Water shortage as demand for more stable water sources increases, has become an important issue given the fact the agriculture sector is the highest consumer of water resources in any country. More efficient ways of water consumption, therefore, must be devised in order not to hamper the chain of food production in the country. Irrigation planning and choice of the proper method or system for irrigating farms might be an important management solution. In Iran , use of pressurized irrigation systems such as center pivot and linear because of small farm lands and topography may not be possible. For this reason, solid set irrigation system with removable sprinkler has become popular and fit with farmers’ farming conditions. To improve water use efficiency in solid set systems more than ever, a variable rate sprinkler working based on site specific soil moisture measurements by sensor was designed and evaluated under laboratory set up. Information related to land slope, soil texture, soil moisture content at field capacity (FC), plant permanent wilting point (PWP) and root development depth (Z) were given to a controller. The soil moisture sensor was from the type of FDR which transmitted data via wireless system. The controller and the sensor were designed based on AVR. Based on the data collected, flow and duration of irrigation would be determined automatically. Two variable rate sprinklers were designed and fabricated, one from brass which was tested with 3 levels of flow and second one equipped with an electric valve with 7 flow levels. Laboratory evaluation of the sprinkler with electrical valve showed that nozzle combination would result in a change in spray pattern from triangular to trapezoid pattern. This resulted in better performance of the sprinkler indices and meanwhile an increase in laterals distances which would lower initial investments in sprinkler irrigation systems. Use of different combinations of nozzles would improve uniformity of distribution. Maximum distribution coefficient of 89.3% for triangular spray pattern was obtained with lateral and sprinkler spacing (Sm × Sl) for 8+6+4 nozzle combination at 4 Bar pressure. However, considering economic aspect of system installation, the best performance for this sprinkler with same combination was obtained at 4.5 Bar with 40×30 meter spacing. The performance indices for 8+6+4 nozzle combination distribution coefficient, distribution uniformity and application efficiency were 80.1%, 80.14% and 69.32%, respectively. Distribution coefficient for nozzle combinations of 8+6, 8+4 and 6+4 at 4.5 Bar pressure and overlapping of 26×70%, 26×70% and 6×55%were 83.5%, 86.4% and 66.5%, respectively. The brass made sprinkler did not have nozzle combination but its
