ISSN:
1573-5036
Keywords:
Acid soils
;
Chelating agents
;
Cu
;
DTPA
;
EDTA
;
Fe
;
Mn
;
Zn
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary The practice of buffering the pH of the extracting solution to neutrality or above when estimating available micronutrients with the 0.005M DTPA and 0.04M EDTA soil tests was studied using a number of soil samples from a liming experiment. Generally the soil constituted a better buffer system than the commonly used buffers (e. g. ammonium hydroxide, 1M ammonium acetate or 0.1M TEA). Raising the pH of extraction above that of the soil generally altered the quantitites of micronutrients extracted with 0.005M DTPA but had little effect on those extracted with 0.04M EDTA. In further experiments, using a number of acid soils, the effect of adjusting the pH of the extraction system, over the range 4.5 to 7.5, on the quantities of micronutrients extracted by 0.005M or 0.04M DTPA and EDTA was examined. For some soil samples the use of the 0.005M concentration of chalate resulted in a marked peak in extractable Mn, and to a lesser extent Cu, in the range 5 to 6. This was attributed to secondary interactions among cations, Al3+ and Fe3+ at low pH and added Ca2+ at high pH, affecting the quantities of micronutrients being extracted. For a sample of peat, the quantities of Zn, Cu and Mn extracted with 0.005M DTPA or EDTA behaved irregularly as the pH was increased. The strong complexing ability of organic matter may have contributed to such trends. Raising the concentration of the chelate from 0.005M to 0.04M overcame much of the pH-dependent variability in micronutrient extractability since the quantities extracted from all soils generally decreased with increasing pH. It was concluded that the 0.005M DTPA soil test is not suitable for use over a wide range of soil pH values; particularly where the availability of Mn and Cu are important.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02178746
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