Here is a simple and compact digital soil moisture tester to check whether the soil is dry or wet. It can also be used to check the dryness or wetness of cotton, woolen and woven fabrics.
For indication, the tester uses a number of LEDs driven by ubiquitous display driver IC LM3915. The display panel shows the relative magnitude of conductance (reciprocal of resistance) between the two test probes when these are inserted in the soil. The tester measures the dryness or wetness through soil resistance readings (0 to about 5 kilo-ohms) and indicates in dot mode by sequential lighting of LED1 through LED8.