THE PRINCIPLES OF TILLAGE 103 



eept directly from the clouds in the form of precipita- 

 tion. And in very recent times we have even ventured 

 to grow crops in areas where the rainfall is so light that 

 crop failures sometimes occur. In such areas the stor- 

 age and conservation of moisture in the soil is essential 

 to crop production, and tillage is the chief means at 

 man's disposal for accomplishing it. This constitutes 

 the second function of tillage. 



In our cropping and soil management practices we 

 sometimes create in the soil an artificial condition un- 

 suitable to the growth of plant roots. If these practices 

 result in the loss of organic matter, the soil becomes hard 

 and "bakes" easily or blows with the wind. Under such 

 conditions tillage has a third function, viz., to improve 

 the tilth or physical condition of the land as by the 

 pulverizing action of the plow, or the firming action of 

 the packer or the loosening effect of the cultivator. 



In growing crops all portions of the plants are not 

 always removed from the land. The stubble at least, 

 generally remains and must be disposed of. Where 

 strawy manure is applied in an endeavor to maintain 

 the organic matter of the soil or for other purposes it 

 too must be gotten out of the way of seeding machinery. 

 The fourth function of tillage is the disposal of this 

 stubble and manure by plowing it under where it will 

 decay. 



The last important function of tillage is to prepare 

 a satisfactory seed bed or place for the seed to germin- 

 ate'. It is necessary to leave the surface soil in such con- 

 dition that when seed is placed in the ground by the 

 seeding implements used, it will find in sufficient 

 quantities the factors necessary for germination, viz., 

 moisture, heat and air. 



