Soil Water Content Sensor Response to Organic Matter Content under Laboratory Conditions

Studies show that the performance of soil water content monitoring (SWCM) sensors is affected by soil physical and chemical properties. However, the effect of organic matter on SWCM sensor responses remains less understood. Therefore, the objectives of this study are to (i) assess the effect of organic matter on the accuracy and precision of SWCM sensors using a commercially available soil water content monitoring sensor; and (ii) account for the organic matter effect on the sensor’s accuracy. Sand columns with seven rates of oven-dried sawdust (2%, 4%, 6%, 8%, 10%, 12% and 18% v/v, used as an organic matter amendment), thoroughly mixed with quartz sand, and a control without sawdust were prepared by packing quartz sand in two-liter glass containers. Sand was purposely chosen because of the absence of any organic matter or salinity, and also because sand has a relatively low cation exchange capacity that will not interfere with the treatment effect of the current work. Sensor readings (raw counts) were monitored at seven water content levels (0, 0.02, 0.04, 0.08, 0.12, 0.18, 0.24, and 0.30 cm3 cm−3) by uniformly adding the corresponding volumes of deionized water in addition to the oven-dry one. Sensor readings were significantly (p < 0.05) affected by the organic matter level and water content. Sensor readings were strongly correlated with the organic matter level (R2 = 0.92). In addition, the default calibration equation underestimated the water content readings at the lower water content range (<0.05 cm3 cm−3), while it overestimated the water content at the higher water content range (>0.05 cm3 cm−3). A new polynomial calibration equation that uses raw count and organic matter content as covariates improved the accuracy of the sensor (RMSE = 0.01 cm3 cm−3). Overall, findings of this study highlight the need to account for the effect of soil organic matter content to improve the accuracy and precision of the tested sensor under different soils and environmental conditions.

[1]  A. Fares,et al.  Irrigation water requirements for seed corn and coffee under potential climate change scenarios , 2016 .

[2]  Sonia I. Seneviratne,et al.  Comparison of four soil moisture sensor types under field conditions in Switzerland , 2012 .

[3]  Ali Fares,et al.  Dual Field Calibration of Capacitance and Neutron Soil Water Sensors in a Shrinking–Swelling Clay Soil , 2004 .

[4]  Finn Plauborg,et al.  In Situ Comparison of Three Dielectric Soil Moisture Sensors in Drip Irrigated Sandy Soils , 2005 .

[5]  A. Dégre,et al.  Soil-specific calibration of capacitance sensors considering clay content and bulk density , 2016 .

[6]  M. K. Eusufzai,et al.  Effect of Organic Matter Amendment on Hydraulic and Pore Characteristics of a Clay Loam Soil , 2012 .

[7]  Gaylon S. Campbell,et al.  Calibration and Evaluation of an Improved Low-Cost Soil Moisture Sensor , 2007 .

[8]  W. J. Rawlsa,et al.  Effect of soil organic carbon on soil water retention , 2003 .

[9]  Aaron A. Berg,et al.  Importance of soil organic carbon on surface soil water content variability among agricultural fields , 2014 .

[10]  Noman Islam,et al.  A review of wireless sensors and networks' applications in agriculture , 2014, Comput. Stand. Interfaces.

[11]  Steven R. Evett,et al.  Soil Material, Temperature, and Salinity Effects on Calibration of Multisensor Capacitance Probes , 2000 .

[12]  M. Safeeq,et al.  RESPONSE OF SELECTED SOIL PHYSICAL AND HYDROLOGIC PROPERTIES TO MANURE AMENDMENT RATES, LEVELS, ANDTYPES , 2008 .

[13]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[14]  Francesco Montesano,et al.  Calibration and performance of moisture sensors in soilless substrates: ECH2O and Theta probes , 2007 .

[15]  Scott B. Jones,et al.  Evaluation of Standard Calibration Functions for Eight Electromagnetic Soil Moisture Sensors , 2013 .

[16]  M. Baghini,et al.  A critical review of soil moisture measurement , 2014 .

[17]  Konstantinos X. Soulis,et al.  Performance Analysis and Calibration of a New Low-Cost Capacitance Soil Moisture Sensor , 2012 .

[18]  K. Uzoma,et al.  Comparison of three dielectric moisture sensors for measurement of water in saline sandy soil , 2008 .

[19]  Tanya Kunberger,et al.  Calibration of the 10HS Soil Moisture Sensor for Southwest Florida Agricultural Soils , 2013 .

[20]  Nunzio Romano,et al.  Soil moisture at local scale: Measurements and simulations , 2014 .

[21]  C. Corradini,et al.  Soil moisture in the development of hydrological processes and its determination at different spatial scales , 2014 .

[22]  Ali Fares,et al.  Temperature and Probe‐to‐Probe Variability Effects on the Performance of Capacitance Soil Moisture Sensors in an Oxisol , 2016 .

[23]  V. Polyakov,et al.  Calibration of a Capacitance System for Measuring Water Content of Tropical Soil , 2005 .

[24]  Mike Schwank,et al.  Simulated Effects of Soil Temperature and Salinity on Capacitance Sensor Measurements , 2007, Sensors (Basel, Switzerland).

[25]  M. Safeeq,et al.  Adjusting Temperature and Salinity Effects on Single Capacitance Sensors , 2009 .

[26]  G. Rallo,et al.  Assessing Field and Laboratory Calibration Protocols for the Diviner 2000 Probe in a Range of Soils with Different Textures , 2016 .

[27]  Soil texture and salinity effects on calibration of TDR300 dielectric moisture sensor , 2013 .

[28]  Anthony R. Dexter,et al.  Soil physical quality: Part III: Unsaturated hydraulic conductivity and general conclusions about S-theory , 2004 .

[29]  Junhong Zhang,et al.  Field‐Specific Calibration and Evaluation of ECH2O EC‐5 Sensor for Sandy Soils , 2014 .

[30]  Ramchand Oad,et al.  Comparison of Laboratory and Field Calibration of a Soil-Moisture Capacitance Probe for Various Soils , 2012 .

[31]  Ali Fares,et al.  Temperature-Dependent Scaled Frequency: Improved Accuracy of Multisensor Capacitance Probes , 2007 .

[32]  G. Richard,et al.  Complexed organic matter controls soil physical properties , 2008 .

[33]  R. Knight,et al.  Soil Moisture Measurement for Ecological and Hydrological Watershed‐Scale Observatories: A Review , 2008 .

[34]  Ali Fares,et al.  Improved Calibration Functions of Three Capacitance Probes for the Measurement of Soil Moisture in Tropical Soils , 2011, Sensors.

[35]  Michael D. Dukes,et al.  Effect of Temperature and Salinity on the Precision and Accuracy of Landscape Irrigation Soil Moisture Sensor Systems , 2015 .