Water Flux and Drainage from Soil Measured with Automated Passive Capillary Wick Samplers

Abstract

Various soil water samplers are used to monitor measure and estimate drainage water, fluxes and solute transport in the soil vadose zone. Passive capillary samplers (PCAPs) have shown potential to provide better measurements and estimates of soil water drainage and fluxes than other lysimeters.Twelve automated PCAPs with dimensions of 30 cm (This symbol is not available in html. Please view the pdf version.) 90 cm (This symbol is not available in html. Please view the pdf version.) 85 cm were designed and placed 90 cm below the soil surface in a Lihen sandy loam (sandy, mixed, frigid Entic Haplustoll). The PCAPs were installed to continually quantify the amount of drainage water and fluxes occurring below the rootzone of sugarbeet (Beta vulgaris L.) and malting barley (Hordeum vulgare L.) cropping system under 30 mm (low replacement) and 15 mm (high replacement) irrigation frequencies. Two TDR sensors were positioned above each PCAP to monitor soil water contents and gradients continuously. Drainage water was extracted, collected and measured periodically and samples were stored for further analysis. This design incorporated Bluetooth sensing technology to enable an automated datalogger to transmit drainage water data simultaneously every 15 minutes to a remote host. Real-time seamless monitoring of drainage water and fluxes was thus possible without the need of costly time-consuming supportive operations. Our PCAP design provided an accurate and convenient way to measure water drainage and flux in the vadose zone. Moreover, it offered a significantly larger area of coverage (2700 cm2) than similarly designed vadose zone fluxmeters. In the course of field testing over the last year we incorporated several additional enhancements, all of which we recommend for optimal performance.