ASA AGRONOMY CCA
PRACTICE TEST 150
QUESTIONS
Question 1: Which element is classi�ed as an essential plant micronutrient?
Choices:
1) Zinc 2) Calcium 3) Magnesium 4) Sulfur
Correct Answer: Zinc
Explanation: Zinc is an essential micronutrient. Calcium, magnesium, and sulfur are essential macronutrients because plants require them in larger quantities.Page 1
Question 2: A corn crop shows general chlorosis beginning on the oldest leaves while the newest leaves remain greener. Which nutrient de�ciency is most consistent with this pattern?
Choices:
1) Calcium 2) Nitrogen 3) Iron 4) Boron
Correct Answer: Nitrogen
Explanation: Nitrogen is mobile in plants, so de�ciency symptoms usually appear �rst on older leaves as nitrogen is remobilized to new growth. Calcium, iron, and boron are relatively immobile and tend to a�ect younger tissue �rst.Question 3: Which nutrient is most directly associated with regulation of stomatal opening and closing?
Choices:
1) Phosphorus 2) Sulfur 3) Potassium 4) Molybdenum
Correct Answer: Potassium
Explanation: Potassium helps regulate guard-cell turgor and therefore stomatal opening and closing, which strongly in�uences plant water relations.Page 2
Question 4: Which chemical form is a major form of phosphorus absorbed by plant
roots in typical agricultural soils?
Choices:
1) P2O5
2) PH3
3) PO4+
4) H2PO4-
Correct Answer: H2PO4-
Explanation: Plants absorb phosphorus primarily as orthophosphate ions, especially H2PO4- and HPO4 2-. P2O5 is a fertilizer analysis convention rather than the form taken up by roots.Question 5: Which nutrient is generally least mobile in the soil because it is strongly sorbed or precipitated?
Choices:
1) Phosphate 2) Nitrate 3) Chloride 4) Sulfate
Correct Answer: Phosphate
Explanation: Phosphate is commonly retained by sorption and precipitation reactions, so it usually moves much less through soil than nitrate, chloride, or sulfate.Page 3