Recovery and vertical distribution of 15N labelled fertilizer nitrogen in forest soil

Abstract

Laterally isolated micro-plots were used for studying the recovery and vertical distribution of various sources of 1%-labelled fertilizer nitrogen in the soil beneath a 90 years' old stand of Scots pine (Pinus silvestris L.). The fate of the added nitrogen was followed by sampling and analvsing the field layer vegetation, litter and soil after different time intervals during the growing season 1968 (4 times) and also in spring 1969 (once). Of the calcium nitrate, ammonium sulphate and urea-N added, the amounts recovered at the end of the experiment (i.e. after 12 months' exposure) were 23, 63 and 76 per cent, respectively. Less than ten per cent of the recovered N was in inorganic form. Urea-N showed the lowest mobility of the fertilizers applied, and tended to accumulate in the litter and humus layers.