92 VEGETABLE FORCING 



boiler pressure ranging from 50 to 70 pounds. A highly 

 successful grower has found 20 pounds satisfactory when 

 pans are used over loose soil. 



Preparing soil. Previous to sterilizing with either 

 steam or formalin, the soil should be manured and 

 plowed or spaaed ready for planting. If lime is to be 

 used, it also should be applied before the soil is sterilized. 



It is important for the soil to be rather open in struc- 

 ture, so that the steam will penetrate every particle. It 

 should also be quite moist, but not wet. More formalin 

 is required in dry soil, and the results in dry soil with 

 either method are unsatisfactory. The various organ- 

 isms are in a live state or more active in moist soils, and 

 in this condition they succumb more quickly to the 

 sterilizing agents. 



Devices for sterilizing. Various devices are employed 

 for sterilizing by steam. Among them may be mentioned 

 boxes, pans, perforated iron pipe, perforated pipe pegs 

 and ordinary drain tile. In the selection of a plan there 

 are two main considerations, viz., efficiency and economy. 

 A plan may be very efficient but highly expensive, 

 especially in regard to the amount of labor involved. 

 There is very little specific information on the relative 

 efficiency of the various plans, and it is probably not so 

 much a question of plan as of thoroughness and good 

 management. All of the five devices which will now be 

 described have been used with success. 



Boxes. During the earliest days of steam sterilization, 

 boxes were used exclusively. They varied greatly in size, 

 proportions and construction, but fundamentally they 

 were similar. The general scheme was to make wooden 

 boxes of convenient size, and to place perforated pipe in 

 the bottom of them. The boxes were covered to confine 

 the steam, and the joints were made as tight as possible. 

 The pipe in the bottom of the boxes was usually 1 inch or 

 14 inches in size and connected with headers 2 inch 



