Abstract
The performance of the Irrometer 200SS Watermark granular matrix sensor (WM), John Deere Field Connect (JD-v2) probe, and Delta-T PR1-capacitance (PR1-C) probe were evaluated against a Troxler 4302 neutron gauge (NG) for in-season field volumetric water content (θ v) measurements at two soil depths in a Hastings silt loam soil at the University of Nebraska-Lincoln/Institute of Agriculture and Natural Resources South Central Agricultural Laboratory (SCAL) near Clay Center, Nebraska. The performances of the sensors were investigated over three years (2011-2013) under various water, nutrient, and crop management practices. The WM sensors performed best when using a field-calibrated soil water retention curve (SWRC) [root mean square difference (RMSD) = 0.024 m3 m-3] as compared to a SWRC developed from a pedotransfer function (RMSD = 0.070 m3 m-3). The WM sensors using a previously developed SWRC for the experimental field resulted in RMSD values less than 0.05 m3 m-3 when compared to the NG-measured θv at all depths and years. The JD-v2 probes underestimated θv in the dry range and overestimated θv in the wet range, which resulted in regression slopes and intercepts for the 0.30 and 1.0 m soil depths that were significantly different from unity (i.e., 1.0) and zero (p0.05 < 0.05), respectively. However, the performance of the JD-v2 probes improved in 2013 from RMSD values of 0.066, 0.068, and 0.067 m3 m-3 when using the manufacturer's calibration to 0.043, 0.033, and 0.038 m3 m-3 for the 0.30, 1.0 m, and pooled soil depths, respectively, after calibrating the JD-v2 probes using the 2012 regression responses. The PR1-C probe-estimated θv regression coefficients were also significantly different from unity and zero (p0.05 < 0.05), respectively, and the resulting RMSD values ranged from 0.077 to 1.133 m3 m-3 . In general, the WM and JD-v2 sensors followed the NG total water (TW) trends at all irrigation levels; however, the PR1-C probe was inconsistent and at times estimated unrealistic TW amounts. While there are limitations and concerns for each sensor technology, the results suggest that the WM and JD-v2 sensors can be used to monitor soil moisture to enhance irrigation management following field calibrations. Furthermore, development of soil-specific field calibration curves for individual soil depths is strongly recommended to enhance the performance of each sensor type and improve the accuracy of in-season field θv measurements.
Original language | English (US) |
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Pages (from-to) | 649-665 |
Number of pages | 17 |
Journal | Transactions of the ASABE |
Volume | 58 |
Issue number | 3 |
DOIs | |
State | Published - 2015 |
Keywords
- Capacitance probe
- Electrical resistance sensors
- Neutron gauge
- Soil moisture sensors
- Soil water retention curve
- Water content
ASJC Scopus subject areas
- Forestry
- Food Science
- Biomedical Engineering
- Agronomy and Crop Science
- Soil Science