Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, Delhi
A turbidimetric procedure for the determination of potassium with a photo-electric colorimeter (Klett) is standardised. The procedure is rapid, accurate and compares very well with that of using flame photometer. The standard curve prepared for the technique is equally sensitive over a range of 0 to 50 microgram K/ml. concentration, thus enabling the use of only one factor for calculation. The turbidimetric method worked satisfactorily for determining potassium in soil extracts obtained with (1) 10 per cent sodium acetate-3 per cent acetic acid (by volume) solution (pH 4.8), (2) 25 per cent NaNO3 solution (pH 7.0) and (3) distilled water. A 25 per cent NaNO3 solution (pH 7.0) is suggested for extracting available potassium of soil.
