Studies on composts prepared from waste materials II the fractionation of organic nitrogen

1. The effect of acid concentration and time of hydrolysis on the amount of nitrogen dissolved from sewage sludge and composts was investigated. The amounts of α‐amino‐nitrogen and ammonia‐nitrogen in solution were determined.

2. The amount of total nitrogen dissolved by 22% (w/v) hydrochloric acid in 16 hours at 100° was 83‐88%, and this did not increase appreciably in 48 hours.

3. α‐Amino‐nitrogen in this solution reached a maximum in 16 hours and then decreased; ammonia‐nitrogen continued to increase up to 48 hours. The increase in ammonia was attributed to deamination.

4. The α‐amino‐nitrogen and amide‐nitrogen contents of composts from wheat straw and sewage sludge, and wheat straw and ammonium sulphate, and the solubility of the nitrogen in 2% and 22% (w/v) hydrochloric acid were determined at different stages of decomposition.

5. The changes in the percentage of total nitrogen present as α‐amino‐nitrogen and amide‐nitrogen were greatest during the first few weeks of composting.

6. The percentage composition of the insoluble organic nitrogen present, defined as the nitrogen not soluble in cold o.IN‐hydrochloric acid, appeared to be almost independent after 3 months' decomposition of the initial source of nitrogen used in composting.