Macronutrients
Which nutrient makes plants green and drives leafy growth?
Nitrogen
What does pH measure in soil or water?
acidity or alkalinity
A 25 lb bag of 20-20-20 contains how many pounds of nitrogen?
5 lbs
Leaves turn pale green overall, starting with older leaves. What possible deficiency does this plant have?
Nitrogen deficiency
What do the three numbers on a fertilizer bag stand for?
(% N, % P₂O₅, % K₂O)
What is the difference between a macronutrient and a micronutrient in plants?
Macronutrients are needed in large amounts (N, P, K, Ca, Mg, S), while micronutrients are needed in very small amounts (Fe, Zn, Mn, Cu, B, Mo, Cl, Ni).
A soil test shows a pH of 5.0. Is that acidic, neutral, or alkaline?
Acidic
If a grower applies 200 lbs of 15-5-10 fertilizer, how many pounds of potassium oxide (K₂O) are applied?
20 lbs
Which nutrient deficiency causes purple leaves?
Phosphorus Deficiency
A fertilizer with only nitrogen and potassium but no phosphorus is called what?
Incomplete fertilizer
What are the three secondary macronutrients?
Calcium, Magnesium, Sulfur
If your soil test shows a light blue color in the phosphorus tube, what does that mean?
(think of rapidtest lab)
Low Phosphorus levels: possibly needs to be fertilized.
How many pounds of N are in 40 lb of 16-0-0?
6.4 lbs
Leaves have scorched edges that look burned, but veins remain green. Which nutrient is deficient?
Potassium
Poor chlorophyll formation and interveinal yellowing can indicate a deficiency of:
Magnesium
Which secondary macronutrient is part of chlorophyll and is essential for photosynthesis?
Magnesium
Your N test comes back low, but P and K are medium. What general growth problem might you expect in plants?
Yellowing of leaves and poor vegetative growth (nitrogen deficiency).
How many pounds of actual nitrogen are in 200 lbs of 20-10-10 fertilizer?
40 lbs
Why do growers test the pH of the soil or solution before deciding a plant has a nutrient deficiency?
Because if the pH is too high or too low, nutrients may be present but unavailable to the plant, causing deficiency-like symptoms.
Thin, weak stems and delayed maturity may be a deficiency of:
Phosphorus
If you saw scorched or burned leaf tips on your crop, which nutrient is likely deficient, and what type of fertilizer would you add to fix it?
Potassium deficiency. Add a potassium-rich fertilizer such as potash (K₂O) 0-0-10 or a high-third-number blend (like 15-5-30)
What does “deficiency symptom” mean?
Visible sign a plant lacks a nutrient
A 50 lb bag of 10-5-15 fertilizer contains how many pounds of potassium?
7.5lb
Your soil test shows a pH of 7.8. Even though soil tests show iron present, plants show interveinal chlorosis on young leaves. What is happening?
Iron or Nitrogen is “locked up” (unavailable) at high pH.
Why might a greenhouse manager choose liquid fertilizer instead of granular?
Faster uptake and easier use in fertigation systems.
Which nutrient promotes root development and flowering?
Phosphorus.
Why is drip irrigation efficient in greenhouse nutrient use?
Delivers nutrients directly to roots with little waste.
You apply 120 lb of 10-20-10 per acre. How many pounds of Phosphorus did you apply?
24 lbs
Interveinal chlorosis on new leaves usually signals a deficiency of:
Iron.
Why would a greenhouse use a high-K fertilizer near harvest?
Potassium improves fruit quality, color, and shelf life.
Which nutrient improves disease resistance and fruit quality?
Potassium.
Your rapid test shows medium nitrogen, low phosphorus, high potassium. How would you choose a fertilizer to balance this soil?
Select one higher in phosphorus, with moderate nitrogen, and little/no potassium.
40-lb bag, 18-6-12
How many pounds of N? How many pounds of P? How many pounds of K? How many pounds of Filler?
N= 7.2 lbs
P= 2.4 lbs
K=4.8 lbs
Filler=25.6 lbs
Why do greenhouse crops often show deficiencies faster than field crops?
Limited soil buffering/nutrient reserves
Why might a farmer apply lime before fertilizing?
To raise soil pH and improve nutrient availability.