ISA Certified Arborist Practice Exam

What risk is associated with over-fertilizing trees?

1. Increased water absorption

2. Nutrient burn and tree stress

3. Improved fruit production

4. Reduced growth rate

The correct answer is: Nutrient burn and tree stress

Over-fertilizing trees primarily leads to nutrient burn and tree stress because excessive amounts of fertilizer can cause an imbalance in soil nutrients. When trees receive too much fertilizer, it can result in a high concentration of salts in the soil. This excessive salt can draw moisture away from the roots, leading to dehydration and stress. Nutrient burn manifests as browning or scorching of leaf edges, wilting, and other signs of distress in the tree. Additionally, trees may struggle to absorb water effectively due to the high salinity levels. This stress can weaken the tree's overall health, making it more susceptible to pests and diseases. While some may think that over-fertilizing could enhance fruit production or promote faster growth, the opposite is often true, as stressed trees tend to perform poorly in these areas.