haven’t been planted in the field in the last three years or more. Using inoculants as a soybean seed treatment has shown to increase yields by up to 10 bushels per acre, with plants having bigger, darker green leaves. Certain premium inoculants available today also offer dual benefit to the plant by providing greater growing power with biostimulants included.
How Useful Is Foliar Fertilizer for Soybean Growth?
Using foliar fertilizers when growing soybean crops can help alleviate some nutrient deficiencies. This is because foliar application avoids soil issues such as cold, drought, nutrient fixation and insufficient root growth, which each may limit absorption in soil-applied fertilizers. It’s generally recommended to apply foliar fertilizers to soybeans at lower rates and during cooler parts of the day, when burning of foliar tissues is less likely. Other benefits of foliar fertilizers for soybean growth include more efficient delivery of micronutrients, weather resistance, enhanced root development and increased crop growth rate.
Key Considerations for Soybean Crops
Soybeans are commonly used as a rotation crop to improve soil health, since they produce most of their own nitrogen through rhizobium. Inoculants can help generate nitrogen, the most required nutrient for sufficient crop growth and yield.
Soil & Temperature Requirements
The ideal soil type for soybean growth is typically well-drained, loamy soils. Soybean roots are very sensitive to acids and they like the heat. They utilize moisture very efficiently and are tolerant to moderate drought stress.
Fortunately, soybeans are fairly tolerant to insect and pest damage, but insecticides can be applied if insect populations are particularly high. If your soybeans are experiencing disease pressure, applying fungicides along with an integrated pest management plan is key.
For the most part, nitrogen is self-regulated in soybean crops. However, it should still be incorporated into your nutrient management plan.
Proper phosphorus levels are essential for plant development and can help ensure N fixation.
Soybeans require fairly high amounts of potassium, since it influences water efficiency, the number of seeds per plant and helps with disease prevention.
While soybeans are usually good at absorbing the micronutrients they need from the soil, sulfur has a tendency to fall by the wayside. Consider sulfur applications to ensure your crops are getting all the nutrients they need.
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