58 SOIL CONDITIONS AND PLANT GROWTH 



study of the nitrogen nutrition of adult plants is complicated 

 by the difficulty of growing plants under sterile conditions in 

 which the decompositions effected by bacteria are obviated ; 

 much of the earlier work is vitiated by this circumstance. 

 Later work has satisfactorily shown that ammonia is readily 

 assimilated from solutions of ammonium sulphate if the con- 

 centration is not too high ; but even cri per cent, was found 

 injurious by Maze (196). Kriiger(i56) concludes that am- 

 monium sulphate is less beneficial than sodium nitrate for 

 mangolds ; both compounds are equally useful for oats, barley, 

 and mustard, while ammonium sulphate is better for potatoes. 

 Brigham l maintains that maize also thrives better on am- 

 monium sulphate than on sodium nitrate. Hutchinson and 

 Miller (1400) found that peas assimilate nitrates and ammon- 

 ium salts equally well, while wheat showed a decided preference 

 for nitrates. Soderbaum 2 found that the effect varied with 

 the salt : ammonium phosphate was more beneficial than the 

 sulphate, while the chloride was harmful. 



An interesting attempt has been made by Prianichnikow 

 (229^) to elucidate the phenomena of ammonia assimilation by 

 plants. He supposes that the ammonia taken up by the roots 

 is transformed in the plant into as^paragine, which is then con- 

 verted into protein. Some plants, e.g. barley, maize, pumpkin, 

 etc., readily take up ammonia and effect the conversion ; 

 others, such as peas and vetches, do so only in presence of 

 calcium carbonate ; whilst others, such as lupin, will not nor- 

 mally take up ammonia at all. He suggests that this difference 

 is due to the different quantities of carbohydrates at the dis- 

 posal of the plant ; by increasing or diminishing the amount 

 of carbohydrate it is possible to pass from one type of assimi- 

 lation to another. In a state of inanition the power of forming 

 asparagine is lost ; with plentiful supply of carbohydrate, on 

 the other hand, even plants of the lupin type could absorb 

 ammonia and convert it into asparagine. Asparagine can 

 accumulate in the plant without detriment, and can be built 



1 Soil Sci., 1917, 3, 155. 



^Kungl. Landt. Handlingar, 1917, 56, 537-561. 



