346 



SOIL PHYSICS AND MANAGEMENT 



which we are familiar. The soil in which they grow must be suf- 

 ficiently loose so the roots have little difficulty in penetrating it. 

 The growth they make depends to a large extent on the area over 

 which the roots spread. Hence the necessity of producing a deep, 

 mellow seed bed that will allow free root development. 



Clods are of no value in a field, but are always a source of annoy- 

 ance. They are generally the products of shiftless and unscientific 

 methods of farming rather than of some inherent fault or bad 

 quality of the soil. Soils if worked at the proper time and after 

 proper preparation respond to good tillage. The disk is one of the 

 best implements for preventing the formation of clods and, to- 

 gether with the culti-packer, for destroying them if they once form. 



Fro. 165. Grain produced from five tenth-acre plots prepared in different ways lor winter 

 wheat. (L. E. Call.) Kansas Station. 



Clods are of no use to a growing crop, but on the contrary lock 

 up large quantities of food and become prisons for millions of bac- 

 teria that would otherwise be working for the farmer. Fields are 

 sometimes seen in which at least one-third of the plant food of tbe 

 plowed soil is locked up in clods. Even if the clods are turned 

 under and covered by mellow, moist soil, weeks are required before 

 they become thoroughly moistened unless rain falls. 



1. Wheat. Plowing for wheat should be done as soon as pos- 

 sible after the removal of the preceding crop and from five to seven 



