Soybean yield is related to pod and seed set per acre. And soybeans have a whole lot of growing points leading to branching and flower set. Boron plays a role in growth and differentiation. Having boron available at the right time plays an important role in final pod set and production. Something to think about.

Boron is an important micronutrient in plant development, reproduction and sugar movement. Soils typically provide sufficient amounts of boron to the plant up front but in some instances it can be deficient. Because boron is needed only in very small quantities, and since an overdose can be damaging, care should be taken in its use in order to not over apply. One of many strange things with boron deficiency is it can show up one year and not the next. In addition, boron isn’t mobile in the plant. That means once it is taken up and used by the plant’s older leaves, it can’t be recycled—like nitrogen and phosphorus can—and reused to support new growth.

Soil type and condition influence nutrient availability. Poorly drained or highly weathered soils, highly variable soils and soils with a nutrient imbalance from high amounts of applied manure are good candidates for micronutrient applications. Also, high potassium soil test levels can impact boron availability. For example, a ratio of 200 to 1 is about normal, while a ratio of 2,000 to 1 can induce a boron deficiency. This might happen when a lot of manure has been applied.

Deficiencies can occur in areas of low rainfall when root activity is restricted, in alkaline or strongly acidic soils, in sandy soils or soils low in organic matter. The boron ion (borate is like nitrate) is mobile in soil and can be leached from the root zone during heavy rainfalls—especially in lighter, sandy soils. A boron soil and tissue test is available through soil testing laboratories.

Boron-deficiency symptoms first appear as growth abnormalities resulting in shortened internodes and yellowing of new leaves. Look for stunted shoots with few or no flowers. Floral buds may wither before opening, leading to abortion. To correct a soil deficiency, usually 0.5 to 2 pounds per acre of boron can be broadcast. Be wary of using it in starter or banding because high concentrations can damage seeds, seedlings and plant roots.

Boron can be applied as a foliar micronutrient either once or twice in the season. One or more foliar applications of boron over the growing season may produce better results than a one pound broadcast incorporated into the soil.

To learn more about soybeans and the importance of boron, register for the ILSoyAdvisor webinar on March 29 at 10 CDT. Dr. Nathan Slaton, Professor of Soil Fertility at the University of Arkansas will review the science of boron—soil and plant availability, plant functions requiring boron, susceptibility of soybeans to deficiency—and relate his experiences studying boron deficiency and boron fertilization of soybean in Arkansas over the last 15 years.

To register click here.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at

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About the Author: Dan Davidson

Soybean agronomist Daniel Davidson, Ph.D., posts blogs on topics related to soybean agronomy. Feel free to contact him at or ring him at 402-649-5919.