Soil Science- ICAR JRF/SRF 2024

• Statement I is false: In the Indian sub-continent, drought is a recurrent climatic phenomenon; severe or moderate drought affects about one-third (not one-fifth) of the geographical area approximately once every 3 to 5 years, particularly across arid and semi-arid rainfed regions.
• Statement II is false: Over long-term meteorological records, localized meteorological and agricultural droughts occur with much higher frequency (every 3 to 8 years depending on the meteorological sub-division) rather than a rigid 15-year cycle affecting one-third of the country.
• Conclusion: Both Statement (I) and Statement (II) are false. (Correct answer: Option 2)

• Formula: Weed Control Efficiency (WCE) evaluates the effectiveness of weed management treatments relative to an untreated weedy check:

$$\text{WCE} (\%) = \frac{W_c - W_t}{W_c} \times 100$$

where $W_c$ is the weed count/density in the control plot, and $W_t$ is the weed count/density in the treated plot.

• Given Values: Control plot weed density ($W_c$) = $50\text{ weeds/m}^2$; Herbicide treated plot weed density ($W_t$) = $35\text{ weeds/m}^2$.
• Calculation:

$$\text{WCE} = \frac{50 - 35}{50} \times 100 = \frac{15}{50} \times 100 = 30.0\%$$

• Conclusion: Weed control efficiency is 30.0%. (Correct answer: Option 1)