Question:medium

Immediately after application (injection) of anhydrous \(\text{NH}_3\) into soil, it moves laterally as well as vertically (limited to \(< 5 \text{ cm}\)), and a localized zone known as \(\text{NH}_3\) retention zone is formed. A number of temporary yet dramatic changes occur in the \(\text{NH}_3\) retention zone. These are:
(A). A retention zone of both ammonia (\(\text{NH}_3\)) and ammonium (\(\text{NH}_4^+\)) having circular to oval shape (3-13 cm diameter) is formed.
(B). The concentration of both \(\text{NH}_3\) and \(\text{NH}_4^+\) increased in the range of 1000-3000 ppm.
(C). The pH increased up to 9.0-9.5 in the vicinity of the point of application.
(D). Concentration of \(\text{NO}_2^-\) (nitrite) increased to toxic levels (100-300 ppm).
Choose the correct answer from the options given below:

Show Hint

Anhydrous ammonia injection temporarily sterilizes a small zone of soil around the injection point because of the high pH (\(>9\)) and free ammonia toxicity. Normal microbial activity returns as the pH drops over time.
  • (A), (B) and (D) only.
  • (A), (B) and (C) only.
  • (A), (B), (C) and (D).
  • (B), (C) and (D) only.
Show Solution

The Correct Option is C

Solution and Explanation

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