Temporal changes in soil hydraulic conductivity in saturated and unsaturated fields
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Temporal changes in soil hydraulic conductivity in saturated and unsaturated fields Junko Nishiwaki1 · Robert Horton2 Received: 29 September 2019 / Revised: 11 June 2020 / Accepted: 19 June 2020 © The International Society of Paddy and Water Environment Engineering 2020
Abstract Soil hydraulic conductivity ( K ) is an important soil property that exhibits relatively large uncertainty. The temporal variability of K is often ignored when calculating water movement in soil. Various factors such as tillage, rain, temperature, wetting/ drying, soil surface crusting, solution concentration, and biological activity can influence field K . We investigated soil K in a central Iowa field as a function of time and tillage by using tension infiltrometer measurements with pressure head tension settings of 0 cm and − 3 cm. No clear relationship was found between bulk density ( 𝜌b ) and K . Path analysis was conducted to assess the contribution ratios and causal relationships between factors affecting K . The K values were influenced by physical impacts such as tillage, precipitation, and surface crusting with contributions of 24%, − 32%, and 49%, respectively, and with error of 60%. Soil surface crusting had a particularly large impact on saturated K . The maximum volume fraction influenced K . Earthworm activity that impacted the soil pore structure was also noticed in the field. Owing to this biological mechanism, no relationship was observed between 𝜌b and K . It is important to recognize the multiple combined effects of soil physical processes and biological activities when documenting K in field soils. Keywords Hydraulic conductivity · Temporal change · Tillage · Precipitation · Soil surface crust · Multiple combined effects
Introduction Soil hydraulic conductivity ( K ) is an important property related to water and solute movement, and it has spatial (e.g., Nielsen et al. 1973; Mohanty et al. 1994; Strock et al. 2001) and temporal (e.g., Angulo-Jaramillo et al. 1997; Alletto and Coquet 2009; Soracco et al. 2018) variability. Temporal changes can result from various mechanisms (Mapa et al. 1986; Angulo-Jaramillo et al. 1997; Azevedo et al. 1998; Hu et al. 2009; Alletto and Coquet 2009; Soracco et al. 2015, 2018). Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10333-020-00810-x) contains supplementary material, which is available to authorized users. * Junko Nishiwaki [email protected] 1
College of Agriculture, Ibaraki University, 3‑21‑1, Chuuo, Ami, Inashiki, Ibaraki 300‑0393, Japan
Department of Agronomy, Iowa State University, 2104 Agronomy Hall, 716 Farm House Lane, Ames, IA 50011‑1051, USA
2
Field K has been measured using various methods, such as infiltration methods, falling-head well tests, and pumping tests. Because measurements can be time consuming and laborious, K values are sometimes estimated using pedotransfer functions. Multidomain models have been used (Wilson et al. 1992; Durner and Flühler 1996; Gerke 20
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