In conclusion, our results show that the addition of residues
with a wide C to N ratio strongly decreased the proportion of amino
acid N mineralized. When the same residues were added in combination
with NHþ
4 , the effects were much weaker. These results
suggest that the availability of N relative to C is a dominant factor
determining how soil microorganisms utilize organic N sources.
With 1.4e33% of the added amino acid N mineralized, the
gross N mineralization rate only represented a small and variable
proportion of the N available to soil microorganisms in the short
term.