ISA Soil Management & Fertilization Techniques 2

Question 1

What is the difference between slow-release and controlled-release fertilizers, and which is generally preferred for landscape trees?

Accepted Answer

Slow-release depends on microbial breakdown; controlled-release uses coated granules with predictable release rates — both are preferred over quick-release for trees

Answer

Slow-release fertilizers (often organic) depend on soil microbes for nutrient release, which varies with temperature and moisture. Controlled-release fertilizers use polymer coatings for predictable release. Both provide extended nutrition and are preferred over quick-release for trees.

Question 2

What is the significance of the carbon-to-nitrogen (C:N) ratio when applying organic mulch or amendments to tree root zones?

Accepted Answer

High C:N materials like fresh wood chips can temporarily tie up soil nitrogen as microbes decompose them, potentially causing nitrogen deficiency in trees

Answer

When high-carbon, low-nitrogen organic materials (C:N >30:1) are incorporated into soil, decomposing microbes draw nitrogen from the surrounding soil to process the carbon, temporarily reducing nitrogen available to tree roots.

Question 3

Why should a complete soil test be conducted before prescribing a fertilization program for landscape trees?

Accepted Answer

To identify actual nutrient deficiencies and avoid applying unnecessary nutrients that waste money, may harm the tree, and contribute to environmental pollution

Answer

Soil testing reveals actual nutrient levels, pH, and organic matter content, allowing targeted fertilization that addresses real deficiencies rather than applying unneeded nutrients that can disrupt nutrient balances, encourage disease, or pollute waterways.

Question 4

What is the proper timing for fertilizing deciduous trees in most temperate climates?

Accepted Answer

Late fall after leaf drop or early spring before bud break, when roots can absorb nutrients without supporting active shoot growth

Answer

Fertilization is most effective in late fall (after leaf drop, while soil is still warm) or early spring (before bud break). Late fall applications allow root absorption and storage; spring applications support the flush of new growth.

Question 5

How does soil compaction affect fertilizer effectiveness in the tree root zone?

Accepted Answer

Compaction reduces water infiltration, restricts root growth, and limits microbial activity — all of which decrease the tree's ability to access and absorb applied fertilizers

Answer

In compacted soil, water carrying dissolved fertilizer cannot infiltrate effectively, roots cannot proliferate to access nutrients, and reduced microbial activity slows the release of organic nutrient forms. Decompaction should precede or accompany fertilization in compacted sites.

(ISA) ISA Certified Arborist Practice Test

(ISA) ISA Certified Arborist Practice Test

ISA Soil Management & Fertilization Techniques 2