Which of the following is typically considered a micronutrient in soil testing for rangelands?

• A. Zinc
• B. Nitrogen
• C. Phosphorus
• D. Calcium

Answer: (A)

Understanding nutrient categories in soil helps explain why zinc is the micronutrient in this context. Plants require certain elements in much smaller amounts—micronutrients—and others in larger amounts—macronutrients. Nitrogen, phosphorus, and calcium are classic macronutrients (with calcium also considered a secondary macronutrient due to the larger quantities plants need). They’re required in relatively high amounts for growth and reproduction.

Zinc, on the other hand, is needed only in trace amounts, which is the hallmark of a micronutrient. It plays essential roles in enzyme function and growth processes, and soils with too little zinc can lead to poor forage development. Availability of zinc in soil is influenced by factors like pH and organic matter; for example, higher pH or alkaline conditions can reduce zinc solubility, making it harder for plants to take up.

So in the context of rangeland soil testing, zinc is the micronutrient being tested for, whereas nitrogen, phosphorus, and calcium are considered macronutrients (with calcium as a secondary macronutrient).