soil moisture sensor

i want to design soil moisture sensor .....suggest any circuit ???help me out wat kind of probe i must use???

Welcome, sibghat!
Here's one that you may be able to use:

Soil Moisture Tester

Hope this helps!
Der Strom

There is a probe type the is buried in the ground permanently. It uses stainless steel electrodes inside a plaster/gypsum block.

Hi sibghat,

here are construction details of an earth moisture sensor. The electrodes are embedded in gypsum which will have the same moisture level as the surrounding soil.

All dimensions are in Millimeters.

I strongly recommend to use stainless steel rods for sensor wires for least or no corrosion. Otherwise you must recon on replacing the sensor every six to twelve months.

(Wires can be soft soldered to stainless steel applying enough heat and using flux. Before soldering use sulfuric acid to remove the protection layer of the steel, rinsing it thoroughly with water after applying the acid.)

I have a controller circuit under development allowing any moisture level from 5% to soaking wet, depending on the plants to be watered.

Boncuk