Treatment of Sick Soils 37 



reduced to three-fourths inch, then to one-half inch, 

 then to three-eighths inch. The pegs are six inches 

 long, and are placed eight inches apart, and consist 

 of one-fourth inch pipe pounded together at the 

 lower end. The steam escapes through a three- 

 sixteenths inch hole at the lower wedge-like end of 

 the pipe. The advantage of this apparatus is that 

 it can be made to fit any bed. At 90 to 100 pounds 

 pressure, more steam will naturally pass through 

 the pipes than at thirty to forty pounds pressure. 

 During the operation, a canvas cover laid on the 

 beds will prevent the rapid escape of steam. 



The Tile Method. This system is at its best when 

 the steam pressure is low, at 25 to 30 pounds. With 

 higher pressures the steam will blow out between 

 the tiles. With this method, therefore, the soil 

 should be sterilized for a longer period of time, 

 from two to four hours, depending on the depth of 

 tile and on soil conditions. Usually the tiles are 

 not laid over one foot deep and from two to three 

 feet apart. The joints of the pipes should be well 

 matched. 



Hot Water Sterilization, Numerous greenhouse 

 men seem to prefer the use of hot water as a soil 

 sterilizer to any other method here mentioned. Mr. 

 Wm. L. Doran of the Massachusetts Experiment 

 Station, who has made considerable study of this 

 method, writes as follows : 



''The soil should be thoroughly dry in the begin- 

 ning so that it will take up the maximum amount 

 of water. Before treatment, it is spaded over to 



