390 MISCELLANEOUS FARM SUBJECTS 



Organic Constitution. In the decay of the organic matter 

 through fermentation or otherwise, not one but many intermediate 

 bodies are formed, some of which may be beneficial and others may 

 be more or less deleterious to crops and each having different charac- 

 teristic properties and reactions with mineral salts. In other words, 

 if we look upon the cultivation of the soil as a method to promote 

 fermentation for the purpose of facilitating certain necessary organic 

 changes and of rendering the soil suitable and sanitary for a sub- 

 sequent crop, we may expect an influence of climate on fertilizer ef- 

 fects, as we would have different intermediate decomposition products 

 formed in the breaking down of the organic matter under different 

 moisture and temperature conditions. 



Different combinations of the different plant-food constituents 

 have different effects upon the crop. For example, the different salts 

 of potassium, the different forms of nitrogen in mineral salts and in 

 organic material, and the different forms of phosphorus have dif- 

 ferent effects on different soils, with different crops, and in different 

 seasons. It is easy to show that it is the substance rather than the ele- 

 ment, for the same plant-food element may be in compounds which 

 are more or less beneficial or in other compounds which produce 

 very unfavorable conditions in the soil, rendering them more toxic 

 for plant growth. Such in a broad way is the present state of knowl- 

 edge in regard to the principles of fertilizer effects on soil fertility. 



The Bureau of Soils has made a thorough comparative investiga- 

 tion of the fertilizer and manurial requirements of several hundred 

 samples of soils from various parts of the United States, under as 

 nearly as possible the same climatic conditions. These investiga- 

 tions show that fertilizers are relatively more effective on light than 

 on heavy soils ; also that they give, as would be expected, the greatest 

 relative effect on poor soils rather than on rich soils, when both are' 

 put in good physical condition. 



For the greater number of soils the most efficient fertilizers of 

 the future will be of organic rather than mineral origin, provided 

 that when such a substance is found it can be obtained in sufficient 

 quantity and a sufficiently low cost and be at the same time less bulky 

 to ship than stable manure. 



There is a general feeling, although this does not seem to be 

 borne out in practice, that both nitrate of soda and potash are more 

 efficient in moderately cool climates and phosphates and organic 

 nitrogen in warmer climates. The Bureau of Soils' comparative 

 study under similar climatic conditions indicates that on the soils of 

 the North Central States manure is about three times as efficient as 

 mineral fertilizers. 



Effects on Different Soils. In the soils of the Atlantic and Gulf 

 States manure and green manure are about equally as effective as 

 mineral fertilizers. It must not be forgotten that on certain soils, 

 either under field conditions or in pots, manure appears to be dele- 

 terious and on some soils mineral fertilizers likewise appear to be de- 

 leterious, although the cases where either of these extreme results 

 occur are very rare. 



