49 



a single day, but as we have previously stated we question whether 

 for nematodes there is ever any necessity for treating out of door 

 earth, provided careless inoculation of the soil is guarded against. 

 This method of heating would, of course, produce different condi- 

 tions in the soil from that of steaming. We have never found the 

 dry heating method as satisfactory as the steam method, inasmuch 

 as the former leaves the soil dry and disturbs the mechanical condi- 

 tions, while the latter method leaves it moist and porous and more 

 suitable for plant growth. The iirst notice of the application of 

 steam for sterilizing upon a large scale which we have observed is 

 that used by Mr. W. N. Rudd' of Mt. Greenwood, 111. The steam 

 method has probably been used by other growers even before this 

 but we have taken no particular pains to look up this point. Mr. 

 Rudd employed a box 20 ft. long, 6 ft. wide, and 4.I ft. deep, over 

 the top of which he placed some hot bed sash and in the bottom of 

 the box he ran three lengths of i^ in. steam pipes which were bored 

 every 18 in. with -^\ in. holes, thus allowing the steam when forced 

 in to penetrate through the soil. He does not state the pressure of 

 steam used or the temperature to which the soil reached, but says 

 that when a potato which he usually put in the soil is cooked the 

 earth is ready to be used and that two hours steaming is sufficient 

 for this purpose. 



Mr. Lodder^ later describes a method similar to that used by Mr. 

 Rudd but with some variation in the details of constructing the box 

 and utilizing the steam. He used a box 20 ft. long, 6 ft. wide, and 

 5 ft. deep, which sat upon the ground and was provided w'ith a solid 

 bottom and a cover for the top. The floor of this box upon which 

 the soil was placed was raised i ft. from the bottom, thus forming a 

 superstructure, and consisted of i^ in. steam pipes laid close together 

 which were open at each end presumably for the free circulation of 

 the steam. The main steam pipe passed lengthwise through the box 

 just under the superimposed pipe floor and was li in. in diameter 

 with i in. openings' every foot. The pipes constituting the floor 

 were covered with a layer of straw to prevent the earth which cov- 

 ered them from sifting through. The steam which is let into the 

 pipes soon completely fills the space below the soil and when under 

 pressure passes upwards between the pipes and through the straw, 



1. American Florist, Vol. IX., p. 171, 1896. 



2. Ohio Agr. Expt. Station, Bulletin No. 72- P- 231, 1896. 



