SOIL TREATMENTS AND SEED GERMINATION 



15 



We come now to the use of vinegar applied to the surface of soil after seeding. 

 It cannot then be worked into the soil and is, therefore, more concentrated near 

 the surface of the soil and near the seeds. Vinegar, with or without dilution, was 

 thus applied in several experiments and its effects on germination are summarized 

 in Table 7. 



Quantities of vinegar which were entirely safe if worked into the soil before 

 seeding were injurious to seeds of some of the same species if applied to the 

 surface of the soil immediately after seeding. The important point seems to be 

 not so much when as how vinegar is applied, for there was often no more than 

 10 minutes' difference between applications made after seeding and those made 

 before. 



Vinegar applied after seeding was least injurious in the case of seeds which 

 germinate relatively slowly, such as Opuntia or even pepper; and it was most 

 injurious in the case of seeds which germinate relatively promptly, before enough 

 acetic acid has escaped from the soil, such as cabbage and Calendula. Seeds 

 and seedlings of Opuntia, which are prone to damp-off, were well and safely 

 protected by 237 cc. of vinegar, undiluted, applied to soil after seeding. Such 

 an application may, however, be decidedly unsafe with some other species which 

 germinate more rapidly. 



Germination was injured more than was growth. Growth of the species named 

 in Table 7, with the exception of cabbage, was unaffected or improved by 237 cc. 

 of vinegar diluted with an equal volume of water. Growth of cabbage was injured 

 by as little as 189 cc. thus diluted. 



Not only vinegar, but also acetic acid (80 percent) 8 cc, and formic acid 3.5 cc. 

 per square foot were found to be considerably more injurious when applied to 

 soil after seeding than before, and, as has already been said, as little as 2.3 cc. 

 formaldehyde applied after seeding is injurious to crucifers. 



It is not at all certain that such light applications would be for long effective 

 in preventing fungi from growing up from the soil below, but the method has the 

 advantage of convenience and is now being investigated further. 



