256 SOILS AND FERTILIZERS 



of the water. The water should be encouraged to per- 

 colate through the soil rather than to flow over the 

 surface. (See Section 25). 



342. Bacterial Diseases of Soils. Many of the 

 bacterial diseases to which crops are subject are caused 

 primarily by a diseased condition of the soil. These 

 diseases can often be held in check by the right kind 

 of cultivation, by securing good drainage and by proper 

 soil ventilation supplemented with the application of 

 alkaline matter as wood ashes and land plaster. Both 

 bacterial and fungus diseases of soils are capable of 

 being controlled by cultivation particularly when the 

 cultivation improves the general sanitary condition of 

 the soil. With the improvement of the sanitary con- 

 dition, there is less liability of bacterial diseases becom- 

 ing established and causing destruction of the crop. 

 The use of soil disinfectants is possible only when a 

 small area is involved ; they are not applicable to 

 large tracts as they destroy the beneficial as well as 

 the injurious soil organisms. A good sanitary condi- 

 tion of the soil is as essential for the production of 

 crops as are suitable hygienic surroundings for the 

 rearing of live stock. Sunlight and air are important 

 factors in bringing about an improved sanitary condi- 

 tion of diseased soils. By the rotation of crops many 

 bacterial diseases as flax wilt and clover sickness are 

 held in check. Some bacterial diseases are dissemin- 

 ated by the use of infected seed. By sprinkling the 

 seed grain with a disinfectant as a dilute solution of 

 formalin (i pound of formalin in 50 gallons of water) 



