Following materials can be used as... | Soil Science

ICAR JRF Soil Science 29 Jun 2024Shift 1

MCQ (Single Correct) +4 −1

Following materials can be used as ammenments in calcareous soils to reduce the calcareousness

(A) . Alluminium sulphate

(B) . Ammonium polysulfide

(C) . Elemental sulphur

(D) . Sulphuric acid

Choose the correct answer from the options given below:

(A), (6) and (D) only. (A), (B) and (C) only, (A), (B), (C) and (D). Correct (B), (C) and (D) only.

Amendments in Calcareous Soils: Calcareous soils contain free calcium carbonate ($CaCO_3$) that buffers soil pH above 7.5–8.2. Ameliorating high calcareousness requires acid-producing amendments:
Aluminium sulphate: Hydrolyzes in soil water to produce sulphuric acid and aluminum hydroxide.
Ammonium polysulfide: Undergoes microbial oxidation to yield sulphuric acid while supplying ammonium-N.
Elemental sulphur: Oxidized by soil Thiobacillus bacteria into sulphuric acid: $2S + 3O_2 + 2H_2O \rightarrow 2H_2SO_4$.
Sulphuric acid: Directly neutralizes $CaCO_3$ into soluble calcium sulphate (gypsum).
Conclusion: All four materials (A, B, C, D) are effective amendments. (Correct answer: Option 3)

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