
%0 Journal Article
%A Roberts, FJ 
%T The annual pattern of potassium release from organic matter in sandy soils of south-west Australia
%J Soil Research
%D 1968/12/01
%V 6
%N 2
%P 193-202
%K 
%R https://doi.org/10.1071/SR9680193
%U https://www.publish.csiro.au/paper/SR9680193 
%X Regular field sampling of the 0-3 in. horizon of a sandy soil disclosed an annual pattern of potassium release from the organic matter fraction and retention by the microbial population. The exchangeable + soil-solution potassium content KE+S reached a maximum in autumn (March) at a time when microbial potassium KM and non-exchangeable potassium associated with organic matter KOM were at minimum levels. In soils containing 4% or more of organic matter the KM and KOM categories were important sources of supply of potassium entering the KE+S form. Release of potassium was rapid at temperatures of 40°C and above, but was much slower at lower temperatures. Temperatures in the surface horizon of soils in parts of south-west Australia often exceeded 40°C during the summer period; at these temperatures release occurred more readily in wet soils than in dry soils. Two slight peaks in microbial retention of potassium occurred during early winter (April-May) and spring (October-November). The significance of the observed fluctuations is discussed in relation to leaching and plant uptake of potassium. 
