FERTILIZERS 119 



wards per ton, sulfate about forty -eight dollars, 

 dissolved boneblack about twenty -four dollars, 

 ground bone about thirty dollars, kainit about 

 thirteen dollars, and nitrate of soda about two and 

 one-fourth cents per pound. These prices vary, of 

 course, with the composition or mechanical condi- 

 tion of the materials. The average composition 

 of unleached wood ashes in the market is about 

 as follows: Potash, 5.25 per cent; phosphoric acid, 

 1.70 per cent; lime, 34 per cent; magnesia, 3.40 

 per cent. The average composition of kainit is 

 13.54 per cent potash, 1.15 per cent lime. The 

 composition of sylvinit (which is said to be known 

 as sulfate of potash in some quarters) is about 

 16 per cent of potash, in the form of both 

 muriate and sulfate, mostly the former. The 

 fact that the soil itself is the greatest storehouse 

 of plant -food is shown by the following average 

 of thirty -five analyses of the total content of the 

 first eight inches of surface soils, per acre: 3,521 

 pounds of nitrogen, 4,400 pounds of phosphoric 

 acid, 19,836 pounds of potash. Much of this is 

 unavailable, but the good tillage and green manur- 

 ing which have been recommended tend to un- 

 lock it, 



