抄録
Among various methods of extracting organic phosphorus from soil, the digestion procedure with 1〜2% NaOH solution has been found to be most effective (see table 1). Of NaOH method, many factors were investigated for the object of getting more yield than ever (see table 2〜5,fig. 1〜2). Depending on the results of investigation, a new quantitative method was proposed by authors as follows : 1 gram of soil, air-dried and ground to pass through 50 mesh siebe, was leached on a filter paper with 1% HCL solution until no more exchangeable Ca is detected. The leachate was filled up to 100 c.c. Leached soil was transfered to a centrifuger tube (50 cc in volume) with 10 cc of 1% NaOH solution, and digesed for 1 hour at 60° in the water bath. After the digestion, the tube was brought to be centrifuged, and the supernatant solution was obtained as a first extract. Second extract was then obtained by digesting the soil in the tube with 10 cc of 2% NaOH solution for 2 hours at 90° and centrifuging. The two extracts were combined, filling up to 100〜250 cc. Of the above extract, added with 1% HCl leachate, phosphorus in both forms, total and inorganic, was determined respectively. And organic phosphorus was got by substracting the amount of inorganic phosphorus from that of total phosphorus. After the results of comparison to the other methods, the above method, proposed by authors, seems to extract oaganic phosphorus from soils in the highest amount (see table 6), and to be manipulated fifth times more speedy than the method of PEARSON.
