Saturated hydraulic conductivity of a sandy loam under no-till and intensive tillage in a corn-soybean rotation

Authors: Jabro, Jalal - Jay; Stevens, William - Bart; Iversen, William - Bill; Sainju, Upendra; Allen, Brett

Submitted to: Soil Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/5/2023
Publication Date: 9/13/2023
Citation: Jabro, J.D., Stevens, W.B., Iversen, W.M., Sainju, U.M., Allen, B.L. 2023. Saturated hydraulic conductivity of a sandy loam under no-till and intensive tillage in a corn-soybean rotation. Soil Systems. 7,79. https://doi.org/10.3390/soilsystems7030079.
DOI: https://doi.org/10.3390/soilsystems7030079

Interpretive Summary: Saturated hydraulic conductivity (Ks) of soil is a measure of water movement into the soil surface and through the soil subsurface or permeability of soil when it is saturated. It is an important soil property that affects water movement and transport of chemicals in the soil. The most common physical properties affecting water movement into the soil surface and through the subsurface are pore size distribution, pore continuity, soil texture, soil structure, and total porosity. Tillage is one of the most effective farming management practices that can largely affect physical and hydraulic properties of the soil. It can influence plant available water capacity and soil water retention, then consequently affecting plant growth and crop production. In agricultural fields, soils are not uniform but rather are heterogeneous and their soil physical and hydraulic properties, including Ks, vary greatly in space and time and due to tillage manipulation practices. Knowing spatial variability in soil properties such as Ks is important for soil management and can aid farmers to manage their inputs of water and fertilizer across their farms. Based on our conflicting findings and those reported by previous studies, the effect of tillage on soil Ks measurements is still not fully understood due to profound natural soil variability and heterogeneity resulting from soil forming factors across agricultural fields. The inconsistency in Ks measurements may also be explained by the mechanical effect of tillage that considerably manipulates soil physical properties including pore size distribution, soil structure and total porosity.

Technical Abstract: The rate at which water movers into and through the soil is a critical factor affecting irrigation management. Farmers in the northern Great Plains (NGP) irrigated cropping systems are reducing tillage as they convert from conventional flood irrigation to sprinkler irrigation. Consequently, there is a need for information about the effect of tillage practices on soil hydraulic properties for crops growing under sprinkler irrigation in the NGP. A field study was conducted from 2014 to 2018 to assess the effect of no-tillage (NT) and conventional tillage (CT) on saturated hydraulic conductivity (Ks) of a sandy loam soil in a 2-yr corn (Zea mays L.)-soybean (Glycine max [L.]) rotation. In-situ Ks measurements were made 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) were generally not significantly impacted by tillage. Averaged over the 5-yr study, log Ks of 100 measurements were 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 (1.782 mm h-1) was significantly greater than in NT plots (1.272 mm h-1) in the 15-30 cm layer under corn, where Ks was 40.1% greater in CT than NT. Large values of coefficient of variation (CV %) of Ks measurements reflect the skewness of the frequency distributions, exhibiting 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 larger sample size per treatment are needed to lower spatial variability within treatments and validate the effect of tillage on soil hydraulic properties.