68 THE ESSENTIALS OF AGRICULTURE 



medium for the growth of bacteria and fungi, particularly when 

 it contains considerable quantities of organic matter. The bac- 

 teria and the fungi existing in all soils are necessary to fertility. 

 To be sure, there are forms of bacteria present which under 

 certain conditions may work against the farmer's interests by 

 undoing what helpful bacteria have done, but in soils which are 

 well drained and properly cultivated the action of these injurious 

 forms is unimportant. 



The functions which these organisms perform are mainly in 

 connection with the decay of organic matter. The supplying of 

 plants with nitrogen in a form adapted to their needs is almost 

 entirely due to the activity of these lower organisms. They also 

 perform a valuable service in making available other necessary 

 plant foods, such as phosphorus and potassium. Their effect in 

 bringing about a loose, friable, or crumbly condition of the soil 

 (largely through their action upon organic matter) is of no small 

 importance. 



The beneficial organisms are greatly stimulated in their de- 

 velopment by thorough soil aeration and warmth. Since drainage 

 removes standing water, admits air, and warms the soil, it is one 

 of the most important means of influencing the development of 

 beneficial organisms. A favorable degree of moisture in the 

 soil is necessary for the work of these organisms just as it is 

 for agricultural plants. Tillage, therefore, exerts an important 

 influence upon the work of these organisms because it aerates 

 and warms the soil, conserves moisture, and has a beneficial 

 effect in other ways. The addition of organic matter and of 

 lime likewise stimulates the development and action of the bene- 

 ficial organisms. It is a part of the modern farmer's education 

 to understand the handling of soils so as to favor the develop- 

 ment of these organisms ; also to maintain the proper degree 

 of moisture and the most suitable temperature and texture of 

 the soil for the highest development of the crops he seeks to 

 grow. Soils which are cold may be made warmer, those which 

 are wet may be made dry, and those which are " dead " may 

 be made " alive." 



