Acquiring In-Situ High-Resolution Soil Information Using Cost-Effective Technology

Abstract

Crop production and ecosystem services are greatly influenced by soil’s physical properties (i.e. soil moisture, organic carbon, particle size distribution, bulk density, etc.). This thesis develops new in-situ and laboratory technologies that can accurately measure soil physical properties rapidly and cost-effectively across the cropping fields. The first challenge is to build a soil water monitoring system that can monitor crop water use at the plot level. The study used a plastic buggy system for electromagnetic induction (EMI) surveys. The electrical conductivity data recorded from the EMI surveys were used for the depth-specific temporal analyses of soil water use by different genotypes. The system was successfully used to monitor soil water uptake by 36 genotypes of chickpeas at the plot level. The second challenge is to develop a rapid in-situ soil organic carbon (SOC) measurement technique using a VisNIR penetrometer system with high-resolution in-situ spectra. This method can measure SOC contents accurately from the surface up to the depth of 90 cm. The thesis also investigates novel laboratory techniques for measuring the particle-size distribution and bulk density. An automated hydrometer method using a ToF distance and a digital temperature sensor was introduced to measure continuous particle-size distribution. A novel technique based on shear wave velocity using piezoelectric sensors was developed for measuring bulk density and soil stiffness moduli in the laboratory. These cost-effective and robust measurement systems for measuring 3-dimensional high-resolution soil physical properties can be used in precision agriculture to optimise the resources for maximum crop yields.