14 BULLETIN 169, U. S. DEPARTMENT OE AGRICULTURE. 



The decrease in stand both with decreasing amounts of watering 

 and with increasing amounts of acid was sufficiently consistent in 

 this experiment to establish beyond a reasonable doubt the relation- 

 ship, both of the amount of acid used and of the amount of watering 

 done, to the acid injury. In the weakest acid plat with the inter- 

 mediate watering, no appreciable injury occurred. Because of the 

 variation in germi n ation aside from the influence of acid, the results 

 were not always quite as consistent as in this series, but no reason has 

 been found to doubt the relation between the amount of acid and 

 the extent of injury in beds treated at sowing. 



INJUKY TO PINES BY SULPHURIC ACTD APPLIED BEFORE SOWING. 



In treating beds with sulphuric acid to kill fungous parasites the 

 attempt was made to evade toxic action on the seedlings by applying 

 the acid a number of days before sowing. Jack pine was also used 

 in most of these tests. In such cases the beds were ordinarily hoed 

 and raked just before they were sown, so that the upper 2 or 3 inches 

 of soil was well mixed after the acid was applied. In the plats treated 

 at sowing there was the possibility that the injury was limited to the 

 surface five-eighths of an inch of soil, simply because this layer of 

 soil had acted as a trap for the acid, absorbing most of it at the time 

 of application. In the case of plats treated before sowing there was 

 no such possibility. The seeds were in most cases covered with about 

 one-fourth of an inch of soil taken from the upper 1 to \\ inches of 

 the soil of a near-by area that had been given the same treatment as 

 the plat sown. Considerable injury occurred in plats which received 

 0.25 and 0.375 ounce of acid nine days before sowing (20 days in all 

 elapsing before germination), although the treated plats received 

 approximately 1.6 inches of water five days after sowing, followed by 

 0.3 to 0.4 of an inch daily till after germination. The slight drying 

 of the surface soil which resulted in the injury on these plats took 

 place the first day after germination, 21 days after the application of 

 the acid. 



In another series, using the same species of pine, amounts of 

 0.281, 0.375, and 0.687 ounce of acid per square foot were applied 11 

 days before sowing, two plats receiving the latter amount. Four 

 days after sowing, the plats were given approximately 1.6 inches of 

 water, followed by waterings of approximately 0.3 to 0.4 inch on 

 the sixth, eighth, ninth, tenth, and eleventh days from sowing. 

 Germination took place on the eleventh day, 22 days after the 

 application of the acid, and on the morning of this day the soil 

 surface became somewhat dry, but not dry enough to cause appre- 

 ciable drought injury in the nonacid plats. As shown by later 

 examination of the length of the acid-injured roots, injury took 



