Advances in the Determination of Soil Moisture Content

This chapter discusses some advanced methods that are used to extract information from electrical signals, and how this could be used to predict soil moisture content. A brief explanation of what is meant by signal and various signal processing techniques, either by summation of elemental signals (synthesis) or by decomposition into elemental signals (analysis), is discussed. To demonstrate the synthesis methods, pulse and sinusoid signals are applied; whereas, for decomposition analysis, both time domain and frequency domain analyses are discussed. In frequency domain analysis of signals the use of the Time Domain Reflectometry (TDR) and Fourier spectral analysis to predict soil moisture content and salt concentration is demonstrated. Unlike Fourier decomposition, which partitions signals based on harmonic frequencies by using parametric sines and cosines, eigen-decomposition analysis, separates signal components by differences in their power. These methods are applied in several case studies for the determination of soil moisture content, soil density, clay content, salt concentration, and organic fluid content.