Phosphate retention in the organic horizon of a stagnopodzol soil

In a recent study of the impact of clear felling on element cycling in sitka spruce plantations* a large flux of phosphate from the felling brash into the soil was observed following felling. The phosphate was, however, efficiently retained in the 0 and E horizons of the ferric stagnopodzol soil (Avery 1980)13, with very little reaching the Bs horizon. The retention of the phosphate in the upper soil could have been due to incorporation into the microbial biomass or to physicc-chemical adsorption onto soil surfaces, or to a combination of both mechanisms. This paper reports the results of a preliminary study designed to assess the relative importance of the two mechanisms in the retention of phosphate in the 0 horizon.