SOII, MANAGEMENT OR CONTROL 7 



development far from satisfactory, and scientific methods of soil 

 control yet wanting. 1 Recent activities in soil investigations, 

 however, justify the hope that much improvement is to be 

 anticipated, and the application of the modern methods of 

 physical, chemical, and biological research to the soil problem 

 promises a sure and probably rapid advance in this branch of 

 applied science. 



1 It should, of course, be borne in mind that soil factors are not the 

 only ones in crop production. Control by seed selection, breeding of 

 standard types of plants, etc., may be, and probably is, more highly devel- 

 oped than control by soil factors. The same might possibly be claimed 

 for moisture supply in irrigated areas ; but on the other hand, such factors 

 as the bacterial and lower life processes in the soil are generally under 

 little or no control, and as a rule the amount and distribution of sunlight 

 under none at all. A notable effort has been made in the last case with 

 shade-grown tobacco (see Bulletins Nos. 20 and 39, Bureau of Soils, 

 U. S. Dept. Agriculture) and a few cases are known where shade-crops 

 are employed, but not in general agriculture. 



