The Long-term Variations and Influencing Factors of Soil Saturated Hydraulic Conductivity in Terraces on the Loess Plateau

[Objective] The long-term variations of soil saturated hydraulic conductivity (Ks) and its primary controlling factors in terraces on the Loess Plateau were explored. [Methods] Terraces were selected for three land use types, i.e. farmland, orchard, and grassland, with slope designated as the control. Soil samples were collected from slopes and terraces with construction ages of 7, 20, 30 and 40 years to determine the Ks and soil physicochemical properties. The Kruskal-Wallis H test, Spearman correlation analysis, and partial least squares path model (PLS-PM) were conducted to examine the impact of terrace construction on Ks and its temporal variations, as well as the influencing factors. [Results] (1) The Ks of terraces under different land use types exhibited varying patterns with increasing ages of terrace construction. The Ks of farmland increased continuously with construction age of 7, 20, 30 and 40 years, increasing from 0.18 mm/min to 0.28 mm/min, with a growth rate of 55.56%. The Ks of orchard increased with the increase of construction years firstly, then showed a decreasing trend after 30 years, and the Ks of orchard with a construction age of 30 years was significantly higher than that of orchard with a construction age of 7 years, increasing from 0.12 mm/min to 0.35 mm/min, with a growth rate of 191.67%. The Ks of grassland increased with the increase of construction years firstly, then remained relatively stable after 20 years, and the Ks of grassland with a construction age of 20 years was significantly higher than that of grassland with a construction age of 7 years, increasing from 0.14 mm/min to 0.31 mm/min, with a growth rate of 121.43%. (2) The primary factors influencing Ks included soil particle size distribution, soil bulk density, and mean weight diameter of aggregates, with the path coefficients being -0.431, -0.561 and 0.226, respectively. [Conclusion] The variation in the impact of terrace land use types on soil properties resulted in varying patterns of Ks with increasing ages of terrace construction. The results can provide a basis for the subsequent management of terraces and the development of efficient dryland farming.