Which of the following is true?

Correct option is A

✅ Why option (a) is correct
· Sulphur (S) application lowers soil pH due to oxidation.
· Molybdenum (Mo) availability decreases with decreasing pH.
· Hence, with S application:
· Soil becomes more acidic
· Mo uptake by plants is reduced
· This is a well-known antagonistic interaction between S and Mo.
❌ Why other options are incorrect
· (b) Boron toxicity decreases with decreasing calcium concentration
· Incorrect.
· Calcium reduces boron toxicity by limiting B uptake.
· Decreasing Ca actually increases B toxicity.
· (c) Iron plays a synergistic role in relation to zinc
· Incorrect.
· Fe and Zn are antagonistic, not synergistic.
· Excess Fe reduces Zn uptake and vice versa.
· (d) High copper in soil cause dieback in citrus
· Incorrect.
· Dieback in citrus is mainly due to copper deficiency, not toxicity.
�� Key Points
· S–Mo interaction → antagonistic
· Ca reduces B toxicity
· Fe–Zn interaction → antagonistic
· Cu deficiency → citrus dieback
✔️ Final Answer: Option (a)