• DRIS (Diagnosis and Recommendation Integrated System): Developed by E.R. Beaufils in 1973 for sugarcane and later calibrated across various field and orchard crops.
• Methodology: Evaluates plant nutritional status by comparing nutrient elemental ratios (e.g., N/P, N/K, P/K) with calibrated standard norms derived from high-yielding populations, minimizing dilution and concentration effects caused by plant age or dry matter accumulation. (Correct answer: Option 3)
• Olsen: Developed the sodium bicarbonate method for available phosphorus extraction in alkaline soils.
• Liebig: Formulated the Law of the Minimum (1840).
• Arnon: Formulated the Criteria of Essentiality of plant nutrients with Stout (1939).

• Step 1: Calculate Net Irrigation Requirement ($NIR$):

$$\text{Consumptive Use } (CU) = 125\text{ cm} = 1.25\text{ m}$$ $$\text{Effective Rainfall } (R_e) = 80\% \times 600\text{ mm} = 480\text{ mm} = 0.48\text{ m}$$ $$NIR = CU - R_e = 1.25 - 0.48 = 0.77\text{ m}$$

• Step 2: Calculate Field Irrigation Requirement ($FIR$):

$$\eta_a = 50\% = 0.50 \implies FIR = \frac{NIR}{\eta_a} = \frac{0.77}{0.50} = 1.54\text{ m}$$

• Step 3: Calculate Gross Irrigation Requirement at Headworks ($GIR$):

$$\eta_c = 70\% = 0.70 \implies GIR = \frac{FIR}{\eta_c} = \frac{1.54}{0.70} = 2.20\text{ m}$$

• Step 4: Calculate Total Diverted Volume for 1000 ha:

$$\text{Area} = 1000\text{ ha} = 1000 \times 10^4\text{ m}^2 = 10^7\text{ m}^2$$ $$\text{Volume} = 2.20\text{ m} \times 10^7\text{ m}^2 = 2.2 \times 10^7\text{ m}^3 = 22\text{ Mm}^3$$

• Conclusion: Total volume required to be diverted is 22 Mm³. (Correct answer: Option 2)