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Evaluation of Mehlich 3 as a Micronutrient Extractant on Irish Grassland Soils
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2002
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Denis Dominic Brennan (2002). Evaluation of Mehlich 3 as a Micronutrient Extractant on Irish Grassland Soils. M. Sc. Thesis, University of Limerick, Ireland
Abstract
The use of multinutrient extractants has been increasing in recent years, Mehlich 3
(M3) being one that has gained wide acceptance. The objective of this study was to
see how M3 compared with methods currently used in Ireland for Cu, Zn, Mn and Fe
extraction, and to investigate if it could be used to determine available Mo. Samples
from eight mineral soil types, four of sandstone/shale and four of limestone origin
and some organic soils were analysed for the micronutrients Cu, Fe, Mn, Mo and Zn
using M3 and conventional extractants. Herbage samples were taken from specific
mineral soils and analysed for the same range of elements. M3 results showed good
correlation with EDTA and DTPA extractable Cu and Zn, and with easily reducible
Mn, but poor correlation with DTPA extractable Mn and Fe. It was not possible to
measure Mo in the M3 extract. Inclusion of soil properties and interacting elements
in multiple regression models improved the coefficients of determination. Different
relationships between extractants were displayed for mineral and organic soils. All
extractants were equal in their ability to predict micronutrient content of herbage.
Differences between sandstone/shale and limestone soils in relation to herbage
micronutrient content were also found; the better relationships were generally found
on the sandstone/shale. Results are generally in line with published data, but
disagree with those of some studies. M3 is subject to the same shortcomings as
existing extractants, but it’s versatility and range does offer an advantage.