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.

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In the course of investigations into the changes in nitrogenous constituents of herbivorous urine when voided on pasture (Doak, 1952), opportunity was taken to study in greater detail the phenomenon of urine burn. This normally occurs in hot weather when soil moisture approaches the wilting point, and it was noted that the soil within the patch remained bare for relatively long periods. The complete lack of seedling growth, either of pasture species or of weeds, was particularly noticeable, and the obvious conclusion was that urine had caused the death of all seeds in the top layer of the soil. An investigation was therefore started on the effect of seedling growth and on the possibility that urine contains substances with phytotoxic properties. EXPERIMENTALMaterials Short rotation ryegrass, white clover and subterranean clover were used as test plants in preliminary work. As the clovers proved to be considerably more sensitive than the grass, and as there was no noticeable difference in the sensitivity of the clovers, most of the testing was carried out vising subterranean clover. As pointed out by Greenwood (private communication), this plant offers the advantages of easier handling and less genetical variation. The seed used was screened closely for size and was selected for uniformity at germination when the radicles were just visible.A bulk supply of cow urine was collected and stored in 1 gal. containers at -10° C. This urine contained 0-62 % total nitrogen, of which 83 % was present as urea.In the early part of the work the urine •was ether extracted at pH 7-6 (alkaline ether extract), then ac idified to pH 2 • 9 with hydrochloric acid and further extracted with ether (acid-ether extract). Peroxidefree ether was used throughout. (Extraction at pH 7-6 was omitted after it was shown that this extract showed no inhibitory properties.) To obtain complete extraction it was necessary to break the gelatinous emulsion by centrifugation.Before application of the extracts ether was removed and the residue made up to the required volume with half strength Hoagland's nutrient solution. Apart from the nutrient effect the Hoagland solution would tend to minimize any possible osmotic effects of the urino extracts.The effect of osmotic pressure of urine

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