BULLETIN 453, U. S, DEPABTMEXT OF AGRICULTURE. 



plats and 547 feet in the untreated plats. In the ease of the larger 

 plats, counts of seedlings were made only on sample areas scattered 

 through the plats. The percentages of germination and of death 

 are based on counts of all seedlings on 246 square feet in the treated 

 plats and 145 square feet in the untreated plats. The surviving 

 seedlings were counted on these sample areas and also on additional 

 areas, totaling 406 square feet for the acid plats and 196 square feet 

 for the untreated plats. Damping-ofT is so variable that only 

 repeated and extensive tests of this sort are entirely reliable. 



Table I. — Control of damping-offof pines by three-sixteenths fluid ounce of sulphuric acid 

 per square foot of seed bed applied at sovjing time, Halsey, Xebr. 





Number 

 of sepa- 

 rate tests. 





Absolute results. Relative results. 



Species. 



Treat- 

 ment. 



Germina- 

 tion. 1 



Death 

 per hun- 

 dred seed- 

 lings. 2 



Pinal 



stan 1 



based on 



seed sown. 



Germina- 

 tion. . 



Death. 



Final 



stand. 



Pinus banksiana 3 



11 

 3 

 3 



17 



Acid.... 



None 



Acid.... 



Per cent. 

 32.7 

 20.3 

 6fi.3 



15.2 

 43.7 

 12.0 

 36.7 

 38.7 

 73.7 



Per cent. 

 26.4 

 9.9 

 58.7 

 33.0 

 40.7 

 16.0 



161 

 100 

 132 

 100 

 112 

 100 



35 

 100 



33 

 100 



53 

 100 



267 

 100 

 178 





>.one...J 50.3 

 Acid 1 70. f) 



100 

 254 





None 



Acid 



None 



62.7 



100 



Average 3 



56.3 



44.4 



22.0 

 51.4 



41.9 



16.3 



135 

 100 



43 

 100 



233 

 100 



1 The germination percentage takes into account only seedlings which appear above the soil. Seeds 

 which started to germinate but did not reach the point of breaking through the soil are not included. 



2 The death percentage includes all seedlings which died from damping-<iif and also any which may have 

 died from drought or chemical injury after the seedlings came up^ Seedlings broken by hail or other 

 mechanical means or killed by insects are not included. 



3 Germination and death figures obtained from only 9 of the 11 jack-pine tests. 



The acid in practically all cases caused a marked increase in the 

 number of seedlings that came up, as well as a decrease in the death 

 rate after corning up. Damping-ofT was not entirely controlled. 

 There was still a loss of 22 per cent after germination in the treated 

 plats, but the loss in the untreated plats was nearly two and one-half 

 times as great. The combined effect of increased germination and 

 decreased death rate was a large increase in the number of healthy 

 seedlings produced. (See Table I, columns headed ''Final stand.") 



It is especially to be noted that in jack pine and Norway pine, 

 the species with which the most extensive tests were made, more 

 than 250 healthy seedlings were obtained in the treated plats for 

 every 100 obtained from equal quantities of seed in the untreated 

 plats. The results of the acid treatment of Norway pine are strik- 

 ingly shown by the difference in stand in the treated and untreated 

 plats shown in Plate I, figure 1. 



Since the foregoing tests were conducted, the acid treatment has 

 been put into regular use on all spring-sown beds at this nursery and 

 the success of the treatment further confirmed by the continued 

 good results secured. 



