NITROGEN FORMS IN 1-YEAR-OLD TO 7-YEAR-OLD OPENCAST LIGNITE MINE SOILS

We studied the distribution of different forms of N in very young (0- to 7-year-old) soils from the Meirama lignite mine in northwest Spain. Total N increased rapidly with soil age, largely in the humic acid-as sociated fraction. Acid hydrolysis indicated that amino acid N and a h ydrolysable unknown form of N increased with soil age. The fractionati on reported by Bettany et al. (1980) indicated that alkali/pyrophospha te-extractable humus increased with soil age. All these data suggest t hat there is rapid stabilization of organic N during the first few yea rs of evolution of these mine soils, to the extent that distribution o f N forms in the 7-year-old soil is very similar to that in native soi ls.