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SCIENTIFIC MANUAL. 



89 



he must ascertain, either by analysis or experiment, or by 

 both conjointly, the chemical constituents of his soil, in or- 

 der that he may know to what crops it is best adapted, and 

 what elements of plant-food need to be artificially supplied. 



With a knowledge of the physical and chemical require- 

 ments of the different cnltivated crops, and a familiarity 

 with the physical character and chemical composition of 

 the soil, the farmer may, by supplying the deficiences of 

 the latter, fulfill the requirements of the former. 



Phosphoric acid and potash are the first mineral ingredi- 

 ents exhausted from cultivated soils, and generally the only 

 ones which need artificial application. These, with nitro- 

 gen, form the valuable part of most commercial fertilizers. 

 Many soils are naturally deficient in lime, and it is often 

 leached through the surface on others, rendering its appli- 

 cation not only desirable but necessary. Soda and mag- 

 nesia are beneficial, as special manures, to particular plants. 



Plants differ materially in the kind and quantity of min- 

 eral matter required for their production, and thus are ex- 

 haustive of the soil in different degrees. The following 

 analysis of tobacco, cotton fibre, Cotton seed, and wheat 

 showing the amount of different mineral matters contained 

 in 1,000 parts of each, will illustrate this fact : 



An inspection of the foregoing analyses develops im- 

 portant facts, which the farmer may use to his advantage. 



1st. They show the principal mineral elements required 

 by each plant for the production of those parts which are 

 removed from the soil, and which, if not already present 

 in the soil, must be supplied by the farmer. 



