Soil fertility, texture, and apparent electrical conductivity responses to terrace construction

Many agricultural landscapes within the Midwest United States, particularly those with highly erodible soils and intensive row crop production, are characterized by sloping terrains. To facilitate cultivation while minimizing soil erosion, terracing is often implemented. Terrace construction involves extensive manipulation of the soil profile, which can alter soil fertility and texture. This study evaluated changes in Mehlich-III extractable nutrients, soil texture, and apparent electrical conductivity (ECa) following the construction of eight broad-based terraces in a conventional row crop field. Georeferenced soil samples were collected before and after terrace construction from three topographic positions (TP; shoulder, backslope, and footslope) at four depths (0 to 15, 15 to 30, 30 to 45, and 45 to 60 cm). After terrace construction, total exchange capacity, sulfur, magnesium, potassium, sodium, and iron availability significantly increased, whereas soil pH, calcium, and boron decreased. Mehlich-III extractable nutrients were significantly higher at footslope positions compared to the shoulder position following terrace construction. A significant soil textural shift was observed, in which sand and clay content both increased by 32 g kg−1, while silt decreased by 60 g kg−1. There were 19% to 36% reductions in four ECa readings (ECa-H0.5, ECa-H1, ECa-V0.5, and ECa-V1) recorded by an electromagnetic induction device. Principal component analysis separated pre- and post-terracing values by ECa responses, while also highlighting fertility and texture gradients across TPs and the depth of soil sample collection. These findings suggest that terracing alters soil extractable nutrients, texture, and ECa through soil mixing and redistribution. Long-term monitoring is recommended to determine the persistence of these soil changes in the modified landscape.