Saturated Hydraulic Conductivity Measurements in a Loam Soil Covered by Native Vegetation: Spatial and Temporal Variability in the Upper Soil Layer

George Kargas,Paraskevi A Londra,Kyriaki Sotirakoglou

doi:10.3390/geosciences11020105

George Kargas, Paraskevi A Londra + Show 1 more

Open Access

https://doi.org/10.3390/geosciences11020105

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Journal: Geosciences	Publication Date: Feb 22, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: Agricultural University of Athens

Abstract

Saturated hydraulic conductivity (Ks) of soil, especially of the upper soil layer, is a basic parameter for modeling water infiltration and solute transport in the soil. In the present study, spatial and temporal variability of Ks in the upper soil layer of a loam soil, which was covered by native vegetation for 20 years and had not undergone any cultivation treatment, is investigated. Saturated hydraulic conductivity of 76 undisturbed soil samples, taken twice a year at the dry (37 soil samples) and rainy periods (39 soil samples), was measured using a constant head method. The study reveals that Ks values exhibit significant spatial variability over the two time periods of measurement and follow a lognormal distribution with a coefficient of variation greater than 70%. On the contrary, there was no statistically significant seasonal variability of Ks between summer (dry period) and winter (rainy period) sampling (p > 0.05), and, therefore, there was no significant temporal variability of Ks. The outcome of this study indicated that hydrological models have to include more process understanding in terms of natural variability.

Highlights

Saturated hydraulic conductivity (Ks ) expresses the soil’s ability to transport water under saturated conditions and is a key parameter in water movement and solute transport models in soil
Hydraulic conductivity depends on soil structure, which could vary in both space and time
Kss was measured measured in in cm cm min min. It appears that experimental Ks values showed high spatial variability in both dry and rainy periods with Coefficient of Variation (CV) values of 72.15% and 77.65%, respectively, following lognormal distributions, while there was no significant temporal variability of Ks (p > 0.05)

Summary

Introduction

Saturated hydraulic conductivity (Ks ) expresses the soil’s ability to transport water under saturated conditions and is a key parameter in water movement and solute transport models in soil. Any change in the surface soil layer caused by natural factors, such as rainfall, growth and decay of plant roots, shrinking and swelling, or human interventions, such as cultivation treatments, wheel-traffic compaction, etc., can lead to changes in soil porosity These changes can seriously affect hydraulic conductivity and soil water storage. Strudley et al [25] proposed that the data collection should be strengthened in order to clarify spatial and temporal trends, and that seasonal/annual measurements should be performed to clarify short-term changes He indicated that other secondary factors may affect. Among those secondary factors, there are some related to soil biological activity, which is relatively unexplored and could partly explain the observed temporal variability of Ks. the growth of roots, the decomposition of dead roots, and the earthworms affect the networks of macro-pores, which can significantly change the Ks in space and time [26,27,28]. The saturated hydraulic conductivity measurements on undisturbed soil samples taken twice a year, during the dry and rainy periods (summer and winter), were conducted in the laboratory using a constant head method

Study Area and Sampling

Saturated Hydraulic Conductivity Determination Method

Results and Discussion

Probability

Boxplot andof

Conclusions