6 Diseases of Truck Crops 



functions. A recent exhaustive study x of Actinomy- 

 ces, or thread bacteria, in the soil seems to show that 

 they serve to decompose grass roots, being more 

 numerous in sod than in cultivated land. Other 

 groups of bacteria undoubtedly must perform other 

 important functions. 



The mere presence of friendly bacteria in the soil, 

 however, would be insufficient to assure the welfare 

 of our cultivated lands. What concerns us most is 

 the work that they perform. Most of the plant's 

 food as it is found in the soil is in a crude and una- 

 vailable form. The bits of mineral matter, the 

 manure or fertilizer, in the truck patches all con- 

 tain plant foods but in a form which plants cannot 

 readily use; they must be softened and predigested 

 and this work is done by the friendly organisms. 

 Plant food is therefore directly dependent on the 

 work of these minute, scavengers. An intimate re- 

 lation exists between the higher and the lower forms 

 of plant life, the one depending on the other. 



DISTRIBUTION OF SOIL BACTERIA 



For a practical purpose we ought to know in what 

 soil and at what depth the beneficial bacteria are 

 most likely to abound. Since the presence of bac- 

 teria is necessary to maintain the fertility of a normal 

 healthy soil, it is essential to study the main factors 

 that determine their increase or decrease. We can- 

 not expect to find them equally distributed in differ- 



1 Conn, Joel H., New York (Geneva) Agr. Expt. Sta. Bui. 52 : 

 3-1 1, 1916. 



