Trace elements

The elements Cu, Fe, Mn and Zn (also Ca) are analysed by the methods of Chapman and Pratt (1961) and also Perkins (1970). Perkins extracted 5 g air-dried soil (collected using an aluminium auger), sieved through a 2-mm stainless-steel mesh, with 20 ml of a solution of 0.05 M HCl plus 0.0125 M H2SO4 in a 250-ml large-mouth polythene bottle, and shaken on an Eberbach reciprocating shaker for 15 min at 280 oscillations per minute. It was filtered through a Whatman No. 44 paper through polypropylene funnels into polypropylene bottles (this should be modified to reject the first few millilitres of filtrate). The former extracting agent was originally chosen by Perkins because it was also used by many mid- and south-Atlantic states for extraction of P, K, Ca and Mg; whether it is appropriate in other locations should be determined. The detection of excessive amounts of Zn could arise from residues in sewage sludge or poultry manure. High Mn, or even Fe, values could arise from lack of aeration in medium to heavy soils.

0 0

Post a comment