Aprils, 1920.] Agricultural Gazette of N.S.W. 28T 



having been connected to the engine and the frame placed over the seed-bed j, 

 the steam is turned on and allowed to pass into the frame for half an hour. 

 The frame is then lifted to another portion of the seed-bed and placed so that 

 one edge overlaps the portion of the grovind previously treated, and the 

 operation of steaming is repeated. As the frame is shifted to each new patch, 

 the portion from which it has been removed is covered with hessian so that it 

 may retain its heat as long as possible, and the whole operation is repeated. 

 until a sufficient area for the purposes of the grower has been dealt with. 



In our experiments it was found that after about a quarter of an hour the 

 frame began to lift slightly and there was a tendency for some of the steam, 

 to escape at the sides. This was easily overcome by putting two heavy logs 

 on the top of the frame and shovelling earth around the edges so as to bank 

 them up. The heat given out by the steam penetrates very de(iply into the 

 earth, and by use of the hessian the heat is retained for a considerable time. 

 In one experiment, before commencing, three potatoes were placed 3 inches,, 

 4 inches, and 6 inches' below the surface of the ground. When the frame 

 was removed after half an-hour's steaming, the two potatoes nearest the 

 surface were completely cooked, and the deeper one nearly so. It is hardly 

 likely that any fungus spores would survive a temperature capable of 

 producing this result. 



Effect of the Treatment. 



The beds wei*e sown a few days after the steaming operation h,ad been 

 completed ; the subsequent growth of the seedlings was good. The out- 

 standing feature of the treated beds was their absolute freedom from every 

 kind of weed. The veiy tedious operation of weeding tobacco seed-beds — 

 one which must be performed over and over again — is thus entirely elim- 

 inated. On the major portion of the treated beds the plants were strong 

 and healthy ; on one small spot, however, the seedlings failed to grow. The 

 reason for this is not obvious, but we hazard the conjecture that it was due 

 to want of sufficient water, for it has been found that steamed soil requires a 

 larger amount of water than unsteamed. 



It is reasonable to suppose that soil steamed as described is sterile, but plants 

 grown upon it enjoy no immunity if an infectious disease breaks out in their 

 vicinity. As a matter of fact, " blue mould " did break out in some tobacco- 

 seed-beds not far removed from the treated beds, and a few days, afterwards 

 the plants here also became affected. As already pointed out, the spores of 

 " blue mould " are produced in countless millions and are likely, therefore, to 

 be carried from one place to another by the wind or by workmen, on their 

 person or on their implements. 



Conclusions. 



In agriculture it is not permissible to draw definite conclusions from one 

 season's results, but our inferences from this year's experiment are as 

 follows : — 



1. Steam sterilization may easily be practised by tho)se who have the 

 necessary power to maintain steam at a pressure of TO lb. pec- 

 square inch. 



