Swine manure transport measurements in cracking soils using time domain reflectometry

摘要

Potential groundwater quality degradation as a result of swine manure application in agricultural areas remains a serious environmental concern. Hence, studies on the potential use of modern nondestructive instrumentation techniques to monitor and predict swine manure movement in soils are of utmost importance. This study was conducted to test the applicability of time domain reflectometry (TDR) in monitoring swine manure transport in cracking soils. Field experiments were conducted in nonweighingtype lysimeters with Nicollet silt loam using TDR probes ranging in length from 0.15 to 0.60 m, connected to a multiplexer and a cable tester A short pulse of swine manure was applied at the surface of the presaturated lysimeter and the experiments wereperformed under steady saturated flow conditions at a constant head. Effluent samples were collected from the bottom of the lysimeter at regular intervals equivalent to 1/40 pore volumes and analyzed for electrical conductivity. The effluent and waveformdata were consequently transformed into relative residual mass breakthrough curves (BTCs). Results indicated a relatively fair agreement between the relative residual mass BTCs from TDR and effluent data. Despite the occurrence of preferential flow dueto soil cracking, which was depicted by an early breakthrough of swine manure with EC peaking at 0.12 to 0.25 pore volume, the TDR data still yielded fairly realistic relative mass breakthrough curves. The results of this study demonstrated some potential in using TDR to predict swine manure transport in soils.