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Agronomy QUESTION #2066
Question 1
The response of crops to micronutrient application follows which relationship, making diagnosis and management more complex than macronutrients?
  • A linear response with no upper toxicity threshold
  • A Mitscherlich-type diminishing returns curve identical to macronutrients
  • A 'Piper-Steenbjerg effect' or Gaussian curve — deficiency at low concentrations, optimum growth at adequate supply, and toxicity (reduced growth) at high concentrations — with a very narrow sufficiency range✔️
  • A step function where deficiency disappears immediately at the critical concentration
Correct Answer Explanation
Micronutrient response follows a bell-shaped or Gaussian curve: deficiency → optimum → toxicity over a narrow concentration range. This is particularly pronounced for B, Mn, Cu, and Mo. The narrow window between deficiency and toxicity makes micronutrient management far more precise and challenging than macronutrient management.