Abstract: Long-term mechanical compaction could affect soil physical and hydraulic properties. These changes have further influence on the strength of soil preferential flow, but there is no consensus on such effect. To investigate the effects of long-term mechanical compaction on soil pre-ferential flow, we set three plots in each of the margin area (continuous compaction area, CC) and normal farming area (CK) in the Linze oasis croplands, and carried out a dye tracer experiment using the brilliant blue FCF solution. We measured soil bulk density, total soil porosity, and soil saturated hydraulic conductivity. Our results showed that long-term mechanical compaction had no effects on soil physical and hydraulic properties in the plow layer (0-20 cm), but had significant effects in the plow pan (20-60 cm) (P<0.05). Mechanical compaction increased soil bulk density by 10.8%, and decreased total soil porosity and soil saturated hydraulic conductivity separately by 11.9% and 32.3% at the 20-60 cm depth. Long-term mechanical compaction significantly affected the characteristics and strength of soil preferential flow. Lateral flow in continuous compaction area was significantly different from the macropore flow in normal farming area. The strength of soil preferential flow in continuous compaction area was also significantly greater than that in normal farming area (P<0.05), which was mainly related to the maximum infiltration depth (P<0.05). Our results indicated that long-term mechanical compaction significantly affected the soil physical and hydraulic properties in the plow pan and enhanced the strength of soil preferential flow.

Key words: Lake Taihu, ecosystem, Ecopath model, structure and function.