8
Read the following statements about reasons for poor soil fertility in drylands
(A) . Fast weathering of minerals.
(B) . Low organic matter content.
(C) . Leaching losses of nutrients
(D) Soil salinity and alkalinity.
Choose the correct answer from the options given below:
EXPLANATION
Dryland Agriculture
- Low Organic Matter (B): High temperatures, intense solar radiation, and sparse vegetation accelerate the oxidative mineralization of organic residues, leaving dryland soils severely depleted in soil organic carbon (< 0.3–0.5%).
- Soil Salinity and Alkalinity (D): Because potential evapotranspiration (PET) far exceeds precipitation ($PET \gt \gt P$), upward capillary flow of groundwater deposits soluble sodium salts in the root zone, causing salinity and alkalinity.
- Weathering & Leaching (A & C are incorrect): Mineral weathering in drylands is extremely slow (due to lack of water), and leaching losses are negligible because rainfall rarely exceeds soil storage capacity.
- Conclusion: Statements (B) and (D) only are the primary causes. (Correct answer: Option 2)
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