PHYSICAL PROPERTIES OF SOILS 43 



35. Depth of Plowing. The depth to which a soil 

 should be plowed in order to give the best results must, 

 of necessity, vary with the conditions. Deep plowing 

 of sandy land is not advisable, particularly in the spring. 

 On clay land deeper plowing should be the rule. The 

 longer a soil is cultivated, the deeper and more thorough 

 should be the cultivation. While shallow plowing is 

 admissible on new prairie land, deeper cultivation 

 should be practiced when the land has been cropped 

 for a series of years. Also, the depth of plowing should 

 be regulated by the season. In prairie regions, and in 

 the northwestern part of the United States, shallow 

 plowing is more generally practiced than in the eastern 

 states. Deep plowing in the fall gives better results 

 than in the spring. It is not a wise plan to plow to the 

 same depth every year. Professor Roberts says : 16 " If 

 plowing is continued at one depth for several seasons, 

 the pressure of the implement and the trampling of the 

 horses in time solidify the bottom of the furrow, but if 

 the plowing is shallow in the spring and deep in sum- 

 mer and fall, the objectionable hardpan will be largely 

 prevented." 



In regions of scant rainfall deep plowing of silt 

 soils should be done only at intervals of three or 

 five years, but with an average rainfall, deep plowing 

 should be the rule on soils of close texture. The 

 depth of plowing should ^ be varied to meet the re- 

 quirements of the crop and soil and the amount of 

 rainfall. 



