Question

Determination of total phosphorus in soil sampkles

Answer 1

The amounts of total P extracted by Na2COa fusion and by HF and HCI04 digestion procedures from selected New Zealand soils and parent materials were compared. It is suggested that Na2COa fusion is the most reliable procedure. Digestion with HCI04 gave low results with strongly weathered materials and with samples which contained apatite inclusions within constituent primary minerals; whereas digestion with HF gave slightly low results only with samples which contained included apatite. Incomplete extraction of P by HCl04 and HF digestion procedures from samples which contained apatite inclusions was ascribed to the partial resistance to attack of the host minerals. Because of occlusion within highly crystalline iron and aluminium oxides, secondary inorganic P in ~trongly weathered soils was less readily extracted by HCI04 digestion than by Na2COa fusion or HF  Digestion