Some chemical changes in the nitrogenous constituents of urine when voided on pasture

Abstract

1. The chemical changes which take place in a urine patch have been studied using urine from wethers and to a small extent from cows.2. The sizes of individual urine patches vary considerably, depending mainly on the volume of the urination. The average from wethers is about 45 sq.in.3. The volume of urine per wether per day averages 2880 ml. with a nitrogen content of 0·92%, of which about 75% was in the form of urea; 4·1% as allantoin; 2·6% as hippuric acid; 1·5% as creatine-creatinine; and 12·4% as amino-nitrogen.4. Improved herbage growth results in twice the area actually wetted with urine. The total area affected averaged 100 sq.in.5. The probable area wetted with urine from cow urinations was about 650 sq.in. with a further 200 sq.in. affected indirectly.6. With wethers the average rate of nitrogen application on a urine patch amounts to 432 lb. of nitrogen per acre.7. The rate of hydrolysis of urea in laboratory experiments is affected by temperature and is increased by small amounts of hippuric acid but not by the other urinary constituents tried. The hydrolysis rate is greater at soil moisture content of 24% than at higher moisture levels.8. Urea hydrolysis in soil (both in laboratory and in the field) is accompanied by pronounced increase in pH (up to pH 9·2 with urea equivalent to that applied to a urine patch).9. The rate of nitrification is greatly affected by the pH changes. At pH values in excess of 8 nitrites accumulate and nitrate formation is retarded.10. Heteroauxin and allantoin were both found to stimulate nitrification in laboratory experiments when used at levels found in urine. Other urinary constituents were without effect.11. The hold up of urine on leaf surfaces of pastures was shown to amount to as much as 12·5% of the green weight of herbage.12. Ammonia in considerable amounts may be lost to the air both from herbage and from soil.13. Field experiments are in complete agreement with laboratory experiments and no essential difference of wether and cow urine was noticed.14. The fate of the nitrogenous constituents is briefly considered and shown schematically.