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say that the word involves two principles, viz. : first, the maintenance 

 of such conditions as will promote the most rapid and beneficial 

 chemical changes in the soil, and second, the conseivation of the 

 proper amount of moisture. 



The chemical changes in a soil are most complex. Formerly the soil 

 was regarded as dead inert matter, totally devoid of life, and until 

 recently there was no suspicion of living organisms within it, except 

 the plants that emerged therefrom. But the up-to-date agriculturist 

 now knows that every well cultivated and fertile soil is penetrated with 

 living beings, in fact a living mass of matter. The mineral part of the 

 soil is to-day regarded as the environment of living organisms, from 

 which the latter may draw a part of its sustenance. While air, water, 

 and mineral matter furnish the materials of plant growth, they must 

 all be digested before they can be assimilated. The mineral matter of 

 every soil must suffer complete disintegration before assimilation, and 

 the only forces so far known capable of accomplishing this work are 

 the secretions of the plants, the vital activity of rootlets, organic acids, 

 and the influence of soil ferments or micro-organisms It is well 

 known that soil ferments are intimately associated with the rootlets of 

 some plants, and hence the leguminous plants are selected for soil 

 improvement. Hundreds of micro-organisms exist in every fertile 

 soil ; some are useful to vegetation, some are noxious. In butter 

 making, it has been found that certain bacteria ripen cream, while 

 others prevent, and the former are now specially prepared on a large 

 scale in the laboratory of the chemist and furnished as bacteria No. 41 

 to the butter makers of the world. So in the soil it has been discovered 

 that organisms favourable to the preparation of plant food are accom- 

 panied by others nearly allied, whose chief function is to destroy the 

 work performed by the former. The object, then of science is to 

 discover some process by which the former may be multiplied and the 

 latter destroyed. Accompanying the ferments already mentioned, are 

 sometimes found others of a pathogenic nature Epidemics among men 

 and animals are frequently due to germs which preserve their vitality 

 in the soil, and passing with plant structure, or into wells or springs, 

 are thus conveyed to animals and men, producing disease. Typhoid 

 fever, lockjaw, charbon, chokra, and by many malaria, now better 

 styled " malaqua," are belitved to be thus propagated The recent 

 spread of charbon throughout the alluvial section of Louisiana, 

 emphasized this fact. Every effort should be made to prevent infect- 

 ing the soil with the germs of any zymotic disease. Cremation of dead 

 carcasses, and the dejecta of living patients, are the best preventives. 

 Health officials in cities have therefore wisely prohibited the use of 

 sewage for agricultural purposes. 



The attention of bacteriologists has been devoted almost exclusively 

 to the study of nitrifying organisms of the soil, and these only in their 

 relation to the collection and preparation of nitrogen as plant food. 

 It is believed, however, by some, that all plant food of every character 

 is the work of micro-organisms within the soil. The relatively high 

 price for nitrogen (or ammonia) in our fertilisers has been the cause of 

 the patient investigation of bacteriologists along the exclusive line of 

 nitrifying and denitrifying germs. Nitrogen is the most costly in- 



