1992 Volume 63 Issue 6 Pages 669-676
The procedures of upland reclamation with backslope cutting and foreslope filling (BCFF) include 1) removing and storing the A horizon layer, 2) cutting and filling to create wide and gently sloping fields by grading, and 3) replacing the stored top soil evenly to create an Ap horizon. The procedures 1) and 3) are called surface layer treatment (SLT). We investigated soil physical properties of upland which had been reclaimed with BCFF, and compared these with undisturbed soil (UDS) and upland soil which had been reclaimed from original slopes about 20 years ago (FRU). 1) A comparison of the bulk density (BD), the humus contents and the thickness of each layer of the soils showed that the SLT soil layer (SLTS) is assumed to have been mainly derived from the A and B horizons of UDS. 2) The BD of SLTS just after SLT increases, and the coarse pore volume (CPV ; water head : 0-63 cm) and the readily available water holding pore volume (RAPV ; water head : 63-1000 cm) decreases, compared with the A and B horizon of UDS. The basic intake rates (IB) measured by the cylinder method just after SLT are 0 m h^<-1>, and far less than that of UDS and FRU. These suggest that SLTS was compacted and smeared during SLT. 3) Subsoiling just after SLT softened the soil materials near the track of the chisel and the standard of pan-breaker (decrease in BD and increase in CPV). There was no such softening between the passing tracks. Immediately after the subsoiling, IB varied from nearly the value just after SLT to about 1.4 m h^<-1>. 4) Harrowing and ;lowing decreased BD and soil hardness and increased CPV of the upper SLTS to that of the A horizon of UDS, but RAPV was not increased. 5) The soil structural changes caused by smearing and compaction during the reclamation processes with BCFF are consistent with the results of shrinkage tests, and were visualized with the micro morphology of soil thin section samples.
