PRESIDENTIAL ADDRESS. 79 



other rich mixtures of manure and organic matter. Under 

 the conditions of growth, moisture and comparatively high 

 temperature, the soils soon become unfitted to grow the 

 desired plants, and in this condition are termed "sick." A 

 cucumber soil is generally good for a year, when it is 

 rejected, and a fresh virgin loam is used. A tomato soil is 

 generally useless after five years. There is always enough 

 manurial matter in the spent soils, in some cases they are 

 even richer than stable manure, but they are so full of 

 •disease germs, eel-worms, plant-lice and fungi, that the 

 plants cannot compete and a poor growth is obtained. 



Various methods of disinfection have been tried in the 

 commercial nurseries, the most successful being high pres- 

 sure steam, low pressure steam and baking. The use of 

 disinfectants is still in the experimental stage, but con- 

 siderable promise has been obtained with formaldehyde at 

 live pence per pound, and carbolic acid at three half-pence 

 per pound. The general application is from a half to one 

 pound per square yard, which is equivalent to two to four 

 pounds per ton. The practical objections to most liquid 

 disinfectants are the price, and the fact that they do not 

 reach all parts of the soil, but are retained near the surface. 

 Baking or steaming works out at from sixpence to one 

 shilling per ton, but much depends upon the resources 

 available. 



Tomato soils which are steamed when not absolutely 

 "sick," cause a better growth at first, but the advantage 

 gained disappears when the plants are fed with manure, as 

 the fruit begins to swell. The backward plants in the 

 untreated soil come forward and overtake those in the 

 steamed soil. It is probably unnecessary to use much 

 nitrogenous manure in steamed soils, as the treatment 

 produces the equivalent of a nitrogenous manuring. The 

 differences, however, are shown in the roots and in the fruit. 



