Soil health responses to terrace construction - part I

• Terracing results in a loss of soil health with a significant shift in soil textural classes. • Terrace construction process leads to intermixing and redistribution of the soil layers. • Terrace construction increased the bulk density of subsurface soil layers. • Construction of terraces leads to a reduction of soil enzyme activity and total carbon. • Total nitrogen and permanganate oxidizable carbon increased after terrace construction. Terraces are widely used to mitigate soil erosion on sloping terrains, but their construction involves extensive soil disturbance that may affect soil condition and health. The objective of this study was to evaluate changes in soil properties before and after the construction of broad-based terraces. Geo-tagged soil samples were collected from three topographic positions (shoulder, backslope, and footslope) at four depths (0-15, 15-30, 30-45, and 45-60 cm). Post-construction, both sand and clay content increased by 31.7 g kg -1 , soil temperature increased by 1.7 °C, permanganate oxidizable carbon increased 12%, total nitrogen increased 0.06 g kg -1 , and bulk density (BD) at 30-60 cm increased 7-13% compared to pre-terrace construction soil samples. In contrast, BD decreased by 8-23% in the 0-30 cm layer for post-terrace construction soil samples. Terrace construction did not significantly affect volumetric water content or electrical conductivity at the surface soil layer (0-15 cm). However, it negatively impacted wet aggregate stability (15-19%) and total carbon (0.54 g kg -1 ) compared to pre-construction values along with 60.3 g kg -1 decrease in silt content. Additionally, notable reductions in post-terrace construction soil samples for surface soil layers were observed for soil enzyme activity, including acid phosphatase (26%), β-glucosidase (45%), β-glucosaminidase (47%), and arylsulfatase (50%). These findings indicate that terrace construction substantially alters soil condition across the profile due to soil mixing and redistribution. Long-term monitoring is necessary to determine whether these changes persist or if soils can recover with improved management systems.