354 EXPERIMENT STATION RECORD. 



cui., iiiid tliey frequently exceed this depth, it is estimated tliat the soil 

 of 1 hectare (within the reach of the roots of plants) weighs about 4,000 

 tons and contains 4,000 to 8,000 kg. of combined nitrogen. When we 

 remember that good cro])S of beets or of gram require only from 100 to 

 120 kg. of nitrogen, it is a matter of surprise that these crops will not 

 thrive unless there is annually added to this enormous stock of com- 

 bined nitrogen 150 to 1*00 kg. of nitrate of soda containing from 22 to 

 30 kg. of nitrogen. 



It is clear that tlie nitrogen is held in the soil in stable (Combinations 

 which resist the action of air and water and do not furnish sutticient 

 food to plants at certain stages of growth when they most need it. 

 Furthermore, the conditions of culture are very different from those 

 which obtain in connection with spontaneous vegetation. The flora of 

 a meadow, for instance, is composed of different species wliich arrive at 

 maturity at successive periods. It is entirely different, however, in ordi- 

 nary field culture. lu the latter there is grown on the soil a large num- 

 ber of plants of the same species seeded at the same time and passing 

 through different i)hases of growth together and all having the same 

 needs at the same time. The transformation of the organic nitro- 

 genous material of the soil is not sufficiently rapid or is not sufficiently 

 complete in time to supply their needs, and hence the use of nitro- 

 genous fertilizers is rendered necessary. This is more particularly 

 necessary because we do not know how to hasten the transformation 

 of the nitrogen of humus during spring and early summer into those 

 forms which are assimilated and utilized by plants. 



Under what influences are these transformations brought about? To 

 what agencies are they due? Is it possible by means of these agencies 

 to utilize the enormous reserves of combined nitrogen which humus 

 soils contain? These are the questions which it is proposed to discuss 

 in this article. 



ASSIMILATKIN OF A:\rMONIA — TRANSFORMATION OP THE NITROGEN OF 

 IIUMI'S INTO AMMONIA. 



According to the work of Boussingault and Ville it would appear 

 that nitrogen is not assimilated in the form of ammonia. The numerous 

 experiments of Schattenmann in Alsace, of Kuhlmann in the Dej)art- 

 ment of Nord, and of Lawes and Gilbert at Rotharasted, England, have 

 demonstrated the effectiveness of ammonia salts as fertilizers, liecent 

 observations have rendered untenable the opinion, based on the ready 

 assimilability of nitrates and the rapid nitrification of ammonia in the 

 soil, and luild until within a few years by certain agriculturists, that 

 plants utilize ammonia only after its oxidation and transformation to 

 nitrates. Miintz, of the Agricultural Institute of Pans, has demon- 

 strated the falsity of this view. He grew plants in a soil deprived of 

 nitrates by prolonged" leaching and freed from nitrifying, ferments by 

 the action of heat. He also took special precautions to prevent the 



