Location: Agricultural Systems ResearchTitle: Field performance of three real-time moisture sensors in sandy loam and clay loam soils
Submitted to: Archives of Agronomy and Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2017
Publication Date: 10/26/2017
Citation: Jabro, J.D., Stevens, W.B., Iversen, W.M. 2017. Field performance of three real-time moisture sensors in sandy loam and clay loam soils. Archives of Agronomy and Soil Science. 64(7):930-938. https://doi.org/10.1080/03650340.2017.1393528.
Interpretive Summary: Increasing demands on scarce water resources in the western U.S. along with negative environmental impacts linked to over-irrigation require more efficient irrigation management. Accurately monitoring soil moisture is critical if water is to be applied with maximum efficiency but irrigators in the northern Great Plains lack information about which of the available soil moisture sensors are most effective for their specific crops and soil types. ARS researchers at Sidney, Montana evaluated three commercially available sensors on sandy and clay soil types and determined that each would have to be calibrated for specific soil conditions in order to provide accurate volumetric soil water measurements. However, all sensors produced similar trends in relative soil moisture changes over time. The researchers concluded that, even without soil-specific calibration, all three sensor provide reliable information that can improve irrigation decisions based on sensor output combined with visual observations of crop and soil conditions. Information from this research will help irrigators conserve water resources and optimize crop productivity while protecting environmental quality.
Technical Abstract: The study was conducted to evaluate HydraProbe (HyP), Campbell Time Domain Reflectometry (TDR) and Watermarks (WM) moisture sensors for their ability to estimate water content based on calibrated neutron probe measurements. The three sensors were in-situ tested under natural weather conditions over a 3-yr period in a sandy loam and clay loam soils planted to grass. The HyP, TDR and WM sensors were evaluated for their ability to estimate soil moisture contents by comparing their outputs with those of NP measurements. Results showed that HyP, TDR and WM provided different estimates of soil moisture contents in both soils. Nevertheless, our work suggests that soil moisture sensors including those used in this study can be made suitable for irrigation scheduling without in-situ calibrations by simply setting the upper and lower irrigation trigger limits for each sensor and each soil type. The upper trigger point occurs directly after irrigation event (near field capacity) and the lower trigger point is based on about 50% depletion of available water in the crop rootzone and is occurs prior to irrigation refill. This approach can significantly help irrigators to achieve their irrigation scheduling and productivity goals without consuming any time on-site or soil specific calibrations.