. 1989. Decomposition of wheat straw and stabilization of microbial producrs. Can. J. Soil This research examined the effects of soil environment on the decomposition of cereal crop residues and stabilization of microbial products in the field. Microplots at semiarid and subhumid field sites were amendedwith rac-. rsN-labelled whlat straw and with rac-labelled glucose plus rsN-labelled NH4NO3 and the fate of the residual C and N was monitored over l0 yr. Mineralization of C and N derived from wheat straw was greater at the site in the more moist environment in the short term (2 yr). In the long term (up to l0 yr), however, the residual C and N at this site decayed at a slightly slower rate, providing evidence of stabilization of organic material in chemically resistant forms, as compared to possible physical protection in the semi-arid clay-textured soil.The total recovery of labelled N was22.5-24% inthe harvested crops with 13.4-167o remaining in the surface soil by the end of the study. Mineralized labelled organic N was used with an efficiency ranging from 32 to 5lVo. However, after summer fallow the crop apparently used mineralized labelled N with an efficiency of only 7 Vo. This study showed that moistness of the soil environment has a considerable effect on residue decomposition. Stabilization of humic material derived from residues relates more to the recalcitrance of microbial products and their interactions with soil mineral colloids than to the nature of the original residue.Key words: Mineralization rates, crop residues, microbial turnover, chemical recal-

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A method with the combined advantages of soil particle washing, selective inhibitors, and an indicator substrate was developed to isolate saprophytic basidiomycetes from soil. Organic particles were washed from soil and plated on a medium containing lignin, guaiacol, and benomyl, which reduced mold growth and allowed detection of basidiomycetes producing laccase or peroxidase. The 64 soil samples yielded 67 basidiomycete isolates, representing 51 groups on the basis of morphology and physiology. This method should facilitate investigations into the biodiversity of soil basidiomycetes and yield organisms that are useful in bioremediation of soils contaminated with pesticides or other recalcitrant aromatic compounds.

. Can. J. Soil Sci. 61: 373-385. The effect of labile inorganic phosphate (Pi) status of the soil on the decomposition of added cellulose and on the immobilization, mineralization, and redistribution of.native and addcd P in soils was studiecl in a grcenhousc incubation experiment. Cellulose was addcd at 765 pg C.gr soil with and without P (9 pg'g' soil) every 30 days under adequatc N, H2O, and constant tempreature to two soils of different available P status.Lacli of P eventually slowed down decomposition of added C, but this effect was partially compensated for by increased mineralization of organic P (P.) fbrms. Added P was re