18 BULLETIN 453, U. S. DEPARTMENT OP AGRICULTURE. 



In most of the treatments listed in Table III the substance used 

 was applied just after the seed was sown and covered. Formaldehyde 

 kills some of the seed if so used and was accordingly applied several 

 days before seed sowing. Either the soil was treated a week or more 

 before sowing in the formaldehyde plats and kept covered with heavy 

 paper for a few days after treatment, or else the treatment was made 

 but two or three days before sowing and no paper was used. Even 

 with these precautions part of the seed was killed in the tests at 

 Burlington, the Kansas sand hills, and Glenview. Zinc ohlorid killed 

 the dormant jack-pine seed hi two heavily treated plats at Garden 

 City which were sown and treated in the fall and remained dormant 

 throughout the winter. It ordinarily produces no such effect. Sul- 

 phuric acid has also shown a tendency to decrease the germination 

 percentage in two or three tests of fall treatments, but ordinarily has 

 no such effect in spring-sown beds. It has never had more than a 

 slight delaying effect on germination except during very wet, cold 

 weather, and its harmful effect on dormant seed hi spring-sown beds 

 is negligible. Copper sulphate shows even less tendency than sul- 

 phuric acid to injure dormant seed. Sulphuric acid, copper sulphate, 

 and zinc chlorid are all inclined in some soils to injure the root tips 

 of seedlings just after germination begins; on such soils the injury 

 to seedlings can be prevented by very frequent watering during the 

 germinating period. Column 7 of Table III indicates for the best 

 strength of each successful treatment whether or not such extra 

 watering is required. It will be noted that in formaldehyde beds 

 extra watering is nowhere necessary. For the other three disinfec- 

 tants it is more commonly necessary on very light sandy soils than on 

 heavy soils. 



Air-slaked lime, powdered sulphur, and charcoal were applied dry, 

 and hi the tests reported by the writers were raked into the upper 

 3 inches of soil. Copper sulphate was applied hi the form of dry 

 powder in the tests reported by Spaulding. 1 Sulphuric acid, formal- 

 dehyde, zinc chlorid, and hi the tests reported by the writers copper 

 sulphate were applied in solution. The strength of all treatments 

 is expressed in the number of ounces of substance per square foot of 

 bed. For sulphuric acid and formaldehyde the fluid ounoe (29.574 

 c. c.) is the unit of measure, while for all other substances the avoir- 

 dupois ounce (28.35 gm.) was used. Three-fourths of an ounce per 

 square foot is practically equivalent to 1 ton per acre. The amount 

 of water used in dissolving the disinfectants varies from 1 to 2 J pints 

 per square foot. For a soil already wet 1 pint is sufficient; for a dry 

 fine-textured soil 2\ pints may be needed to secure a proper distri- 

 bution of the disinfectant. Ordinarily, 1^ or If pints per square 

 foot are satisfactory. 



1 Spaulding, Perley. The treatment of damping-off in coniferous seedlings. U. S. Dept. Agr., Bur. 

 Plant Indus. Circ. 4, 8 p. 1908. 



