Effects of temperature on extractable manganese and distribution of manganese among soil fractions

Abstract

Fertiliser manganese (Mn) does not have good residual value in calcareous soils in southern Australia. The interaction of biotic and abiotic factors determining availability of fertiliser Mn is not well understood. Effects of autoclaving and temperature of moist incubation on DTPA (diethylenetriaminepentaacetic acid)‐extractable Mn and the distribution of Mn among soil fractions was tested in a sandy, calcareous Wangary soil. In the topsoil receiving 10 or 40 mg Mn/kg, higher incubation temperature (26°C) accelerated a decrease in DTPA‐Mn and weakly adsorbed Mn during 0–14 d incubation compared with the lower temperature (15/10°C, 12 h each) regardless of whether soil was autoclaved or not. In a Wangary soil mixed in 1:1 ratio of topsoil to subsoil and supplemented with Mn, higher temperature during soil incubation resulted in higher DTPA‐Mn compared to the lower incubation temperature after 36 d. The decrease in weakly adsorbed Mn with incubation time was mainly due to: (i) Mn fixation by chemisorption on calcite, and (ii) Mn oxidation by soil microflora; the higher the incubation temperature, the quicker the fixation. Autoclaving of the soil fertilised with Mn caused the amounts of Mn in various soil fractions to remain almost constant throughout the 24‐d incubation period regardless of the incubation temperature. The present study indicates that the reduction of Mn availability in soils results when dry non‐autoclaved soil is re‐moistened and incubated at relatively higher temperatures as occurs in the autumn in Mediterranean climates such as that of South Australia.

Notes

Present address: Research Centre for Eco‐environmental Sciences, Chinese Academy of Sciences, Beijing, P.R. China.

Correspondent.