土壌のアンモニウム固定に就いて : III 福間土壌のアンモニウム固定

抄録

The purpose of this investigation was to find out a definite mineral in Fukuma soil causes the fixation of ammonium. The soil used has a property of fixing large amounts of ammonium as reported by the authors in the previous papers. The results of the investigation are as follows : 1. The ammonium is more adsorbed by ground soil in a ball mill than unground one, whereas the capacity of fixing ammonium by soil decreases remarkably by grinding. 2. In the six textual separates of the soil, the intermediate one i.e. fine sand has the highest capacity of fixing ammonium and the coarser or finer separates, the lower. 3. Sand separates consist of large amounts of quartz and moderately weathered feldspar and biotite, and small amounts of magnetite aud others. Among these minerals only an altered biotite was found to fix ammonium. 4. Several minerals belong to mica group, chlorites, so-called vermiculites and rocks including mica were examined on the fixing capacity. The lepidomelane from Iizuka town in Fukushima prefecture and two specimens of so-called vermiculite were found to have high capacity, and muscovite, biotite, sericite, chlorite, rocks bearing mica i.e. gneiss, schist and pegmatite examined have none. 5. From high content of water it may be assumed that the lepidomelane sample has suffered somewhat weathering. 6. Chemical composition of weathered biotite in the soil resembles closely to the so-called vermiculite, and they have higer contents of iron, potassium and sodium, and lower contents of magnesium and water than the vermiculitc. 7. It is concluded that the mineral in Fukuma soil causes the fixation of ammonium is so-called vermiculite which is making up of interstratified layers of mica and vermiculite.