APPENDIX I 



SOIL FERTILITY 



WITHOUT attempting to go into the subject of soil fertility to 

 any great extent, the authors have thought that a brief discussion 

 of the subject, giving some of the underlying principles, would be 

 helpful to the farmer. The field is such a large one, and the theories 

 advanced are so varied and conflicting, that the practical farmer 

 is at a loss to know what to do, and as a consequence does nothing. 

 The fertility needs of soils may be determined in three ways: (1) 

 by chemical analysis, by which the amount of plant food may be 

 determined, (2) by pot culture experiments in greenhouses under 

 almost perfect conditions, and (3) by actual field tests, where plant 

 foods of different kinds may be applied and the results compared 

 with those of an equal area of the untreated soil growing the same 

 crop. 



Permanent Agriculture. Agriculture is usually considered a 

 permanent industry, but it is no more permanent than the natural 

 soil itself. If the fertility of the natural soil is inexhaustible, then 

 agriculture is a fixed industry and likewise those industries, com- 

 merce, manufacturing, and mining, which depend so largely upon 

 agriculture. If history tells us anything about agriculture it is 

 this: that it is not permanent, that nations have fallen because the 

 agriculture upon which their civilization depended had failed. 



Are Soils Inexhaustible? The productiveness of soils depends 

 upon the amounts and kinds of plant food elements they contain, 

 the favorable conditions for plant growth that they offer, and the 

 friendly bacteria present. Chemical analyses show that plants 

 contain certain mineral elements which they obtain from the soil. 

 Analyses show further that soils contain these elements in limited 

 quantities, and it requires no great amount of mathematical knowl- 

 edge to see that if plants take even small amounts of these elements 

 from this limited supply, reduction and final exhaustion are sure 

 to follow unless the necessary elements are added by the farmer. 



Complete exhaustion of plant food is not necessary to render a 

 soil unproductive. If the soil presents adverse conditions to the 

 plant, either through lack or excess of water, poor aeration, or bad 

 physical condition, or if the proper bacteria are not present, or, 



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