抄録
Detop cylinder made of refuse fire extinguisher as reaction vessel for acetylene reduction assay was reversely inserted into upland field soil covered with plants. Acetylene corresponding to about 10% (v/v) and 1 ml of propane were introduced into the vessel. Then, the above gases existed in the vessel and ethylene formed from acetylene were periodically measured. The results obtained were as follows. 1. Aerial volume of the vessel inserted into field was easily calculated from the dilution ratio of the introduced propane at the beginnig of the experiment. 2. The leakage of the inner gases from the vessel was presumedly determined through the decrement of propane as guide gas. 3. The reduction of acetylene to ethylene was found to proceed linearly with same rate until the oxygen pressure in the vessel decreased to about 10%. 4. According to the above technique, the acetylene reducing activity was observed to rank in higher order of alfalfa, white clover, common vetch grasslands. 5. From this investigation, the above devised method seemed to be useful on the non-destructive determination of nitrogen fixation in upland plants and fields.
