80 R. GREIG-SMITH. 



The roots of the plants in the steamed soil are much more 

 fibrous, and the fruit is generally greater in quantity and 

 better in quality. A mechanical trouble arises in steaming 

 cucumber and chrysanthemum soils, for after the steaming 

 the fibrous nature of the soil is lost, and a judicious mixture 

 with a new soil is advisable. Still the rejuvenated soil is 

 as good as new soil, and generally the cost of steaming is 

 less than tbe cost of new soil. 



In "sick" soils the effect of steaming or baking, or of 

 disinfectants, is very marked as the sickness is cured and 

 the plants grow in a healthy manner and with luxuriant 

 foliage. 



Partial sterilisation has not and probably never will be 

 attempted in the field, as to be effective the cost would be 

 prohibitive. It is true that carbon disulphide has been 

 used to combat the soil-sickness and phylloxera of the 

 vine, but for ordinary crops the treatment would not be 

 economical. Lime has been used, and especially the old 

 fashioned gas-lime, rich in calcium sulphide and polysul- 

 phides, in checking the ravages of finger-and-toe disease of 

 cruciferous root-crops. Lime is used in ordinary farming 

 practice, more to counteract soil acidity and to favour the 

 growth of clover, than to partially sterilise the soil. Possibly 

 if partial sterilisation ever is attempted with our crops, 

 it will be with potatoes, and the agent may possibly be a 

 lime and sulphur compound, for it gives most promise of 

 being purchasable at a low price. 



In Australia, the tropical and subtropical sun is continu- 

 ally subjecting the soil to a process of partial sterilisation, 

 not only by the high daily temperatures, but also by the 

 repeated and extensive drying or desiccation. So much is 

 this the case, that probably the action of the limiting factor 

 is at a minimum for the greater part of the year. During 

 my experimental work, I have found that it is hopeless to 



