Certified Arborist Practice Exam

Which chemical form of Iron and Manganese may be unavailable to trees in alkaline soil?

1. Alkaline

2. Acidic

3. Buckeye, Horsechestnut

4. Soil

The correct answer is: Alkaline

In alkaline soils, the chemical forms of iron and manganese can become less available to plants, including trees. The solubility of these micronutrients is influenced by the pH level of the soil; as pH increases into the alkaline range, the availability of iron and manganese decreases. Iron, in particular, tends to form insoluble compounds in alkaline conditions, making it difficult for trees to absorb. The other options provided do not directly refer to the chemical forms of iron and manganese related to soil pH levels. They pertain instead to either irrelevant classifications or contexts that do not address the specific conditions affecting the availability of these nutrients in alkaline soils. Thus, recognizing that alkaline conditions lead to reduced availability of iron and manganese confirms that alkaline is indeed the correct answer.