74 [Senate 



of the distribution of inorganic matter been fully recognized. The 

 quantity, however, required for the use of plants is not large. An 

 analysis of three kinds of earth by Prof. Johnston, gave these results: 

 marsh land, . 02 ; salt marsh, . 06 ; and rich pasture, 1.31. Even 

 when in such minute quantities as in the first instance, the amount per 

 acre will be comparatively large, when the quantity demanded by a 

 crop is considered. Suppose this soil containing the least, to be only 

 six inches in depth, and the cubic foot to weigh only 80 lbs., it would 

 contain 3,500 lbs. of lime, or a ton and a half to each acre. By re- 

 ference to a previous table, it will be seen that the four years course 

 of cropping only required 150 lbs. of lime, or reduced the original 

 quantity in the soil to that amount ; consequently this small per cent 

 of lime w^ould be available for some 23 or 24 such courses of cropping, 

 or v/ould last nearly 100 years. But this statement also proves that 

 if the exhaustion of the lime is slow, it is certain, during continued 

 cultivation, and must in some manner or form be restored, or fertility 

 will eventually cease. That such exhaustion has already taken place 

 to a considerable extent, in some of the oldest settled parts of our 

 country, where lime was never abundant, and too little attention has 

 been paid to manuring, can scarcely be doubted. In many instances 

 deep plowing might remedy the evil, as experience proves that in 

 such soils the subsoil usually contains far the greatest per cent of lime, 

 a result to be expected from the fact that lime has always a tendency 

 to sink in the soil — a tendency facilitated by culture. 



The remarks made respecting lime are applicable to any of the in- 

 organic substances in soils, the exhaustion of which, and the time of 

 restoring, may be seen in the tables already given. Thus when the 

 alkalies, such as potash or soda, become deficient in soils, the silicates 

 so indispensable to the formation of plants cannot be produced, and 

 the grasses and grains, to the stems of which in a particular manner 

 they are requisite, cannot be grown in perfection. Cultivation seems 

 to show there is none of the inorganic materials sooner exhausted than 

 potash, especially in soils that are sandy, and there is none of these 

 materials more essential to the growth of many plants, or which is 

 taken up more liberally, as the tables will show. It is for this reason 

 that ashes produce such an excellent effect on most soils, especially 

 when combined with vegetable matter. 



In closing this paper, it is only necessary to add that the object has 

 been more to direct attention to an important part of agriculture, one 



