SOIL TREATMENTS AND SEED GERMINATION 



21 



As used by Christoff (18), a dilution of 1:50 (about 1 quart per square foot) 

 injured the germination of seeds of Pinus sylvestris L., but that may have been 

 because he applied it to the soil after seeding rather than before. 



Species vary in their tolerance of this as of other chemicals, and sweet pea 

 was uninjured by applications which were toxic to beet and cucumber. Sweet 

 pea was also the species most benefited by alcohol applied to the soil some days 

 before seeding, while the growth of Arabis was not affected. Although damping-off 

 was not altogether satisfactorily controlled by ethyl alcohol, its severity was 

 lessened by 40 to 60 cc. of 95 percent alcohol, applied to soil 8 days before seeding, 

 and the results, especially with sweet pea, were of sufficient interest to warrant 

 its further consideration as a soil fungicide. 



Salicylic Acid 



This acid and acetic acid were found by Bitting (11) to be more actively fungi- 

 cidal than are some other acids, and Dunn (32) concluded from his work that 

 salicylic acid may be even more toxic, at least to a species of Sclerotinia, than is 

 acetic acid. Further evidence is to be had from the results of Hermann and 

 Neiger (47) and of Janke and Beran (53), who found that very low concentra- 

 tions of salicylic acid are toxic to Tilletia tritici (Bjerk.) Wint. and to Trichothe- 

 cium respectively. Little if any practical use seems to have been made of it as a 

 soil disinfectant, however; although, as a crystalline powder, it has the advantage 

 of being readily applied to soil without the necessity of first preparing either a 

 solution or a dust. 



Post-emergence damping-off, in soils heavily inoculated with Pythium and 

 Rhizoctonia, was not usually well controlled by less than 6 gm., with better 

 although not always complete control by 8 or 10 gm.; but germination and final 

 stands were usually much improved by 4 to 10 gm. This fact, in the case of several 

 species, is brought out in Table 9. 



Table 9. — Effect of S.^i.icylic Acid on Final Stands 



Soil pH values, 2 weeks after seeding, showed no effect from 8 gm. or less — a 

 point to be considered in connection with effects on growth; and it may be noted 

 further that Dunn was inclined to attribute the toxicity of salicylic acid more to 

 the undissociated molecule than to the H-ion. 



As applied to soil, immediately before seeding, salicylic acid, up to 10 gm. 

 did not injure the germination of seeds of any species used. Its effects on their 

 growth were as follows: 



