Automatic gamma-ray equipment for multiple soil physical properties measurements

Determination of soil physical parameters is sometimes very laborious and time consuming. For instance, the soil water retention curve takes several weeks. Particle density by picnometer and granulometry (texture) by pipette method are laborious methods. Other parameters, such as bulk density and total porosity, are determined by gravimetric methods and depends on oven drying the samples for 24 hours. In order to help in the soil physical parameters determination we have developed automatic equipment based on the attenuation of a gamma-ray beam by soil samples. Two types of samples are analyzed: solid (undisturbed) and dispersed soil particles in water, allowing the measurement and estimation of the following parameters: Particle size distribution (measured); Retention curve (estimated by Arya and Paris (1981) method); Particle density (estimated from measured mass attenuation coefficient of the soil sample); Bulk density (measured); Total porosity (estimated); Water content (measured). Here we focus on the explanation of gamma-ray attenuation method to measure and estimate the soil physical parameters mentioned above. Each method will be presented in detail together with calibrations and practical applications