70 BULLETIN 479, U. S. DEPARTMENT OF AGRICULTURE. 



sown and covered at the rate of three-sixteenths of a fluid ounce in 

 solution with 1 quart of water to the square foot of seed-bed sur- 

 face. This acid applied at the rate designated has been found very 

 efficient. When acid is used seed beds must be kept well moistened 

 during the germination period. Neglect of this results in concen- 

 tration of the acid in the surface soil through capillary rise of the 

 solution, and the growing apex of the radicles of the germinating 

 seed are killed, which may result in the death of the plants. For 

 some other nurseries different amounts of acid were found success- 

 ful; at a good many places it w T as found unnecessary to take 

 any special precautions in the way of extra watering in the acid- 

 treated beds. The results obtained from this treatment are in 

 accord with what has been found true elsewdiere, that damping-off 

 is much less prevalent in soils of an acid than in those of a weakly 

 alkaline reaction. Experiments at the Vermont Agricultural Ex- 

 periment Station x indicate that damping-off is likely to be less 

 serious in beds to which there has been applied a well-rotted compost 

 of horse manure and muck. Such an application will undoubtedly 

 tend to make the soil more acidic in its nature and thus antagonistic 

 to the development of the fungus. 



In addition to checking damping-off effectively, acid treatment at 

 the Bessey Nursery has resulted in the production of stock that aver- 

 ages fully an inch higher than nonacid-treated stock. At this nursery 

 another feature of the acid treatment is that it seems to kill the weed 

 seed and very greatly reduces the cost of weeding thereby. During 

 1912 the cost of weeding acid beds was $0.0044, while the cost of non- 

 treated beds was $0.0125 per square foot. 2 The extra cost of acid 

 treatment was $0,005 per square foot. The total cost of acid and 

 weeding was therefore $0.0094 per square foot, as compared to 

 $0.0125 for weeding only of nontreated beds. Thus the saving in 

 the cost of weeding at least fully offsets the increase in cost due to 

 acid treatment. 



A 1 per cent formaldehyde solution applied at the rate of three- 

 fourths of a gallon per square foot about a week before the seed 

 is sown has been shown x to be very effective in preventing damping- 

 off, but it is known that formaldehyde may kill seed wdiich is still 

 dormant. On the whole, the experience with formaldehyde at most 

 Forest Service nurseries has not been as satisfactory as with acid. 

 The formaldehyde, especially with sandy soils, must be applied two 

 or three weeks before seed are sown in order to avoid killing them. 



1 Gilford, C. M. " The Damping-off of Coniferous Seedlings." Vt. Agr. Exp. Sta. 

 BoL 157. 



2 Cost of acid treatment will be temporarily higher during the European war on ac- 

 count of increased price of acid. 



