SOIL A^D ITS PREPARATION. 11 



two thousand six hundred and forty cubic inches per 

 acre of available soil, with its mineral ingredients, and 

 constantly increasing capacity of gathering, retaining, 

 and supplying plant food. The conditions of quality of 

 soil and climate being the same, the productiveness of 

 soils must be in proportion to its mass. Sir J. B. Lawes 

 found five thousand seven hundred pounds of nitrogen 

 per acre in the first nine inches of his soil. The Russian 

 black lands, which are held to be the richest in the 

 world, have, according to Prof. Schmidt, within three feet 

 of the surface, from forty thousand to forty-four thousand 

 pounds of nitrogen. Several analyses of Boussingault 

 showed from twenty-five thousand to thirty-two thousand 

 pounds per acre beneath the surface, and a soil analyzed 

 by Prof. Voelcker, in 1868, showed eight thousand four 

 hundred and twenty-five pounds per acre. The practice 

 of deep plowing will depend upon circumstances; a good, 

 though shallow mould, or other soil, resting upon a 

 sticky, clay subsoil, would not be benefited by being at once 

 broken up deeply, bringing large, hard lumps of unfertile 

 clay to the surface, and deteriorating the physical quality 

 of the top-soil. 



DRAINAGE. 



Drainage, more especially underdrainage, renders a 

 clay subsoil, when moved by the plow, more suscepti- 

 ble to pulverization, and in such case a thorough 

 drainage would have to precede deep plowing. Under- 

 drainage prevents the drowning out of crops after heavy 

 rainfalls. It increases the fertility and pulverization of 

 the soil by admitting air. It keeps the ground moister 

 in a dry season. It prevents the washing away of the 

 soil and its fertilizing materials. It permits the farmer 

 to work his land sooner after heavy rain, and earlier in 

 the spring, and it prevents the land from becoming sour 



