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Fresh green soy plants on the field in spring.

Cristie Preston, Ph.D.

Compared to corn, legume crop production thrives under slightly higher pH (6.2 to 6.8). Legumes, like soybean and alfalfa, form symbiotic relationships with rhizobia to form nodules in roots that biologically fix nitrogen. If the soil pH is too low, this can negatively affect the rhizobia relationship and can inhibit nodule development. In general, bacteria tend to thrive in higher pH.

A previous article on pH showed the ideal range of 5.5 to 6.5 based on nutrient availability. When a farmer is determining what final pH he/she is liming to, the crops grown in the rotation need to be considered. Soybean yield may be negatively affected if the soil pH is too low.