Has Urea any Poisonous Action on Phaenogams? 



BV 

 S. Sawa. 



Sometimes urine is applied as manure before its urea is 

 completely split up by bacterial action into ammonia and 

 carbonic acid. But while the ammonia can be absorbed in the 

 soil and thus becomes only gradually accessible to the roots, 

 a poisonous action by a too high concentration of ammonia being 

 thus avoided, 1 the urea is not absorbed in the soil as Kellner 

 has shown. It might be supposed, however, that urea could act 

 injuriously and I have therefore made an experiment with young 

 onion plants in order to test this point. Thus far it has been 

 generally assumed that urea would be a good source of nitrogen 

 for the phaenogams, but some objections may be raised against 

 the tests thus far made. 2 



On April 22nd two plants were placed in Knap's solution 

 with an addition of 0.5 p.m. urea and also two control plants 

 without this addition. These plants were kept over five weeks, 

 in a room near the window at 15 — l8°C. The solutions were 

 twice renewed. A start towards the formation of flowers was 

 made by each plant, but only in the one to which urea had 

 been applied was a full flower developed, in the other three 

 plants there being no further development. 



Gradually new branches developed with the four plants, 

 but much better with the control plants than with those in the 

 urea solution ; soon afterwards, however, the old leaves com- 

 menced to die off from the tip downward. Finally on the 30th 

 of May, the parts still living were measured. The results may 

 be seen in the following table : 



1 On the poisonous action of ammonium carbonate in water culture, see Bui. of the 

 Coll. of Agr., Tokyo, Vol. III., No. 3. 



2 Comp. JIampe, Landw. Versuchs. St. Vol. 10. Also Thompson, Centr. f. Agr. 

 Chem. Aug. 1901 ; the urea solution being permitted to act for only 3—5 hours each day. 



