For acid phosphatase activity determination,a mixture of 1 g soil, 0.2 mL toluene, 4 mL modified universal buffer (MUB, pH 6.5), and 1 mL of 0.025 M p-nitrophenyl phosphate (p-NPP) was incubated at 37C for an hour, and then, 1 mL of 0.5 M CaCl2and 4 mL of 0.5 M NaOH were added to the mixture.