50 MASS. EXPERIMENT STATION BULLETIN 427 



soil and the average of the production on treated soil. In the year 1941-42 the 

 contrast was significant only among Boston Ward and Virginia varieties, which 

 are very susceptible to all of the wilt diseases. For Virginia the difference was 

 3.3 flowers per square foot in favor of the treated soil; for Boston Ward, 4.5 

 flowers. These increases represented a gain of $0.13 and $0.18 per square foot, 

 estimating the value of the flowers at $0.04 each. The other varieties showed 

 smaller contrasts in yield in a range of 1.1 and 1.8 flowers per square foot, or a 

 gross gain of $0,044 to $0,072. With a single exception similar gains are shown 

 between new untreated soil and new treated soil. After deducting $0.01, repre- 

 senting the cost per square foot for material and labor, the gain appears to be 

 worth the effort. 



The old producing plants were removed in June, 1942. Two inches of soil in 

 the benches were removed and two inches of cow manure added. Also 4 pounds 

 of bone meal and 2 pounds of 4-12-4 fertilizer were added to each 100 square 

 feet of bench space. Chlorpicrin was again applied at the rate of 2 cc. per square 

 foot. 



The contrasts in the yield of cut flowers in the production year of 1942-43 

 (Table 16) are not significant. The official report of the New England Carnation 

 Growers Association shows that production during 1942-43 was 18 percent below 

 that of the year 1941-42. This drop, and the fact that no flowers were cut in 

 June, accounted for the drop in production from the previous year. 



The treatment of the old soil with chlorpicrin increased the yield of flowers 

 only slightly, '^he difference between the number of flowers from untreated new 

 soil and the average from the treated soil ranged from 0.2 to 1.1 flowers per 

 square foot, representing a gross gain of $0,008 to $0.04. A gain of 1.3 flowers 

 or $0.05 is shown by Olivette, based on the yields on untreated soil the second 

 year of use and on treated soil. After a deduction of $0.01 for costs, the invest- 

 ment appeared to be of doubtful value. 



Bickerton (5) reported a net profit of $0.23 to $0.38 per square foot from the 

 treatment of the bench soil with chlorpicrin, and on this basis it was asserted 

 that the treatment would appear to solve the problem of low and decreasing 

 yields of flowers on the same soil used again. 



Some growers from custom have preferred steaming, and this, in the judgment 

 of New England carnation growers, is the most popular method. Disinfestation 

 of soil for growing the young stock plants is generally practiced and various ways 

 of steaming the soil are also practiced. Resoiling the benches at the end of the 

 growing season is one of the most costly operations in carnation culture. With 

 serious shortages in man power, the continued maintenance of the old soil in a 

 sanitary and highly productive state by any combination of sterilization and 

 fertilization instead of replacement is highly desirable. 



The various reports on the value of soil sterilization in relation to the control 

 of carnation wilt diseases and flower production are not entirely favorable. 

 Examples of bench soil sterilization with steam have been observed in many 

 growers' establishments, but the apparent effect on disease control and growth 

 frequently has been either lacking or inconsistent. Even in instances where 

 disease is prevalent year after year, and where soil sterilization would appear to 

 be desirable, no apparent improvement is shown. In an open discussion on the 

 subject on soil sterilization by experienced and capable New England carnation 

 growers no conclusive evidence of disease control from treating the soil was 

 admitted.* Nevertheless, striking contrasts showing the value of treating old 

 or used soil with steam or chlorpicrin are sometimes apparent (Fig. 13). 



*Reported by K. F. McCuUy, Secretary-Treasurer, New England Carnation Growers .Associa- 

 tion, in Florists' Review 94 (2426) : 19. May 25, 1944. 



