Abstract
Pyroligneous acid (wood vinegar) can be collected easily as a by-product of charcoal making which is one of common manufacturings in Japanese forestry villages and is effective as a soil disinfectant in forestry nurseries according to NORARA'S investigations.
The author previously reported that the acid was toxic upon spore germination and mycelial growth of some plant pathogens not only as a drench but also as a fumigant and penetrated into the soil considerably and these characters might be associated with the disinfectant effect of the acid in the soil. The present paper dealt with some researches of microbial succession on the upper layer (0_??_5cm. depth) of the treated soils for about 1 year after the drenching with the acid by aid of the dilution plate method.
The main results observed on the treated soils comparing to the untreated were as follows:
1. Numbers of fungi decreased considerably at immediate several days after the drenching. Following this temporary depression there was a pronounced increase in the total numbers within 2 weeks and the high population was kept even at 1 year later.
2. Numbers of bacteria decreased at first, then increased conspicuously by 2 weeks after the drenching like that of the fungi, but by 3 months, they droped to the normal level.
3. Actinomycetes also reduced in numbers by the drenching and were thought to be not active in the soil again even at 1 year later. 4. Dominant fungi on the treated soils were Penicillium janthinellum series, P. citrinum series, P. oxalicum series and Trichoderma viride though these species were also detected considerably in the untreated soils.
5. Penicillium javanicum series were detected considerably from the treated soils in the following periods, elapsed about 3 months after the drenching.
