INFLUENCE OF CULTIVATION 35 



at the expense of the subsoil water. 12 Unless rolled 

 land receives surface cultivation excessive losses by 

 evaporation, due to improved capillarity, may result. 

 The use of the roller on clav land during; a wet season 

 results unfavorably. In many localities rolling and 

 subsequent surface cultivation are not admissible on 

 account of the drifting of the soil, caused by heavy 

 winds. 



29. Subsoiling. — By subsoiling is meant pulveri- 

 zing the soil immediately under the furrow slice. 

 This is accomplished with the subsoil plow, which 

 simply loosens the soil without bringing the subsoil to 

 the surface. The object of subsoiling is to enable the 

 land to retain, near the surface, more of the rainfall. 

 Heavy clay lands are sometimes improved by occasional 

 subsoiling, but its continued practice is not desirable. 

 For orcharding and fruit-growing, it is frequently re- 

 sorted to, but is not beneficial on soils containing 

 large amounts of sand and silt. Rolling and subsoil- 

 ing are directly opposite in effect. Soils which are 

 improved by rolling are not improved by subsoiling. 

 The additional expense involved should be considered 

 when subsoiling is to be resorted to. Experiments 

 have not as yet been sufficiently decisive to indicate 

 the conditions most favorable for this practice. 



30. Fall Plowing conserves the soil water, by check- 

 ing evaporation and leaving the land in better condi- 

 tion to retain moisture. Fall plowing should be fol- 



