PREPARATION AND CULTIVATION OF THE SOIL 71 



the best seed-bed is one compact enough to permit the 

 capillary moisture to move toward the seed, and yet loose 

 enough to permit air also to come in contact with the seed. 

 Roots, as well as seeds, require enough compactness of soil 

 for the easy movement of capillary water toward the 

 thirsty root-hairs, and likewise sufficient looseness of soil 

 to admit a little air and to allow the roots to grow freely 

 in any direction. 



If the soil is in good condition when plowed, the neces- 

 sary compactness can often be had simply by allowing 

 several weeks 

 for the rains to 

 make it compact 

 or to settle it. 

 Sometimes it is 

 necessary to use 

 implements for FIG. 47- A PLANK DRAG 



this purpose, especially the harrow, the plank drag, or the 

 roller. Clods are most easily broken when first plowed. 

 Let the harrow therefore follow close behind .the plow. 

 After plowing or rolling, the harrow should be used im- 

 mediately so as to leave on the surface a loose layer of 

 dry soil. This loose surface layer contains so many and 

 such large air-spaces that the moisture from the compacted 

 layer below cannot easily cross these and rise to the sur- 

 face, where it' would be evaporated. Air-spaces in the 

 loose surface layer do good by imprisoning the moisture 

 in the lower layers. 



The largest crops are generally made on those soils 

 where the roots of cultivated plants grow deepest. This 



