PRINCIPLES OF HORTICULTURE EXAM #3 – TEXAS TECH UNIVERSITY
STUDY GUIDE, PRACTICE QUESTIONS & REVIEW 2026/2027
Nitrogen - ✔✔- Major component of plant chemicals and amino acids proteins
- Nitrogen can be a cation
- Most responsive fertilizer nutrient
- Very mobile (can take it up quickly in both the plant and soil)
Phosphorus - ✔✔- Energy transfer, germination, most aspects of plant growth
- Plant available forms: HPO4 ^-2, H2PO4^-
- Mobile in plant and immobile in the soil
Potassium (K) - ✔✔- Protein synthesis, enzyme activation, disease resistance, enhances fruiting and
flowering, water balance
- Plant available form K+
- Mobile in plants and Soil
Advantages of organic fertilizers - ✔✔- Contain more than one nutrient
- Nutrients are released slowly
- Act as soil amendments
Disadvantages of organic fertilizers - ✔✔- Usually low in nitrogen
- bulky
- manures may contain high amounts of salts (potassium, sodium, nitrates; can lead to groundwater
pollution)
Advantages of inorganic fertilizers - ✔✔- Usually concentrated, so small amounts provide necessary
nutrients
- Usually economical
- Provide plants with readily available nutrients
Disadvantages of inorganic fertilizers - ✔✔- It contains no organic matter.
- It can cause a chemical build up in soil.
- It leaches out in heavy rain or through irrigation.
- It has a high acid concentration which leads to high soil acidity.
(Often applied excessively
resulting in salt injury to plant and
resulting in excessive plant growth)
Soil Amendments - ✔✔Any material worked into the soil or applied to the surface to improve plant
growth
- improving soil structure, drainage
- increasing the soil's water and nutrient holding capacity
modifying soil pH
STUDY GUIDE, PRACTICE QUESTIONS & REVIEW 2026/2027
Nitrogen - ✔✔- Major component of plant chemicals and amino acids proteins
- Nitrogen can be a cation
- Most responsive fertilizer nutrient
- Very mobile (can take it up quickly in both the plant and soil)
Phosphorus - ✔✔- Energy transfer, germination, most aspects of plant growth
- Plant available forms: HPO4 ^-2, H2PO4^-
- Mobile in plant and immobile in the soil
Potassium (K) - ✔✔- Protein synthesis, enzyme activation, disease resistance, enhances fruiting and
flowering, water balance
- Plant available form K+
- Mobile in plants and Soil
Advantages of organic fertilizers - ✔✔- Contain more than one nutrient
- Nutrients are released slowly
- Act as soil amendments
Disadvantages of organic fertilizers - ✔✔- Usually low in nitrogen
- bulky
- manures may contain high amounts of salts (potassium, sodium, nitrates; can lead to groundwater
pollution)
Advantages of inorganic fertilizers - ✔✔- Usually concentrated, so small amounts provide necessary
nutrients
- Usually economical
- Provide plants with readily available nutrients
Disadvantages of inorganic fertilizers - ✔✔- It contains no organic matter.
- It can cause a chemical build up in soil.
- It leaches out in heavy rain or through irrigation.
- It has a high acid concentration which leads to high soil acidity.
(Often applied excessively
resulting in salt injury to plant and
resulting in excessive plant growth)
Soil Amendments - ✔✔Any material worked into the soil or applied to the surface to improve plant
growth
- improving soil structure, drainage
- increasing the soil's water and nutrient holding capacity
modifying soil pH
