COMPETITION FOR NITROGEN DURING MINERALIZATION OF PLANT RESIDUES IN SOIL: MICROBIAL RESPONSE TO C AND N AVAILABILITY

were placed into soil as separate layers, negative effect of plant roots on microbial growth was observed. ‘I’he depression effect occurred predominantly in N-poor plant residue layers, which indicated that microbial growth can be limited by N availability in such microsites in soil. More energy substrates were available in the planted straw layer, as indicated by a significantly higher N immobilization poten-tial in the planted soil compared with that in the unplanted soil. However, in the N-rich sites, plant roots stimulated N mineralization during 1 wk incubation of soil slurries. Microbial response to initial growth conditions, including C and N availabihty, are also discussed. 0 1997 Elsevier Science Lt