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Unlike corn, soybean plants have only a small area in which to store nutrients, making them more susceptible to in-season shortages. Providing your soybean crop with adequate nutrients will help maintain plant health and increase the efficiency of photosynthesis at the critical flowering and reproductive stages. Here are some tips for ensuring your soybean plants are adequately fed all season long.

Manganese for efficient photosynthesis
As the soybean plant approaches flowering (V3 to V5), photosynthesis is in full gear. Maintaining a sufficient level of manganese during this stage produces more flowers and a healthier plant going into the reproductive stage.

Take a tissue sample between V3 and V5 to help identify low levels of manganese and other essential plant nutrients, and to correct deficiencies early in the growth cycle, before yield potential is compromised.

Replenish low nitrogen
A tissue sample taken between V3 and V5 will also tell you if the plant has sufficient nitrogen to fully support flower production. If the tissue sample indicates low nitrogen, dig up a few plants, cut open the nodules, and check for a healthy pink to red color to ensure they’re producing nitrogen. If the color is white, brown or green, nitrogen fixation is not occurring.

In a high-yield environment, soybean plants use more than 300 pounds of nitrogen to produce 65 bushels per acre or more. Even under the best growing conditions, a soybean plant can only produce about 260 pounds of nitrogen, leaving a 40-pound deficit. In a high-yield environment, a yield response has been seen with nitrogen applications at R1 to R3 to supplement nitrogen-fixing nodules.

In average yield environments that support up to 55 bushels per acre, soybeans may not require additional nitrogen. Bottom line: That tissue sample can help you make a decision about whether or not nitrogen supplementation is needed.

Monitor ongoing nutrient needs
As the reproductive stage progresses, it becomes even more important to support efficient photosynthesis. The plant needs to take in as much sunlight as possible and convert it to sugar to nourish new soybeans developing at each node.

Manganese continues to play an important role in maintaining efficient photosynthesis throughout the season. And an adequate supply of boron will help keep flowers and pods healthy longer. You should also monitor calcium and potassium to support ongoing plant health.

Tissue sampling between R1 and R3 will identify any micronutrient shortages while there’s still time to make supplemental applications and protect yield potential.

Stave off disease
Keeping plant leaves disease-free allows the maximum amount of photosynthesis. Diseases such as frogeye leaf spot or brown spot can prohibit adequate sunlight from entering the plant and diminish the production of sugars that feed pods.

A fungicide application during the R1 to R3 stage not only prevents leaf diseases, it helps the plant use water more efficiently and better tolerate dry conditions.

For more information about soybean management for your area, contact your local agronomist.

Quick tips for soybean health
1. Maintain manganese levels to help increase the efficiency of photosynthesis.
2. Take a tissue sample to measure nitrogen levels.
3. Monitor ongoing nutrient needs to protect yield potential.
4. Keep soybeans free of disease to allow the maximum amount of photosynthesis.

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