The presence of root-inhibiting substances in cow urine and the cause of urine burn

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Abstract
1. A study has been made of the cause of urine burn in pasture.2. It has been shown that urine burn could occur under dry soil conditions due to the osmotic pressure effects of the urine.3. All seeds present in the urine-affected soil are killed.4. An inhibitor of root growth, to which clover roots are especially sensitive, is present in the urine of cows and sheep.5. This inhibitor, which is not heteroauxin, is acid in character and is destroyed in soil in a few days.6. It is suggested that the inhibitor is an inhibitor-auxin complex, of which the auxin portion might be heteroauxin. The possibility that the inhibitor is an auxin precursor is discussed.7. It is contended that the reduction of clover growth relative to grass growth in a urine patch is not simply the result of shading due to increased grass growth.8. The root inhibitor, the temporarily high pH, the presence of free ammonia, and the high concentration of ammonium ions may be important factors in the reduction of clover growth.