ANNUAL REPORT, 1941 17 



manner, except for differences in the use of fertilizers. On two sets of these 

 plots an application of 10-10-10 fertilizer has been made each spring at the rate 

 of 3000 pounds per acre to the plots planted to tobacco, and 2000 pounds per 

 acre to the plots planted to the other crops, in a manner suitable for fertilizing 

 each particular crop. On two other sets of plots no fertilizer has been used, except 

 nitrate of soda which has been applied to all plots alike at the rate of 400 to 500 

 pounds per acre, to aid in reducing the fertility level of the soil in these plots. 

 The crops were all harvested and removed from the plots each year according to 

 regular farming practices. In an additional experiment on a quarter-acre plot 

 considerably removed from the other experiments, tobacco is being grown con- 

 tinuously after tobacco without any fertilizer at all being used. No results can 

 be reported at this time. 



The control phase of the experiment is contingent on the outcome of the other 

 phase; consequently the details of the control phase are not given here. 



Soil Treatments for Tobacco Seedbeds. (C. V. Kightlinger.) Damping-ofif 

 diseases and weeds are troublesome in tobacco seedbeds in the Connecticut 

 Valley. Consequently treatments for their control are important. 



Experimental work to test the effectiveness of spring and fall treatments of 

 seedbed soil by steaming and with formaldehyde, and of fall treatments with 

 chlorpicrin and with calcium cyanamid, was begun in 1940 and continued in 1941. 

 The seedbed used for these tests had been prepared especially for the purpose by 

 inoculating uniformly and heavily with damping-off organisms during the spring 

 of 1940. Evidence that the seedbed was abundantly infested with disease organ- 

 isms was shown by the damping-off of tobacco seedlings grown during the spring 

 and even into late summer of 1940. Care was taken also to make certain that 

 seeds of the more common weeds of tobacco seedbeds were disseminated evenly 

 throughout the soil. 



The steaming was done by the pan method at a steam pressure of about 100 

 pounds applied for 20 minutes, with the pan kept in place for another 20 minutes 

 after steaming had been discontinued. The spring treatment with formaldehyde 

 consisted of a standard solution made of 1 gallon of formalin to 50 gallons of 

 water, applied at the rate of one-half gallon of solution to 1 square foot of soil 

 surface. The fall treatments were steaming, as described above; formaldehyde 

 solution of standard concentration and double the standard concentration, 

 applied in both cases at the rate of one-half gallon of solution to 1 square foot of 

 soil surface; chlorpicrin, applied at the rate of 2 cubic centimeters per square 

 foot of soil surface, and also at double this rate of application, to a depth of about 

 4 inches into the soil, by means of commercial applicator commonly used for the 

 purpose; calcium cyanamid, applied at the rate of one-half pound per square yard 

 of soil surface, and also at double this rate. In both cases, the calcium cyanamid 

 was worked into the soil thoroughly, three-fourths of the total amount to a depth 

 of 4 to 5 inches and cne-fourth to a depth of about 1 inch. The soil treated with 

 calcium cyanamid and chlorpicrin was of proper moisture content for effective 

 treatment at the time and was moistened daily for several days thereafter. The 

 soil temperature at the time formaldehyde, calcium cyanamid, and chlorpicrin 

 were applied in the fall was 67° F., and changed little for a considerable time fol- 

 lowing the treatments. 



No damping-off of tobacco seedlings occurred during the season of 1941, 

 even in the untreated plots of the seedbed, in spite of the fact that tobacco was 

 seeded at double the usual rate and the bed was watered thoroughly every day, 

 and sometimes oftener, to promote damping-off. The unusually warm, dry weather 

 which occurred during the spring of 1941 was sufficient, apparently, to prevent 

 damping-off in spite of the effort that was made to promote its development. 



