Question

Bray No. 1 is

• A. 0.5M NaHCO\textsubscript{3} at pH 8.5
• B. 0.5N NaHCO\textsubscript{3} at pH 8.5
• C. 0.03M NH\textsubscript{4}F + 0.025N HCl
• D. 0.03N NH\textsubscript{4}F + 0.025N HCl

Hint:

Bray No. 1 is used for phosphorus extraction in acidic soils using ammonium fluoride and HCl.

Answer 1

The Correct Option is C

Bray No. 1 method is a chemical extraction procedure used for available phosphorus estimation in acidic soils, using 0.03M NH\textsubscript{4}F and 0.025N HCl as extractant.

Answer 2

Distinguishing the phosphorus-extraction methods: The options using sodium bicarbonate at pH 8.5 describe Olsen's method, used for alkaline and calcareous soils, not Bray's method, so those can be ruled out.
Between the remaining two, Bray No. 1 is defined with the fluoride reagent at a 0.03 molar concentration of ammonium fluoride combined with 0.025 normal hydrochloric acid; the fluoride complexes aluminium-bound phosphate while the dilute acid dissolves calcium-bound phosphate, making it suitable for acidic soils.
So the correct extractant composition is 0.03M ammonium fluoride plus 0.025N HCl.