56 



SOILS AND FERTILIZERS 



bring about decomposition, which operation is performed 

 by bacteria, fungi and molds. It has already been pointed 

 out that unrotted organic matter has very little useful- 



Fig. 10. — The upper figure represents a furrow slice laid too flat for the 

 most rapid decay of organic matter when present in large quantity. The 

 lower illustration shows a better furrow angle. 



ness and may be injurious. The conditions that favor the 

 rapid and desirable rotting of organic matter are the fol- 

 lowing : 



(1) An amount of moisture that will not fill all of the 

 pore spaces, but that will provide water required by 

 the organisms that decompose the organic matter. The 

 soil moisture content most favorable for plant growth is 

 about the same as that most favorable for rotting organic 

 matter. 



(2) The soil should be loose enough to allow air to pene- 

 trate readily, but not so loose as to leave large air spaces. 

 Air is necessary to the activity of those organisms that pro- 

 duce a desirable kind of decomposition. A compact soil, 

 or a very wet soil delays the rotting process and favors the 

 growth of organisms that form products poisonous to agri- 

 cultural plants. 



