[licpn'nted from the Journal of Agricidtaral tScience, Vul. HI. I'jirt 11. J 

 [All liiijhts reserved.] 



DIIIECT ASSIMILATION OF AMMONIUM SALTS 



BY PLANTS. 



By H. B. HUTCHINSON, Pii.D., and N. H. J. MILLER. 

 Rotharasted Experiineitt Station. 



It has recently been shown' that the soil of some of the Rothanisted 

 Grass Plots which have I'eceived ammonium salts for many years in 

 succession has become distinctly acid and that, consequently, nitrifying 

 organisms have become greatly reduced in numbers. Nitrification is 

 limited to portions of soil directly in contact with the few particles of 

 calcium carbonate still remaining in the soil. It is evident therefore 

 that more or less of the nitrogen assimilated by the grasses must be in 

 a form, or in forms, other than nitrate — probably mainly as ammonium 

 salt. In view of these results it seemed desirable to obtain additional 

 evidence of direct assimilation of ammonium salts by plants. 



The question possesses a further interest in the case of leguminous 

 plants, since whilst non-leguminous crops (whether able to assimilate 

 ammonia or not) undoubtedly take up, under normal conditions, most 

 of their nitrogen in the form of niti'ates, we have no knowledge of tlie 

 form of nitrogen appropriated by leguminous plants from their root 

 nodules. 



In 1890, Loew- showed that platinum black in presence of alkali 

 produces ammonium nitrite from nitrogen and water, and suggested 

 that assimilation of free nitrogen is accomplished in a similar manner. 

 The examination by one of us, in 1890, of numerous fresh nodules 

 showed almost invariably an alkaline reaction, sometimes very marked. 

 When this view, assigning an indirect role to the nodule organism — the 

 production of suitable physical and chemical conditions for the union 

 of nitrogen with the elements of water — was put forward, fixation of 

 nitrogen apart from the nodules had not yet been observed. Recently 

 Loew and Aso^ have suggested that ammonium nitrite is the first 



1 Proc. Roy. Soc. 1908, B. 80, 196. ^ iJer. 1890, 23, 1447. 



3 Bull. Coll. Agric. Tokyo, 1908, 7, 567. 

 Journ. of Agric. Sci. in 13 



