MCAER PG CET 2026: Agronomy

Time Left: 100s

1. Which of the following is the correct physiological basis for the "Negative Priming Effect" in soil organic matter decomposition?

• Preferential utilization of added substrate by microbes
• Accelerated decomposition of native SOM
• Competitive inhibition of extracellular enzymes
• Nitrogen immobilization leading to toxicity

Correct: A. Negative priming occurs when microbes switch from decomposing stable soil organic matter (SOM) to the more easily available fresh organic matter added.

2. [PYQ 2021] The concept of 'Relative Growth Rate' (RGR) was first proposed by:

• Blackman
• Gregory
• Watson
• Williams

Correct: A. V.H. Blackman (1919) proposed the RGR, often referred to as the 'Efficiency Index' of the plant.

3. In the context of herbicide resistance, the 'Target Site Mutation' usually involves which mechanism?

• Enhanced sequestration in vacuoles
• Metabolic degradation by Cytochrome P450
• Alteration in the enzyme binding site
• Reduced translocation via phloem

Correct: C. Target site resistance occurs when a mutation changes the shape of the enzyme the herbicide targets, preventing the herbicide from binding.

4. Which moisture stress index accounts for both rainfall and potential evapotranspiration to define drought intensity?

• Aridity Index (AI)
• Palmer Drought Severity Index (PDSI)
• Moisture Adequacy Index (MAI)
• All of the above

Correct: D. All these indices integrate supply (rain) and demand (PET) to quantify moisture stress.

5. [PYQ 2023] The term 'Tillage' is derived from which language?

• Latin
• Anglo-Saxon
• French
• Greek

Correct: B. Tillage is derived from the Anglo-Saxon words 'tilian' and 'teolian', meaning to strive after or cultivate.

6. The 'Thermic' soil temperature regime indicates a mean annual soil temperature range of:

• 8°C to 15°C
• 15°C to 22°C
• 22°C to 28°C
• Above 28°C

Correct: B. Thermic regimes range from 15-22°C, while Hyperthermic is >22°C.

7. Calculate the Crop Water Use Efficiency (WUE) if the yield is 5000 kg/ha and Evapotranspiration (ET) is 500 mm.

• 1.0 kg/ha-mm
• 10.0 kg/ha-mm
• 100.0 kg/ha-mm
• 0.1 kg/ha-mm

Correct: B. WUE = Yield / ET. So, 5000 / 500 = 10 kg/ha-mm.

8. Which law states that the "yield is limited by the nutrient present in the minimum quantity relative to plant requirements"?

• Mitscherlich's Law
• Liebig’s Law of Minimum
• Wilcox's Inverse Yield Law
• Macy's Law

Correct: B. Justus von Liebig proposed this in 1840; the barrel analogy is often used to explain it.

9. In Conservation Agriculture, what is the minimum soil surface cover required by crop residues?

• 15%
• 30%
• 50%
• 75%

Correct: B. 30% is the globally accepted minimum threshold for defining conservation tillage/agriculture.

10. 'Hidden Hunger' in plants refers to:

• Nutrient deficiency with severe symptoms
• Nutrient content below critical level but without visual symptoms
• Excessive nutrient uptake causing toxicity
• Water stress during flowering

Correct: B. It is a state where the plant's yield is reduced due to low nutrient concentration, yet no visual deficiency symptoms appear.