Plant capture of free amino acids is maximized under high soil amino acid concentrations

Free amino acids (AAʹs) represent a significant source of available N for some plants and soil microorganisms. It can be expected, however, that significant competition will exist between plants and microorganisms for this organic N resource. Our study indicated that microbial capture and utilization of glycine was very rapid at a range of soil solution concentrations (0.1 μM to 10 mM) indicating that significant competition will exist between roots and soil microorganisms. Plant capture of free AAʹs was maximal at high soil solution concentrations where microbial utilization was slowest. Our results suggest that plant capture of soil dissolved organic N may primarily occur in organic rich patches in soil where concentrations of free AAʹs are high.