Joint International Conference on Long-term Experiments ...

micronutrient soil tests for many years. The disadvantage of this method is to solve
such Zn and Cu forms which are not available for plants, and unsuitable for calcareous
soils.
One of the major advances in micronutrient soil testing has been the development
of extracting solutions that contain DTPA and EDTA. Chelates reduce the activity of
free metal ionsin solution through the formation of soluble metal-chelate complexes.
Free ion concentration in the soil solution is replenished from solid phases in response
to this micronutrient chelation. The quantity of micronutrient extracted by a chelate
reflects both the initial concentration in the soil solution (intensity factor) and the ability
of the soil to maintain this concentration (capacity factor), (Viets and Lindsay, 1973).
Therefore, chelating agents may simulate nutrient removal by plant roots and the
replenishment of the micronutrient from labile phases in the soil.
In this study we focus on the first step i.e. laboratory test of the extractant
selection. We chose KCl-EDTA, Lakanen Erviö extractants as official Hungarian
methods and DTPA-CaCl2 as a frequently studied extractant word-wide. Molnáros et al.
have already made similar investigations on west Hungarian soils, but they have not
involved DTPA- CaCl2 in their studies.
Our aim was to examine the relationship among Cu and Zn extracted by the three
extractants on 27 soil samples with different soil properties.
MATERIALS AND METHODS
Charactaristics of the applied extractants are represented in Table 1. 27 soil samples
from Soil Information and Monitoring System (SIMS) of Hungary were used. The soil
samples were collected from Hajdú-Bihar and Szabolcs-Szatmár-Bereg counties. The
soils varied greatly in their physical and chemical properties and included sand, loam
and clay as well. Table 2 summarizes the most important soil properties.
Extactant
KCl-EDTA
DTPA-CaCL2
Lakanen
Erviö (LE)
Table 1. Some physical and chemical characteristics of soils
Extractant
composition
0.05 M EDTA
(as Komplexon III)
0.1 M KCl
0.005 M DTPA
0.1 M CaCl2
0.1 M TEA
0.02 M EDTA
(as Komplexon II)
0.5 M NH4OAc
0.5 M CH3COOH
Soil
extractant
ratio
Shaking
time
(min)
pH Reference
1:2 120 4.36 MSZ 20135
1:2 120 7.2
Lindsay et al.
1978
1:10 0 4.65 MSZ 20135
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