a measurement new method of coefficient in no saturation guiding hydrolic by four electrood hygrometer

considering soil properties, moisture is of central significance, affecting its physical characteristics and behavior. that is why, determining soil water volume and the way it moves through soil is of importance. the most basic parameter in water movement is hydraulic conductivity in saturated and unsaturated conditions.the present study, incorporating campbell method of soil characteristic curve, aims at developing a method for soil moisture measurement, suggesting a new method to measure unsaturated soil hydraulic conductivity.in this research, soil moisture was obtained by using four electrode method through installation of moisturemeters in soil layers in test cylinder, and soil resistance is measured by measuring voltage between electrodes of moisturemeters, making use of richard’s partial differential eqution and finite difference method. the hydraulic conductivity of the soil under experiment (silty clay of mazandaran) was determined with a variety of initial water contents. test results are in expected range and fitted equation k=10 -10 . e  49.755 θ shows a very good agreement with them.in spite of the fact that four electrode method may not be as accurate as some other methods, its simplicity and the lower expenses in addition to the possibility of installation in site to control soil water movement makes it advantageous among others.