Last week, I reported damage from deer was one of the factors contributing to poor ratings in soybean fields. I have seen signs of deer grazing on young soybean plants from St. Mary to Madison parish. I was asked how much yield loss should be expected from deer grazing. After a brief literature review, I can suggest the effect of deer grazing could decrease yield up to 74% or more. However, there are also reports of no decrease in yield after deer grazing. If the grazing is minimum, the soybean plant should be able to compensate. An article in the Volume 10, Issue 3 – April 2020 of the LA Crops Newsletter, “Considerations for replanting soybean,” explains that the growing point in soybean plants is above the two cotyledons. On the top of the main stem there is a growing point called the apical meristem. Normally, the apical meristem directly influences the architecture of the plant by controlling the growth habit. With the original apical meristem intact, the soybean plant will grow predominantly upward by the main stem increasing in height (Figure 1). If the apical meristem is cut, soybean plants have axillary buds along the main stem (Figure 2). These axillary buds may remain dormant or can produce axillary branches capable of producing trifoliolate leaves and reproductive structures (Figure 3). Of course, that is if the deer do not continue to feed on the new growth.

Figure 1. A soybean plant with one main stem above the hypocotyls.

Figure 2. A soybean plant with the apical meristem cut above the cotyledons by deer grazing.
The plant is growing two axillary branches from the axils in between the cotyledons and the original main stem.

Figure 3. A soybean plant with the apical meristem cut above the unifoliate leaves. The plant is
growing two axillary branches from the axils between the unifoliate leaves and the main stem.