SOIL MANAGEMENT 



ferent plants. By comparing the amount required to produce 

 a crop with the total annual water supx)ly and taking into con- 

 sideration the capacity of the soil to retain Avater for the use 

 of the plant, approjDriate stejis may he taken to conserve the 

 supply by proper methods of management and thus secure 

 larger crop yields. AVliile the quantity of water varies not only 

 with the kind of plants but also with the climate and season, the 

 following table gives the approximate amount of water neces- 

 sary to produce a joound of dry matter and the number of inches 

 of rainfall necessary to supply the needs for the yields indicated. 



Amount of Water Required to Produce Crops 



Not only the total amount of rainfall, but its distribution 

 throughout the growing season must be taken into considera- 

 tion. Throughout a greater part of eastern United States the 

 rainfall is sufficient for profitable crop yields if proper steps 

 are taken to conserve the moisture. In the dry regions of tlie 

 west special dry-farming methods must be followed to conserve 

 the scant rainfall and insure its storage in the soil until it is 

 used by the crop. In other sections of the west irrigation is 

 practiced to supplement the rainfall. In the east the limiting 

 factor, so far as water supi)ly is concerned, is the capacity of 

 the soil, either naturally or under the good management of the 

 farmer, to retain sufficient moisture within reach of the plant 

 roots to carry them over periods between rains. 



When rain falls upon the surface of a field a part of the water 

 soaks into the soil and another part runs off the surface. If 

 the surface is dry and hard a very large proportion of the water 

 runs off and only a small quantity enters the soil. The part 

 that runs off the surface is not only lost to the plants, but it also 

 carries away with it a large amount of plant food material and 

 may even produce serious erosion of the surface soil. Observe 



