24 SOILS AND FERTILIZERS 



water. Heavy clays require more cultivation and pro- 

 duce corn which matures later than that grown on soil 

 not so close in texture. Many corn soils contain less 

 sand and clay, but more silt than the figures given.. 

 If a soil has a high per cent of neutral organic matter, 

 good corn crops may be produced where there is less 

 than 12 per cent of clay. Soils with a high per cent 

 of sand are usually too deficient in available water to 

 produce a good crop of corn. On the other hand, 

 heavy clay soils are slow in warming up and thus are 

 not suited to corn culture. The western prairie soils, 

 which produce most of the corn raised in the United 

 States, are composed largely of silt. 



The best types of corn soils have the necessary 

 mechanical composition for the production of good crops 

 of sorghum, cotton, flax, and sugar beets. However, 

 the amount of available plant food required for each of 

 these crops is not the same. 



15. Medium Grass and Grain Soils. For the produc- 

 tion of grass and grain a larger amount of water is 

 required than for corn. The yield is determined largely 

 by the amount of water which the soil contains. For 

 an average rainfall of 30 inches, a good grass and grain 

 soil should contain about 1 5 per cent of clay and 60 per 

 cent of silt. Such a soil ordinarily holds from 18 to 25 

 per cent of water. Many grass and grain soils have less 

 silt and more clay. A soil composed of about 30 per 

 cent each of fine sand, silt, and clay, is also suitable 



