Effect of analytical parameters on the precision of soil zinc extraction methods

Abstract

Fifteen soil samples and four extractants (DTPA, Na₂EDTA, HCl and Mehlich 1) were used to study soil extraction methods for available zinc. Each extractant was studied in three soil: solution ratios (1:2, 1:4 and 1:10) and in three extraction periods in the ratio most frequently used. The zinc extracted by DTPA, Na₂EDTA and HCl was not affected by use of soil: solution ratios 1:2 and 1:4, but the amount extracted increased with the 1:10 ratio. In this relation, the variation coefficients increased. With Mehlich, no definite tendency was observed. The increase of extraction period for DTPA extractant, in 1:2 ratio, had little effect on the amount of zinc extracted and on the precision. As to Na₂EDTA extractant in 1:10 ratio, with the increase of extraction time, both increased. As to HCI and Mehlich, both in 1:4 ratio, the increase in extraction period had no effect on the amount of zinc extracted and no definite effect on the precision. Thus, the use of 1:2 ratio for DTPA and Na₂EDTA and 1:4 ratio for acid extractants is recommended. Concerning the period of extraction, 120 min should be used with DTPA and Na₂EDTA, 15 min with HCl and 5 min with Mehlich.