Boron Deficiency in Soybean
Boron fertilization of soybeans has been shown to increase grain yield at many locations in several states. University researchers have found yield increases ranging from 5 to 18 bushels per acre. Boron is essential for all plant growth. Soybeans, like all legumes, have a high boron requirement.
Boron is necessary for:
- Stimulation of root growth
- Increased root nodule development for nitrogen fixation
- Increased branching and flowering
- Increased bloom retention
- Increased pod number
- Better seed development and grain yield
Soybeans are generally considered to be unresponsive to boron, and boron deficiency would only be expected on soils of very low boron status. Soybeans seem to be sensitive to boron toxicity, especially when the boron is applied to the leaves. However, yield reductions do not necessarily accompany leaf spotting and marginal necrosis caused by excessive boron accumulation.
As with many plants, the earliest sign of boron deficiency occurs in the roots. The root tips die and new roots are initiated giving a rosette appearance.
Likewise, the death of the shoot growing point is followed by prolific development of lateral shoots with brittle petioles.
How much boron is enough?
- Soybeans produced under intensive, high-yield management need boron in the fertilization program to ensure that this essential element will not be a limiting factor.
- Rates of boron fertilization should be based on yield goals along with soil tests and/or plant analyses. The chart provided gives general application rates and guidelines.
Timing your boron application
- Boron may be applied in dry or fluid blends. With dry bulk blend fertilizer, broadcasting before planting is recommended, using Granubor® 2.
- Boron in liquid suspensions may be applied broadcast before planting, banded at planting, or sidedressed, using Fertibor® in suspensions.
- Boron in liquid fertilizers may be broadcast before planting, banded at planting, sidedressed, or fertigated using Solubor®. This material may also be mixed with pesticides or applied to foliage in aqueous spray.*
- Never apply boron in direct contact with the seed.
*Foliar sprays should not exceed 0.5 lbs./acre boron per application.
*Fertigation allows timely split applications of boron when it is needed by the crop and minimizes leaching. Drip-trickle fertigation allows incremental applications of 0.1 to 0.25 lbs./acre boron through the drip system.
*The total amount of boron added in foliar sprays or split applications should not exceed the total broadcast recommendations.