Methods

Solution

Soil to solution ratio (W/V)

Extraction time

Reference

Olsen

0.5 M NaHCO₃, pH 8.5

1:20

30 min at 120 strokes per minute

[2]

Mehlich-3

0.2 N CH₃COOH + 0.013 N HNO₃ + 0.015 N NH₄F + 0.25 N NH₄ NO₃ + 0.001 M EDTA

1:10

5 min at 180 strokes per minute

[3]

Kelowna

0.2 N CH₃COOH + 0.013 N NH₄F

1:10

15 min at 180 strokes per minute

[4]

Bray and Kurtz-1

0.03 N NH₄F + 0.025 N HCI

1:10

5 min 120 strokes per minute

[18]