The question: Is there a perfect soybean plant and did you pick the perfect plant type this season?
The answer: In today’s modern soybean production, I don’t know if we can say there is a perfect soybean plant, however, there is a perfect placement for every soybean plant style or type.
Most modern corn hybrids have unique characteristics that are a result of combining two different inbred lines and it’s the dominance of the combination that will be visually expressed in a field. It’s these characteristics that may allow products to perform in different environments and soil conditions. Soybeans do have typical visual characteristics that help influence placement to maximize yields.
Example 1: If a soybean has a very large and bushy canopy:
- It’s most likely not going to be recommended to be placed in a very high fertility and high yielding environment. Since a soybean plant will luxury feed, it will allow the canopy to get very large and could have standability issues, which can also lead to lower sunlight interception and reduced air movement. Ultimately causing the plant to reduce seed counts or weights.
- It’s not recommended to place this bean in a low population in a wide row situation.
- This style of bean would typically perform very well under stress conditions.
- Not a good bean type for fields at risk for white mold.
- Good bean type for marginal soils and clay knobs that need as much growth as possible.
Example 2: If a soybean has a very short and narrow canopy:
- It’s most likely not going to be recommended to be placed in a wide row and stressed environment. With already having a small canopy, adding these additional issues could cause reduced sunlight interception.
- This style of soybean would also struggle to close the row, allowing weed pressures to thrive and surface moisture to evaporate due to sunlight exposure.
- Good bean type for narrow 7-, 10- and 15-inch rows.
The image to the right shows how plant density can influence the canopy and ultimately influence the potential pod development sites. We know that a lot of yield is preserved during R4-R5. However, how much yield was originally established before then is not always checked. Therefore, it’s important to make bloom and pod counts throughout the season on different varieties and agronomic systems to understand true pod dynamics over the season.
Regardless of the plant structure, it’s still up to the plant to overcome stresses (nutritional, water, disease, insect and weed pressure) to maximize the total number of nodes, blooms, and retained pods. In modern breeding programs, it’s hard to breed for specific visual characteristics while maintaining high yield potential. “I want a short bean, with a narrow canopy, with great disease package with great yield”, is not how it works. The process is more like “We have just bred this high yielding soybean variety. However, based off field trials this is the best environment to place it in.” Instead of finding the perfect beans, its more effective to place it in the perfect environment for a soybean to thrive and then add the newest best management practices.
Importance of early development: In the last few years, soybean producers have been planting earlier than typical. This can have a profound impact on how the plant accumulates dry matter, stored nitrogen, and develops pod sites and final pod counts. These factors are important because they will allow a plant to establish a higher yield potential.
What’s the Value?
- Early planting will allow for more leaf area to be exposed to solar radiation that will lead to increased dry matter accumulation.
- More nodes can be developed, producing more potential pod sites.
- Modern breeding programs have selected for varieties for seedling disease tolerance and early season vigor.
- Seed treatments have provided additional value to support a soybean during challenging environments and generally guarantee growers good stand establishment.
Quality and Quantity of Sunlight: Since a soybean plant is a sunlight and carbon factory that produces oil- and protein-rich soybeans, it’s very common to correlate the quantity of output with the quantity of the input. A 2010 study by Liu explored the relationship of pod counts and final yield to the quality of light interaction. It was noted that a decrease in radiation use efficiency was responsible for hitting “the yield ceiling,” commonly observed in population density experiments. Liu’s study showed an increase in seed yield of 71.7% from the increase in pod numbers when using a more branching variety type. Liu believes that the total pod numbers are influenced by the crop’s quality and quantity of sunlight, which is a result of the size and architecture of the canopy and the ability of light to effectively penetrate and be absorbed.
Planting date will have an extreme impact on the overall pod counts. A soybean main stem node is formed every 3.74 days (Bastidas, 2008), therefor the sooner a plant is established, the more potential pods that can be developed over the season. The goal is to have enough leaf area (LAI) to capture the greatest amount of solar radiation and the highest flower counts to exploit that radiation captured. This formula is allowing for a very strong and wide flowering window to set the maximum number of pods.
Agronomics Tip for success: Develop your own on-farm studies to evaluate which varieties will perform in your management systems. Use this information to determine how the potential pod sites or locations are influenced on a given variety or situation. Remember, the key to maximizing yields is to have good pod set and fill up the plant.
- Evaluate 3 – 4 different varieties that you will be planting on medium to large acres over the next few years.
- Evaluate these different varieties on planting dates.
- Evaluate these different varieties on different planting populations.