Soil Disinfection 



463 



perforated teeth, has proved satisfactory under some condi- 

 tions. 



Surface firing. — Surface firing of seed beds has been a 

 common practice for years in some tobacco sections, par- 

 ticularly in Kentucky and other southern states, the end in 

 view being the improvement of the tilth of the soil and the 

 killing of weed seeds rather than the destruction of any 

 fungous disease. In Italy burning is now considered a part 



Fig. 237. — Disinfecting soil with a Sargent disinfector. Original. 



of the regular method of tobacco seed-bed preparation, it 

 having been resorted to as a preventive of root-rot due to 

 Thielavia. 



Two methods of surface firing are in vogue; the first, 

 by direct firing, the second requiring the use of a pan. In 

 the direct method, the land to be disinfected is first thor- 

 oughly pulverized and manure applied. It is then covered 

 with straw, brush, and wood sufficient to make a hot fire. 

 This is ignited and allowed to burn an hour or so, after 

 which the ashes are raked into the surface soil. 



The second method, pan firing, consists in the use of a 

 sheet-iron pan, 3' by 9', which is set in the middle of the seed 



