MALACHITE GREEN METHOD COMPARED TO ASCORBIC-ACID FOR ESTIMATING SMALLAMOUNTS OF PHOSPHORUS IN WATER, 0.01M CALCIUM-CHLORIDE, AND OLSEN SOIL EXTRACTS

Malachite green method has been evaluated for estimating minute quanti ties of phosphorus (P) in water, 0.01M calcium chloride (CaCl2), and O lsen [sodium bicarbonate (NaHCO3)] extracts of ten soils of varying pr operties. The precision and accuracy of the malachite green method was better than that of the ascorbic acid method to estimate P in these t hree extracts. The recovery of added P ranged from 95.3-99.3% in water , 96-100% in 0.01M CaCl2, and 96.7-100% in Olsen extracts. The ascorbi c acid method underestimated the amounts of 0.01M CaCl2-P and its prec ision was also lower than the malachite green method. It is possible t o predict the P concentration in the three extracts equal to malachite green method from the ascorbic acid P values by using regression equa tions.