1902.] PUBLIC DOCUMENT — No. 88. 75 



individuals, represent ing in some eases some acres, are now 

 sterilized, and the method has been employed out of doors 

 to some extent. ]Many of the houses treated are 300 or 

 more feet in lenojth and from 40 to 50 feet wide. Some 

 market gardeners have practised sterilization of their houses 

 for three years ; not, however, for the sole purpose of rid- 

 ding the soil of certain disease-producing organisms, as that 

 could be accomplished by one treatment when properly 

 done, but largely for the purpose of increasing their crops. 

 xV great many experiments have been made by this division 

 during the last six years on various crops, in which the 

 growth of plants in sterilized soil was compared with the 

 grow^th of the same species of plants in precisely similar 

 earth not sterilized. The effect of sterilization is quite 

 marked in such experiments. W. W. Rawson, one of 

 our largest lettuce srowers in the State, who has observed 

 the effect of sterilization on his own crops for two or three 

 years, declared that he would rather have one inch of ster- 

 ilized soil on his beds than any fertilizer w^hieh he had ever 

 tried. For the purpose of determining, on a larger scale 

 than we had heretofore shown, the effect heating the soil 

 had upon the acceleration of a crop of lettuce, we made the 

 following experiment in one of our houses : — 



Two beds of nearly equal size were chosen, one of which 

 was treated with hot water until the soil was soaked, and 

 which showed an average temperature of 145° F. at the 

 depth of 4 inches below the surface. The seed and prickers 

 were also planted in boxes of earth which had been heated 

 to 212° F. with steam. The other bed remained untreated, 

 and likewise the soil in which the seed and prickers were 

 started. Other than the hot water treatment given to the 

 previously described bed, no perceptible difference existed. 

 The number of plants in the treated bed was 308 ; the num- 

 ber in the untreated bed Avas 2(U. The results, however, 

 were very marked, as shown below : — 



