& FARMERS' BULLETIN 996. 



supplied with their own boilers; in other places one boiler is used 

 cooperatively by several planters. Road rollers, steam tractors, and 

 packing-house boilers are frequently called into use for seed-bed 

 work. In some sections the owners of steam tractors or portable 

 boilers go from place to place, sterilizing beds at fixed prices. Such 

 operators are usually supplied with all necessary equipment, though 

 sometimes they provide only the boiler and a fireman. 



CONSTRUCTION OF THE STEAMING PAN. 



In the permanent seed bed the pan is of such width as to fit snugly 

 within the sides of the frame, and its length varies according to 

 requirements. A pan having an area of 72 square feet is sufficient 

 for a 20 or 25 horsepower boiler, and a larger pan is difficult to move. 

 On a bed 6 feet wide the pan should be 12 feet long. Where only a 



PI6I IT 



PIG. 1. Inverted wooden pan for the steam sterilization of seed beds, showing the con- 

 nection of the steam hose. Note the fine preparation of the seed-bed soil. A light 

 raking only will be necessary before sowing the seed, as all fertilizers are applied 

 before steaming. 



small boiler is, available, the area of the pan should be correspond- 

 ingly reduced, so that the boiler can maintain the desired pressure 

 of at least 80 pounds. 



Sterilizing pans made of galvanized iron have been extensively 

 employed, but as wooden pans are cheaper and are easily made at 

 home, wood is the material now coming into general use. The wooden 

 pan further possesses the distinct advantage of reducing the loss of 

 heat by radiation. 



The pan is siniply a shallow box, 4 inches being the preferred 

 depth. If it is deeper, much of the desired effect is lost through the 

 more rapid cooling of the steam in the larger space exposed above 

 the soil. The frame is made of 2 by 4 inch material ; across this are 

 laid matched boards (J by 4 inches). It is advisable to put white 

 lead in the grooves to prevent the escape of steam. The boards must 

 be securely nailed in the tongue and at the sides to prevent drawing, 

 as they swell by absorption of moisture during the process of steam- 

 ing. These cover boards are further secured by two boards or planks 



