ISHS Acta Horticulturae 171: I International Symposium on Water Relations in Fruit Crops
A CAPACITANCE SOIL MOISTURE METER |
| Authors: | S. Hadi, A.T. Julian, P. Newton |
| Abstract:
A simple sensor made from two lengths of wire has been devised in order to determine changes in soil water content. The capacitance between the two wires is modified by the presence of water, and when connected to an instrument whose construction is based on the circuit diagram of Clymo and Gregory (J. app. Ecol, 1975), gives a linear increase in meter reading with decrease in soil water percentage. With our soil at intermediate water content, errors associated with changes in soil temperature from 5°C to 25°C and are of the order of 10%, for change in soil conductivity from 100 to 2000 millisiemens/cm. Errors are less with dry or wet soil. The sensor needs to be calibrated for each type of soil, but as both sensor and meter are very cheap to produce, they need not be a limiting factor determining the number of replicates that can be used in the field. The time taken per reading is only a few seconds, the number of readings determined "by hand" per hour largely depends on the time taken to walk from position to position. The meter can be modified for use with a data logger, hence a continual record of soil water content can be obtained. | |
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