CONTROL OF DAMPING-OFF 9 



30 days before seeding, the number of plants which lived was increased as follows: 

 beet by 176 percent, cabbage by 18 percent, cucumber by 450 percent, and lettuce 

 by 55 percent. It should be noted, as a basis of comparison with these results, 

 that damping-off was more severe in soil treated with formaldehyde 2 cc. per 

 square foot) 30 days before seeding than it was in untreated soil, for the treated 

 soil had, by that time, become heavily reinfested with soil fungi. Such treatment 

 with formaldehyde applied to soil before seeding gave good protection for about 

 5 days, some protection for about 11 days, but practically no protection if seeds 

 were sowed 11 days or more after soil treatment. 



Ammonium Hydroxide and Ammonium Sulfate 



Ammonium hydroxide and ammonium sulfate reduced Icsses caused by a root- 

 rot ot sugar beet if applied to soils having sufficiently high pH values (3); and 

 ammonium sulfate, with lime, has been successfully used in the protection of 

 cotton against a root-rot (16). 



Ammonium hydroxide was applied to a soil having pH values ot 6.0 or 7.1, the 

 latter value resulting from the earlier use of hydrated lime. Seeds were sowed 

 10 days after the application ol ammonium hydroxide, with the results shown in 

 Tables. 



Table 5. — Effects of Ammonium Hydroxide and Soil Reaction on the 

 Control of Damping-off 



Ammonium 

 Hydroxide' 



Relative Number of Plants Which Lived 



Percentages 

 Which Damped-off 



Beet Cabbage Cress Cucumber Pepper Beet Cress Cucumber 



pH Value of Soil Before Treatment, 6.0 



Nsne (check) 100 100 100 100 100 



10 cc 227 140 157 120 128 



16 cc 268 187 155 225 140 



20 cc 240 160 150 214 125 



pH Value of Soil Before Treatment, 7.1 



None (check) 100 100 100 100 100 



10 cc 237 163 182 158 128 



16 cc 260 139 156 172 145 



20 cc 218 133 158 209 153 



'In 1 quart of water per square foot. 



The only injury to growth was caused by 20 cc. and that was confined to cress 

 and cucumber in the scil with a pH value of 7.1. Ammoniuin hydroxide this 

 used controlled damping-off practically as well and improved stands practically 

 as much in a soil which, before treatment, had a pH value ol 6.0 as it did in a soil 

 which had a pH value of 7.1, although control of damping-off by the lightest 

 application, 10 cc, was slightly less good in the acid soil. 



In another experiment (see Table 6), ammonium hydroxide, 12 cc. (in 1 quart 

 water) per square foot, gave good results in soil with a pH value of 7.1, even when 

 seeds of beet were sowed immediately after soil treatment ; but for best results 

 with 16 cc, it was necessary to wait a few days before seeding. 



