Abstract
Soil hydraulic properties play an important role in determining the level of crop productivity and the extent of environmental loading. Consequently, measurement of near-saturated soil hydraulic conductivity (K(h)) by tension infiltrometer (TI) is an interesting technique. To provide reference values for near-saturated K(h) in arable mineral topsoils of Finland and to investigate variability in these values caused by tillage, antecedent soil moisture content and earthworm burrows, field measurements were conducted in south-western and central-eastern Finland using the TI technique, at supply pressure head –6, –3, and –1 cm. The range of near-saturated K(h) values obtained was 0.02–12.6 mm h-1 at –6 cm, 0.30–85.9 mm h-1 at –3 cm, and 2.55–250 mm h-1 at –1 cm. At –6 cm pressure head, clay soils tended to show lower values than coarser-structured soils, but the order was reversed at –1 cm. The spatial variation in near-saturated K(h) was moderate and was exceeded by the temporal variation.
Highlights
The flow of water into and within soil governs several critical ecosystem functions, including soil moisture storage, groundwater recharge, regulation of gas flows, and transport of solutes and particulate materials (e.g. Nielsen et al 1986, Adhikari and Hartemink 2016)
In situ measurements of near-saturated soil hydraulic conductivity (K(h)) using the tension infiltrometers (TI) technique were performed on fine- and coarser-textured arable topsoils in south-western and central-eastern Finland in three consecutive years
The range of values obtained at the soil surface was 0.02−12.6 mm h-1 at −6 cm supply pressure head, 0.30−85.9 mm h-1 at −3 cm, and 2.55−250 mm h-1 at −1 cm
Summary
The flow of water into and within soil governs several critical ecosystem functions, including soil moisture storage, groundwater recharge, regulation of gas flows, and transport of solutes and particulate materials (e.g. Nielsen et al 1986, Adhikari and Hartemink 2016). The capacity of a soil for water infiltration, i.e. soil hydraulic conductivity, is generally determined in saturated state (all pores water-filled) by monitoring the flow rate under a constant or falling positive hydraulic head (Angulo-Jaramillo et al 2016). During recent decades, measurements of unsaturated or near-saturated soil hydraulic conductivity by tension infiltrometers (TI) have been extensively used (Angulo-Jaramillo et al 2000, Jarvis et al.2013). In the method, unconfined measurements of infiltration rates are carried out at different negative pressure heads relative to atmospheric pressure applied with minimum disturbance on the same soil surface (Ankeny et al 1991, Angulo-Jaramillo et al 2016). The measured infiltration rates can be converted to hydraulic conductivity values using Wooding’s theory of infiltration from a circular source (Wooding 1968)
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