STEAM STERILIZATION OF SKKD BEDS. 7 



added advantage is found in the seasonal distribution of labor, mak- 

 ing it desirable to do the work at this time, when there is no par- 

 ticular rush to complete the steaming. 



Fall steaming has the disadvantage that infected material and 

 weed seeds may be blown into the beds during the winter, but where 

 windbreaks of high, tight board fences are placed around the beds 

 this disadvantage is reduced to the minimum. There also is the 

 added disadvantage in certain cases, particularly where the seed beds 

 are located on low ground, of the ground becoming flooded during 

 winter or spring thaws. The surface water may carry spores from 

 adjoining infected land to the sterilized seed bed. It is necessary at 

 all times to have thorough drainage in and around the seed beds. 



Especially in regions of clay soils w y here glass frames have not 

 come into general use fall steaming finds particular favor because of 

 the practical impossibility of drying the seed-bed soil early enough 

 in a wet spring. 



Where the work is done in the fall all preparations are made as 

 for spring steaming. If manure is used, the quantity added in the 

 fall should be a little more than that ordinarily used in the spring, 

 because of the possible loss by leaching. Commercial fertilizers can 

 be applied safely in the spring. 



EQUIPMENT NEEDED FOR STEAMING SEED BEDS. 



The equipment recommended for steam sterilizing seed beds under 

 average conditions consists of the following: 



A portable boiler of ijO-horsepowor or larger capacity. 



Heavy f-inch steam hose, 25 feet. 



Iron f-inch pipe sufficient in length to carry the steam from the boiler to 

 all parts of the beds. 



Heavy canvas or burlap, 216 square feet. 



A steaming pan to cover an area of about 72 square feet. 



Attachments for the steaming pan, consisting of 4 ring bolts 6 inches 

 long, with 3-inch rings; 4 bars or ax handles; felt packing 2 inches 

 wide, sufficient in length to extend around the pan ; the same length 

 of 4-inch hoop iron or of 2-inch angle iron; one 5-inch nipple 6 or 7 

 inches long, threaded on both ends; two f-inch leather gaskets; two 

 5-inch nuts or threaded washers. 



The boiler is the item of greatest expense, the rest of the equip- 

 ment being comparatively inexpensive. With proper care the entire 

 apparatus should last for a number of years. 



A boiler of sufficient capacity is the essential factor in successful 

 sterilization, because large volumes of high-pressure steam are re- 

 quired. Experience has shown that a boiler of at least 20-horsepower 

 is necessary for efficient steam production when using a steaming 

 pan of the size mentioned above. In some localities, where seed beds 

 have been sterilized with steam for a number of years, farmers are 



