SOIL DISINFECTION WITH HOT WATER. 9 



The object of using fresh greenhouse soil was to determine, if pos- 

 sible, how much of the increased growth in plants in treated soil was 

 due to the absence of the pathogcnes and how much to the chemical 

 or physical effects of the boiling water applied. 



For the bench .experiment, soil from the previous bench experi- 

 ment was used, with which was mixed a quantity of soil from the 

 eelworm-infested tomato bench. 



TREATMENT OP THE SOIL. 



Four-inch pots. — Twelve 4-inch pots were filled with infested soil 

 and treated as follows: Three check pots were immersed in cold 

 water and three each immersed in boiling water at 98° C. for 2h, 5, 

 and 10 minutes, respectively. They were allowed to dry for four 

 days and were then sown to Stone tomatoes. 



This experiment was duplicated, using greenhouse soil presumably 

 uninfested and three additional check pots. 



Eight-inch pots. — Twelve 8-inch pots were filled with infested soil 

 and treated as follows: Three were thoroughly soaked with cold 

 water and used as checks and three each were treated by the applica- 

 tion of 2,000, 3,000, and 4,000 c. c. of boiling water, respectively. 

 All were allowed to dry for four days, and were then sown to Stone 

 tomatoes and Big Boston lettuce, one-half of each pot to each crop. 



The experiment was duplicated with greenhouse soil supposedly 

 uninfested, six checks being used instead of three. 



Certain of these pots were used to determine the temperatiu-es 

 observed in the soil, the time required to raise the soil to the different 

 temperatures, and the length of time the heat was maintained, the 

 results of which are given in Table VI. 



Greenhouse bench. — The bench experiment was an exact repetition 

 of that of Experiment Series I, except as to the cpantities of boiling 

 water applied, which in this case were 11,250, 22,500, and 33,750 c. c, 

 respectively, for sections 1, 2, and 3. These quantities were com- 

 puted as approximately equivalent to 1,000, 2,000, and 3,000 c. c. 

 per 8-inch pot of soil. 



In section 3 a record of soil temperatures obtained during the 

 treatment was kept, as in the case of the 8-inch pots. Two ther- 

 mometers were inserted in the soil in different parts of the bench sec- 

 tion to a depth of 3 to 4 inches and the temperatures recorded. 



RESULTS. 



The details of the results secured from this series of experiments 

 are given in Tables III to VI in the form of germination counts, 

 notes on disease occurrence and on the vigor and size of plants, and 

 temperature records. The experiment was terminated on June 12, 

 and notes on root infections were made as in Experiment Series I. 



