826 Sterilisation of Soil for Glasshouse Work. [jan. 



with plant roots or food-making bacteria; (3) fatal to eel- 

 worms and other animals, to fungus spores, and to organisms 

 interfering with the food-making bacteria; (4) no more 

 harmful to food-making bacteria than a temperature of 180 0 F. 

 Some commercial waste product is clearly indicated, and a 

 suitable substance could no doubt be found among the 

 numerous coal-tar products. Our own experiments have been 

 made with pure substances, with the view of settling the 

 various preliminary problems ; it is now possible to study 

 some of the waste products obtainable by the grower. 



Conclusions. 



1 . Partial sterilisation of soil increases the supply of food 

 for the plant, somewhat alters the growth of the plant, and 

 kills insect pests. 



2. It may cause a temporary retardation in germination and 

 in early growth, the amount of which varies according to the 

 nature of the soil, the seed, and the general conditions. 



3. In our experiments it has not proved advantageous for 

 pot work where abundant supplies of clean virgin soil and 

 manure are available. 



4. It is, however, very useful for work with borders, cold 

 frames, and for plants that are to run for some time without 

 manure. It leads to better root development, sturdier and 

 healthier plants, earlier flowering, more prolific fruiting, and 

 better quality of fruit. 



5. It is particularly useful for commercial glasshouses where 

 soil pests are a source of trouble, and soil "sickness " sets in. 



6. At present the most effective method of partial sterilisa- 

 tion is to heat the soil to a temperature above 140 0 F., but not 

 exceeding 212 0 F. Very satisfactory results have been 

 obtained between 180 0 and 200 0 F.; \ cwt. or less fuel is 

 required per ton of soil ; capital and labour charges depend 

 on the speed at which the process is to be worked. Our 

 experiments indicate that effective chemical treatment is also 

 possible, and would, of course, be much simpler, but we have 

 not yet tested a sufficient number of commercial products to 

 discuss the problem from the grower's point of view. 



