Soil Science- ICAR JRF/SRF 2024

• Statement (A) is correct: Traditional aerial photographs captured on photographic film represent continuous-tone analog imagery.
• Statement (B) is correct: Satellite imagery captured via electronic optical-mechanical scanners and CCD array detectors is natively digital.
• Statement (C) is correct: Digital images are structured as regular two-dimensional grids of pixels, each assigned a numerical Digital Number (DN) corresponding to radiance.
• Statement (D) is incorrect: The French SPOT satellite series is a multispectral system (operating in 3–4 broad optical bands), whereas hyperspectral sensors record hundreds of narrow, contiguous spectral bands (e.g., AVIRIS, Hyperion).
• Conclusion: Statements (A), (B), and (C) only are correct. (Correct answer: Option 4)

• Unsupervised Image Classification: Algorithms that automatically group multispectral image pixels into natural spectral clusters based purely on statistical Euclidean distance without analyst-defined training areas.
• K-means Clustering Algorithm: A classic iterative unsupervised clustering algorithm that partitions $N$ observations into $K$ clusters by minimizing within-cluster sum of squares.
• Supervised Algorithms: Parallelepiped, Minimum distance to means, and Maximum likelihood classification are supervised methods requiring user-defined training sites. (Correct answer: Option 3)

• Statement (I) is True: The Uniformity Coefficient ($C_u$) in soil mechanics and soil physics is defined as the ratio of $d_{60}$ (particle diameter corresponding to $60\%$ finer by weight) to $d_{10}$ (effective diameter, $10\%$ finer): $C_u = \frac{d_{60}}{d_{10}}$.
• Statement (II) is False: A well-graded loamy soil contains a wide spectrum of particle sizes across gravel, sand, silt, and clay, resulting in a large $d_{60}/d_{10}$ ratio ($C_u \gt 4 - 6$); uniformly sized single-grained sand has $C_u \approx 1 - 2$. Thus, well-graded loam has a higher uniformity coefficient than uniform sand, not lower.
• Conclusion: Statement (I) is true but Statement (II) is false (Option 3).

Correct option: (3) Statement (I) is true but Statement (II) is false.

• Physical Parameters in Soil Physics and Their Dimensional Units:
• Sorptivity ($S$): Governs initial capillary infiltration ($I = S t^{1/2}$); measured in $\text{cm}\cdot\text{s}^{-1/2}$ $\rightarrow$ (I)
• Matric Suction ($\psi_m$): Capillary energy of soil water; expressed as equivalent hydraulic head in $\text{cm}$ of water $\rightarrow$ (II)
• Soil Hydraulic Diffusivity ($D = K \frac{d\psi}{d\theta}$): Measured in $\text{cm}^2\cdot\text{s}^{-1}$ $\rightarrow$ (III)
• Soil Wetness Gradient ($\frac{d\theta}{dx}$): Moisture change per unit length; unit is $\text{cm}^{-1}$ $\rightarrow$ (IV)
• Systematic Match: (A)-(I), (B)-(II), (C)-(III), (D)-(IV) corresponds to Option 1.

Correct option: (1) (A) - (Il), (B) - (IV), (C)- (), (D) -