18 ORGANIC CONSTITUENTS OF SOILS. 



influences such as are at least partially illustrated by the experimental 

 results cited here. Yi'e believe that these additional note particu- 

 larly that I say additional actions explain more fully the function 

 of fertilizers in agriculture. From the former view the application 

 of fertilizers would be restricted to poor and so-called exhausted 

 soils and poor systems of agriculture; from the latter viewpoint fer- 

 tilizers are indicated as well for fertile as for infertile soils, as an 

 adjunct to successful farming, and for bringing the soil to its highest 

 capacity of crop production. 



The action of fertilizers on soils is a much contested question, but 

 the weight of evidence is against the assumption that their effect 

 is due altogether to the increase of plant food as such. If so simple 

 an explanation were the true one, nearly a century of investigation 

 of this problem by scientists of all civilized nations would surely have 

 produced greater unanimity of opinion than now exists in regard to 

 fertilizer practice. Thoughtful investigators everywhere are finding 

 that fertilizer salts influence many factors which contribute toward 

 plant production besides the direct nutrient factor for the plant. It 

 is this additional influence of fertilizers which makes them doubly 

 effective when rightly used and inefficient when improperly used. 

 To this influence of fertilizers on soil and biological conditions is due 

 their capriciousness when applied on the theory of lacking plant food. 

 Any study which throws further light upon the mooted question is 

 of direct help toward reaching that view of soil fertility and soil 

 fertilization which will eventually result in a more definite, more 

 rational, and more remunerative fertilizer practice than in the past, 

 and thus bring about the more extensive use of f ertilizers in agriculture. 



Approved : 



JAMES WILSON, 



Secretary of Agriculture. 

 Washington, D. C., October 23, 1912. 



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