Acetic Acid and Pyroligneous Acid in Comparison with Formaldehyde as Soil Disinfectants ^

Formaldehyde is one of the most commonly used of soil disinfectants. Its efficacy against fungi in the soil is well established, but it has at least two faults. The cost of the treatment is relatively high and the time which must be allowed to elapse between treatment and seeding, if the treatment is not to injure germination, is sometimes objectionable. The principal object of the work here described was to find a soil disinfectant as ejBFective against fungi, lower in cost, and less injurious to seeds than is formaldehyde. In earlier experiments, the results of which have been described by the writer,^ LO to L2 per cent acetic acid used as a soil disinfectant was found to protect seedhngs from damping off. Similar results with acetic acid as a soil disinfectant have since been secured by other investigators.^ * The evidence presented in this paper verifies the conclusions previously reached in regard to acetic acid and serves as a basis for comparing acetic acid, pyroligneous acid, and formaldehyde as soil disinfectants. In the present paper various dilutions and rates of application of acetic acid, pyroHgneous acid, and formaldehyde are compared with each other as regards prevention of damping off (caused by species of Pythium and Rhizoctonia), effect on seed germination, and effect on growth (dry weight) of plants.