8 MANUAL OF TREE DISEASES 



the grower must experiment under his own conditions before 

 applying this method generally, else the chemical injury by 

 the acid to the seedlings may be greater than the losses due to 

 damping-off if no treatment were used. If this method can 

 be handled without damaging the seedlings, two special ad- 

 vantages are gained over the other two methods given above. 

 In the first place, dicotyledonous weeds rarely grow in the acid 

 soil and the saving of the expense of weeding will often pay for 

 the treatment. Secondly, the disinfectant is present in the soil 

 throughout the critical damping-off period. This assures 

 complete control sincfe contamination of the beds from neigh- 

 boring soil is not possible and, moreover, conditions of tempera- 

 ture and moisture favorable to seedling growth can be provided 

 without danger. 



The average amount of sulfuric acid is three-sixteenths of a 

 fluid ounce of clear commercial sulfuric acid to each square 

 foot of soil to be treated. A solution is made by adding three- 

 sixteenths of an ounce of the sulfuric acid to each quart of water 

 (this is at the rate of one part of acid to 170 parts of water). 

 This solution should then be applied when the seed is sown 

 at the rate of one quart to each square foot of soil. If the soil 

 is light and sandy and conditions are favorable for excessive 

 evaporation, light watering once or twice a day may be neces- 

 sary to prevent acid-injury. In heavier soils no watering 

 may be necessary. The strength recommended above is suffi- 

 cient to disinfect a soil which is not strongly alkaline. If the 

 soil is naturally acid, the three-sixteenths of an ounce to each 

 square foot may be too much. It would, therefore, -be advisable 

 to divide a given bed into three parts, applying sulfuric acid to 

 each part respectively in the following quantities, one-eighth, 

 one-fourth and three-sixteenths of an ounce in a quart of water 

 to each square foot. From this experiment it may be deter- 

 mined which strength can be safely employed under the exist- 

 ing soil conditions. 



