CH Plant Nutrition and Fertilization 2 — Questions and Answers
Question 1: Fertilizer burn on plant roots is primarily caused by high concentrations of which factor?
- Water
- Soluble salts (Correct answer)
- Organic matter
- Carbon dioxide
Correct answer: Soluble salts
Excessive soluble salts from over-fertilization create a high-osmotic-potential environment that draws water out of root cells, causing burn.
Question 2: Which fertilizer application method places nutrients directly in the root zone with minimal surface waste?
- Broadcasting
- Foliar spray
- Deep root injection (Correct answer)
- Top dressing
Correct answer: Deep root injection
Deep root injection delivers liquid fertilizer directly into the active root zone, bypassing competition from turf and reducing runoff.
Question 3: Phosphorus in fertilizers is expressed as which chemical compound equivalent on the label?
- P
- P2O5 (Correct answer)
- PO4
- H3PO4
Correct answer: P2O5
Federal law requires that phosphorus content on fertilizer labels be expressed as the oxide equivalent P2O5, even though modern soils labs report elemental P.
Question 4: A soil test reports low potassium. Which symptom would you most likely observe on affected plants?
- Purple discoloration of young leaves
- Brown scorching along leaf margins of older leaves (Correct answer)
- Pale green color of entire plant
- Stunted root growth only
Correct answer: Brown scorching along leaf margins of older leaves
Potassium deficiency typically causes marginal scorch (brown edges) on older, lower leaves because potassium is mobile and redistributed to younger tissue.
Question 5: Which nutrient application timing is most appropriate for promoting flower and fruit development?
- High nitrogen in early spring
- High phosphorus prior to flowering (Correct answer)
- High nitrogen during fruiting
- High calcium after harvest
Correct answer: High phosphorus prior to flowering
Phosphorus supports energy transfer (ATP) and promotes flower initiation and fruit set, making pre-bloom application the optimal timing.
Question 6: Soil EC (electrical conductivity) is used in horticulture primarily to measure:
- Organic matter content
- Total dissolved salts (Correct answer)
- Microbial activity
- Soil texture
Correct answer: Total dissolved salts
EC meters measure the ability of a solution to conduct electricity, which directly correlates with total dissolved salt concentration in the soil or growing medium.
CH Plant Nutrition and Fertilization 2
Fertilizer burn on plant roots is primarily caused by high concentrations of which factor?