An Automated Vacuum Extraction Control System for Soil Water Percolation Samplers

Abstract

A vacuum applied to soil water percolation samplers permits collection of both macro-and matrix-pore liquids. Performance of these field samplers is improved when the extraction vacuum is adjusted in accordance with the tension in the surrounding soil. This is particularly important when monitoring a network of spatially distributed samplers and for samplers installed in medium to fine textured soils. We designed a vacuum extraction system to more efficiently collect vadosezone soil solution samples. A single vacuum pump, vacuum tank, and air dryer provided a vacuum supply for 12 soil water sampling sites via a branching polyethylene pipe network. A vacuum controller containing two inexpensive pressure transducers, a voltage regulator, relay, and solenoid valve was developed and tested for field installation. Data loggers operated the controllers, monitored extraction vacuum and ambient soil water potential, and adjusted relative vacuum at each percolation sampling site. The automated vacuum controllers successfully maintained sampler extraction pressures at levels proportional to ambient soil water potential and provided the added benefit of recording the pressure values for use in subsequent data interpretation.

An experimental and numerical study on flow and transport in a field soil using zero‐tension lysimeters and suction plates

“…Vacuum solution samplers, like suction cups or suction plates (Litaor, 1988), collect an approximation of the flux concentration when operated in a continuous mode. A system where the suction is automatically adjusted to a target value measured with tensiometers in the natural soil profile seems to be favourable to minimize disturbances of the natural flow field during transient, unsaturated flow (van Grinsven et al, 1988;Brye et al, 1999;Lentz & Kincaid, 2003;Barzegar et al, 2004;Kosugi & Katsuyama, 2004;Siemens & Kaupenjohann, 2004). The collection of leachate by suction plates is more representative compared to suction cups due to a larger surface area.…”

Mineral Fertilizer and Manure Effects on Leached Inorganic Nitrogen, Nitrate Isotopic Composition, Phosphorus, and Dissolved Organic Carbon under Furrow Irrigation

“…1.2 m, directly below one of the monitored furrows in each plot (Lentz and Kincaid, 2003). Each plot's three soil water samplers were spaced approximately 0.7 m apart and were located approximately midway down the furrow length, a location that receives near-average infiltrated irrigation water.…”

“…Each plot's three soil water samplers were spaced approximately 0.7 m apart and were located approximately midway down the furrow length, a location that receives near-average infiltrated irrigation water. Samplers were installed such that an undisturbed column of soil extended from within the sampler, through its open top, and up to the soil surface (Lentz and Kincaid, 2003). Thus, water flowing down macropores present in the undisturbed soil would be collected in the sampler, as would matrix-pore flow.…”

“…The vacuum was adjusted for in situ soil matric potential to maintain parallel, vertical flow lines in the soil above and adjacent to the sampler. This design, which produced valid measures of soil water flux rates and leachate solute concentrations under continuous extraction, was described previously (Lentz and Kincaid, 2003;Lentz, 2006;Lentz and Lehrsch, 2014), along with details of the vacuum extraction system and field installation.…”

Measurement of Fertilizer Leaching from the Root Zone Using an Automated Infiltration Soil Water Sampler in an Unsaturated Sandy Field

“…Although many soil water-sampling methods are available, no single sampling technique has been found to be suitable under all the conditions (Barzegar et al 2004). A direct soil water sampler with a suction-controlled lysimeter consisting of a porous plate or a porous cup connected to an automated vacuum system and tensiometers was developed (van Grinsven et al 1988;Lentz and Kincaid 2003;Kosugi and Katsuyama 2004). Suction-controlled lysimeters are able to collect infiltration water effectively.…”