Date of this Version
Sharma, Kiran (2019). Performance and Operational Feasibility of Soil Moisture Sensors in Silt Loam and Loamy Sand Soils (Masters Thesis). University of Nebraska-Lincoln.
Accurate soil moisture measurement plays a crucial role in optimum irrigation management, quantification of crop water use and resolution of soil water balance, besides numerous other applications. Numerous sensors exist to estimate soil moisture and due to their diverse principles of operation, they are subject to varying levels of errors and uncertainties. Thus, prior to their use, the sensors have to be comprehensively assessed for their performance so as to evaluate the degree and nature of inaccuracy as well as the limits to their applications.
In this research, nine commercially available soil moisture sensors (CS655, CS616, 10HS, 5TE, EC-5, Teros 21 (MPS-6), SM150, TDR315L (Acclima) and JD Probe) were evaluated in silt loam and loamy sand soils. These sensors were investigated for their performance under two different orientations, i.e., vertical and horizontal. These investigations were conducted for two growing seasons (2017 and 2018) at South Central Agricultural Laboratory (an irrigated row crop site with maize-soybean rotation) and Central City (a rainfed pasture).
In the first chapter of this thesis, performance statistics for various sensors were quantified under factory calibrations (F.C.) during 2017. To account for the uncertainty associated with estimating volumetric water content (θv), calibration functions were developed and were validated using independent datasets collected during 2018. In the second chapter, the suitability of the sensors to report (a) total soil water (TSW); (b) actual evapotranspiration (ETc); and (c) irrigation triggers (IT) was assessed, which is rarely addressed in the literature. Finally, in the third chapter, we proposed a step-by-step guide that aimed at appropriate sensor selection by users with widely varying expectations and conditions of use. Each sensor was evaluated based on its operational feasibility that included cost conditions, telemetry availability, and ease of operation, and its performance accuracy.
This research is unprecedented, to the best of our knowledge, and aims at a comprehensive evaluation of sensors for factors that are not commonly recognized when assessing soil moisture sensing technology. Immense potential exists for the application and use of the findings of this research for sensor selection by diverse users is concerned.
Advisor: Suat Irmak