A Comparative Study on the use of Calcium Acetate Lactate, Calcium Chloride and Acidic Ammonium Acetate- Ethylene Diaminetetra Acetic Acid (AAAc-EDTA) for the Quantification of Extractable, P, K and Mg from Acidic Soils

Soils need to be tested before and after the establishments of plantations. This is because the results of a soil test gives a relative measure of the amount of nutrients available in the soil and thus are use as a base for nutrient diagnosis. The Calcium Acetate lactate (CAL) method for the extraction of available soil K and P and the CaCl2method for the extraction of available Mg were compared to the Acidic ammonium acetate- ethylene diaminetetraacetic acid (AAAc-EDTA) method for the determination of these elements in soil. A total of 130 samples were collected during a survey and analysed for K, P and Mg content after using the different extracting solutions. According to the results obtained, CAL and AAAc-EDTA methods were similar in their extracting power for P. In the case of K, the CAL method extracted only about half of the amount of K extracted using the AAAc-EDTA method. On the other hand, CaCl2 extracted about twice the amount of Mg extracted using the AAAc-EDTA method. These extraction methods were poorly correlated to each other except the methods for P. This shows that P data obtained by the two methods can be interpreted in the same way. The difference in the quantities of nutrients extracted was associated to the differences in the reaction mechanisms between the soil nutrients and the extracting solutions. There was an influence of pH and organic carbon content on the amount of K and Mg extracted. These preliminary studies indicate that the choice of the extraction procedure may depend on the resources available as well as the soil properties. However, the AAAc-EDTA extracting solution offers the advantage of extracting many nutrients and can save time and energy.