ISA Certified Arborist Practice Exam 2025 - Free ISA Arborist Practice Questions and Study Guide

Organic fertilization is the term used to describe organic materials that are carbon-based and decompose slowly. Leaching (choice A) refers to the process of nutrients being washed away from the soil, which does not directly relate to organic material. Urea-formaldehyde (choice C) is a synthetic fertilizer that does not fall under the category of organic materials. Complete fertilizer (choice D) refers to a type of fertilizer that contains all three primary nutrients (nitrogen, phosphorous, and potassium) but does not necessarily have to be organic. Therefore, organic fertilization is the most accurate term to describe the given description.