CHAPTER 2 



SICK SOILS 



When a soil is sick, either because its beneficial 

 bacteria do not perform their functions properly, or 

 because of abnormalities in its chemical or physical 

 properties, careful treatment and proper cultural 

 methods may restore it to health. But when a soil 

 becomes sick and unproductive because parasitic 

 forms gain a foothold in it, much greater skill and 

 knowledge are required to cope with the problem. 

 Its solution is of the greatest economic importance 

 to the gardener and to the greenhouse man. 



Parasitic fungi, upon finding their way into a soil, 

 do not necessarily interfere with the work of the 

 beneficial bacteria, such as the ammonifiers and ni- 

 trifiers, for instance. Nor do they always influence 

 the chemical or physical nature of the soil. Many of 

 them directly attack the crop itself, causing serious 

 diseases in the plants. 



Damping Off 



This disease is 'very familiar to every grower of 

 plants. It is peculiar to seedlings or tender plants, 

 and is very prevalent in the greenhouse, the hot bed, 



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