568 SELECTIONS FROM ADDRESSES. 



The connection between the soil and the plant being thus 

 made out so clearly, the question of fertility or barrenness 

 becomes, as a general rule, very simple, and one which the j 

 chemist can determine with great certainty. The valuable 

 practical conclusions which we are able in various ways to 

 draw from this knowledge are exceedingly numerous and im- 

 portant. 



In the first place we are able to supply deficiencies, and to 

 remedy defects, much more readily than ever before. Let us 

 suppose a farmer to have some land which is deficient in lime, 

 one of the substances absolutely necessary in a fertile soil. He 

 adds some common farm yard manure ; this it is true contains 

 all that is needful in the soil, and partly supplies its deficien- 

 cies, but in the present case there is a special defect, and iu 

 order to supply the soil properly, a large quantity of special 

 manure should be added ; now of the yard manure each ton 

 will contain perhaps fifteen or twenty pounds of lime — to fur- 

 nish half a ton of lime then, it would be necessary to add no 

 less than fifty tons of yard manure to each acre. But it is not 

 at all uncommon, to apply lime at the rate of several tons per 

 acre ; and this is no more than a proper quantity when entire 

 deficiency exists. It is then quite plain that a heavy, and even 

 an excessive addition of common manure, will not properly 

 supply a special deficiency. Thus a knowledge of the com- 

 position of his soil, would save the farmer not only expense, 

 but time and labor, and this to a very considerable extent. 



Cases of this kind might be multiplied : it not unfrequently 

 happens that three or four bushels per acre of sulphate of lime, 

 that is, the common plaster of paris, produces more efiect than 

 tons of other manures, and will continue the land in a fertile 

 condition for some years. This too is a case of special de- 

 ficiency. 



There is no more common want in our long cultivated soils, 

 especially where much grain has been grown, than of a sub- 

 stance called phosphoric acid. You may not many of yoji know 

 what this is, nor is it necessary for our purpose that you should; 

 suffice it to say that it exists more largely than any other sub- 

 stance in the ash of grain, there being comparatively little in 



