53 



to prevent heavy losses under unfavourable circumstances, while 

 the Avithholding of water often does as much direct harm as the 

 affection which it is sought to avoid. 



The use of imperfectly rotted manure, of lime, of wood ashes, 

 and of a mixture of coal and wood ashes are indicated as having 

 had bad effects. 



The one means so far discovered which can be relied upon 

 to give satisfactory results under any reasonable conditions is the 

 disinfection of the soil. The question remains as to which of the 

 various methods available for this purpose it is most convenient 

 to adopt. The use of steam or of formaldehyde has been widely 

 recommended, but these methods are so expensive as to be im- 

 practicable except for relatively small quantities of valuable 

 material, as in green-houses or market gardens. 



For the broader requirements of nurserymen the treatment 

 finally adopted by the authors of the bulletin under review consists 

 in the application in standard soils of three sixteenths of a fluid 

 ounce of connnercial sulphuric acid to each square foot of seed 

 bed, applied in solution in water immediately after the seed is sown 

 and covered. This has i)roved more reliable than the more ex- 

 pensive methods mentioned above. 



The amount of water used to carry the disinfectant does not 

 appear to be a matter of importance, j^rovided that the necessary 

 amount of the acid is applied to each unit of area. The quantity 

 used by the authors varies from 1 pint per square foot when the 

 soil is wet to 2 pints when the soil is dry. There is a possibility, 

 especially in light soils, of a concentration of the acid by evapora- 

 tion to a strengtli injurious to the root-ti]:)S, which in practice has 

 been found to be completely avoidable by watering the beds fre- 

 quently during the period of germination. When the root-tips 

 have penetrated to a depth of half an inch this is no longer 

 necessary. 



Tliere are diiferences in the amount of acid required for suc- 

 cessful results in different soils. In sandy soil which was pro- 

 bably somewhat alkaline, a heavier application, one-fourth to three- 

 eighths of an ounce, was indicated. In a fine sandy soil which was 

 probably already acid, chemical injury to seedlings was more diffi- 

 cult to avoid, and reduction of the acid to one-eighth of an ounce 

 was advisable. On heavier soils the use of five eighths of an ounce 

 produced no injury, and reduced losses by damping-olf to less than 

 1 per cent. 



On a soil with a high carbonate content, evidenced l^y a vigorous 

 ■effervescense when the acid was applied, the method was found to 

 be ineffective. On this soil the use of copper sulphate, one-fourth 

 ounce per square foot, gave good results. This substance was ap- 

 plied in the same way as the acid, and the same precaution to avoid 

 chemical injury was found necessary. 



An interesting indication was given Ijy the experiments of 

 the elfectiveness of cane sugar, 2^ oz. to the square foot, in the 

 control of damping-off. The authors point out that if some un- 



