NOTE ELECTRO-OPT ICAL MEASUREMENT OF

Shrinkage is a very important physical property of soils owing to its influence on water balance and related consequences both on soil conservation and agronomic management. As a particular agricultural problem, shrinkage becomes important in soils with a high content of expanding types of clays, where large and deep cracks influence the root systems and therefore crop yields. Several new methods have been devised in recent years to investigate soil shrinkage (Koepf, 1960; Franzmeier & Ross, 1968; Groenevelt, 1974). The present study was undertaken to accomplish a less time consuming measurement of shrinkage by means of electro optical equipment (Leitz Classimat). The apparatus is similar to a Quantimet-B previously used by Jongerius (1972) for soil porosity investigation; it consists of an epidiascope, where the image of a shrunken sample is projected upon the photosensitive layer of a television camera, an electronic signal processing unit which analyses the video signals, and a monitor where the analysed image is also visible. The measured ata can be digitally displayed and directly fed to an electronic omputer (Olivetti P602). A simplified diagram is presented in Fig. 1. Following the shrinkage development was considered the best way to estimate the performance of the instrument and clay with a high content of montmorillonite was selected as the most suitable sample in order to enhance this process. The investigations were carried out using clay samples from the Uri Bentonite Optical-,,,,-- Television macroscopic image ca mera