Saturated Hydraulic Conductivity of a Sandy Loam under No-Till and Intensive Tillage in a Corn–Soybean Rotation

Tillage management practices have a dynamic impact on soil hydraulic properties and processes. There is a need for information about the effect of tillage practices on soil hydraulic properties for crops growing under sprinkler irrigation in the northern Great Plains. A long-term study was conducted from 2014 to 2018 to examine the effect of no tillage (NT) and conventional tillage (CT) on the saturated hydraulic conductivity (Ks) of a sandy loam soil in a two-year corn (Zea mays L.)–soybean (Glycine max L.) rotation. In situ Ks measurements were taken in the center of crop rows within NT and CT plots using a pressure ring infiltrometer at the soil surface (0–15 cm) and a constant head well permeameter at the subsurface (15–30 cm). Results indicated that Ks values were well described by a log-normal distribution at both depths. Results showed that logarithmic Ks (log Ks) was not significantly impacted by tillage. Averaged over the five-year study, the log-transformed Ks of 100 measurements was not significantly affected by tillage in the surface layer under either corn or soybean nor in the subsurface layer under soybean. However, the mean soil log Ks in CT plots (1.784 mm h⁻¹) was significantly greater than that in NT plots (1.186 mm h⁻¹) in the 15–30 cm layer under corn, while Ks was nearly 50% greater in CT than in NT. Large values for the coefficient of variation (CV%) of Ks measurements exhibited significant spatial variations of Ks among plots within each tillage treatment at both the soil surface and subsurface layers under corn and soybean. Thus, more studies under different soils and cropping systems with a larger sample size per treatment are needed to lower spatial variability within treatments and validate the effect of tillage on soil hydraulic properties.