July 15, tgio 



Presoak Method of Seed Treatment 



387 



able to control by formalin and copper sulphate. So far, this method 

 has been tested on the germination of oats, barley, and maize with 

 results similar to those obtained for wheat. Copper-sulphate injury can 

 be prevented for Tennessee winter barley as shown above. The results 

 thus far obtained with the presoak method of treatment, using formahn 

 I to 320 on oats and barley and formalin i to 200 on maize, are given 

 in figure 8. Oats and barley were soaked in water 10 minutes, drained, 

 and kept moist 6 hours, then soaked in formalin i to 320 for 10 minutes, 

 and covered 6 hours. Maize, which absorbs water much more slowly 

 than wheat, oats, or barley and is also less susceptible to formalin injury, 

 was given a lo-hour presoak — that is, 10 minutes in water, draining and 

 covering for 10 hours, followed by 4 hours' formalin i to 200 treatment. 



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Fig. 9. — Curve showing rate of absorption of water by dry wheat seeds. 



In another case it was given a lo-hour actual soaking in water, followed 

 by the treatment. 



The presoak method is evidently applicable to these cereals also, as 

 a means of preventing seed injury due to disinfectants (Pi. 81, 82); and 

 the possibility of its application for other kinds of seeds is obvious. 



GENERAL DISCUSSION 



As a result of these experiments several facts stand out clearly. First, 

 in all cases, with each variety of wheat, barley, oats, and maize tested, 

 the presoak method minimized or eliminated the injury to seed germina- 

 tion due to the use of formalin and copper sulphate. Second, as shown 

 in the illustrations, a marked stimulation of growth was usually produced. 

 Third, the presoak method proved fully efficient as a means of destroying 

 or preventing the growth of the bacteria of the blackchaff disease borne 

 on the seed and can undoubtedly be apphed for the prevention of other 

 diseases. Fourth, the method is simple and adapted to field conditions, 

 since any farmer can apply it. 



The cause of the first-mentioned eflfect of the presoak treatment may 

 be partly accounted for upon an analysis of figure 9. This represents 

 the rate of absorption of water by 10 gm. each of dry seeds of two wheat 



