4H the land we live on 



An increase of nitrogen in soil is derived, as already 

 mentioned, from the small amounts of nitrogen compounds 

 dissolved in the rain water. 



As shown by the now historical researches of Hell- 

 riegal, leguminous plants make direct use of the atmos- 

 pheric nitrogen by ths aid of micro-organisms, living in 

 the root nodules, and green-manuring, with leguminous 

 crops, can therefore to some extent supersede the direct 

 application of nitrogenous manures. Bacterial cultures 

 under the name of " Nitragin," to be added to the soil or 

 for the direct treatment of the seed itself, to encourage the 

 activity of the nitro-bacteria, were prepared by !Nobbe, 

 of Tharand, and Hiltner, in 1896, but did not prove a 

 great success. Such cultures have been improved by G. 

 Moore, of the U.S. Department of Agriculture. 



Another gain of nitrogen is finally obtained by the 

 action of bacteria and micro-organisms living free in the 

 soil, which are capable of assimilating atmospheric nitrogen. 

 Winogradsky has already years ago proved such assimi- 

 lation of nitrogen by certain forms of Clostridium ; Beijer- 

 inck, Heinze, and others, by certain blue-green algae, 

 Cyanopkyceae. 



Of more recent date are the investigations of Kriiger, 

 Schneidewind, Maze, Gerloch, Vogel, Heinze, and others, 

 proving fixation of atmospheric nitrogen by so-called 

 Azoto-bacteria. The presence of these bacterial forms 

 was detected in the soils of cultivated fields and of meadows, 

 in sand of dunes, and also in seawater. Azoto-bacteria 

 require for their growth not only certain amounts of easily 

 available mineral substances, chiefly phosphoric acid and 

 potash salts, but also organic compounds for the supply 

 of carbon, as these low forms of life cannot assimilate 

 carbonic acid. These compounds are furnished by the 

 higher plants, and by the decay of vegetable matters. 

 The bacteria further require suitable temperature, 

 mositure, and finally, plenty of air, so that they thrive 

 best in loose, moist, deeply cultivated soil. 



The farmer has it, therefore, in his own hands to 

 improve the nitrogen contents of his land by encouraging 

 the growth of these organisms by thorough cultivation. 



Dr. R. Greig- Smith, the Macleay Bacteriologist of 

 the Linnean Society of- New South Wales, in his studies 



