Abstract
The amount of roots, physical (dry bulk density, pF, soil hardness etc.) and chemical (Cl-, SO42-, Na etc.) properties of soils in each soil profiles were investigated in A6 field (natural plot, where Phragmites australis (Cv.) Trin. ex Steud. is still alive in the field) and A10 field (hay field, where grass is cultivated continuosly without plowing) of Hachirogata Central Polder, to elucidate the differences in the effects of Phragmites and grass on the drying of Hedoro ground. The results obtained are as follows.
1. The amount of rhizomes and roots of Phragmites are about 83% in the layers between 20cm and 100cm deep of natural plot. On the other hand, the amount of roots of grass is about 90% in the layers between surface and 20cm deep of hay field.
2. In the layers between surface and 20cm deep of hay field, the dry bulk density increases and water retentivity becomes lower, compared to those in the natural plot. In the layers 50cm and 100cm deep of natural plot, the dry bulk density increases remarkably and water retentivity becomes lower, compared to those in the hay field.
3. The volumetric water content and hardness index of the soils in the natural plot and hay field are nearly proportional to the dry bulk density in the region between about 0.35 and 0.6g/cm3 respectively.
4. The depth of the invasion of gaseous phase in the natural plot is greater than that in the hay field.
5. Cl- content of the soils in the natural plot and hay field are 29ppm and 358 ppm in the layers between surface and 100cm deep respectively.
6. In the layers between 30cm and 100 cm deep, SO42- content of the soil in the natural plot is about three times as much as that in the hay field.
7. Na and Mg content of soils in the natural plot become lower in layers more than 70cm below the ground surface, compared to those in the hay field.
8. EC (mS/cm) of soil in the natural plot is very small in layers more than 70cm below the ground surface, compared to that in the hay field.
