DISTRIBUTION AND PARTIAL CHARACTERIZATION OF ACID HYDROLYZABLE ORGANIC NITROGEN IN 6 NEW-ZEALAND SOILS

Six New Zealand topsoils of widely different origins and properties were subjected to 6m HC1 hydrolysis and the distribution of N fractions and amino acids were determined qualitatively and quantitatively. Of the total-N in the soils studied 83-91%, was hydrolysable with 6m HCl. The largest proportion of the hydrolysable N was α-amino acid N (38- 42%). followed by hydrolysable-unknown N (HUN) (14-24%), and NH4+-N (14-22%). A significant proportion (25-50%) of the HUN fraction was accounted for by the non α-amino acid-N. Oxidative (3% H2O2) hydrolysis released N-phenoxy amino acid-N and possibly N-compounds which were complexed with phenols and sugars. All soils had a similar amino-acid composition with a predominance of acidic amino-acids. © 1979.