Design and testing of an autonomous irrigation controller for precision water management of greenhouse crops

The automation of irrigation systems based on sensor technology has the potential to maximize the efficiency of water use. A prototype of an autonomous irrigation controller consisting of an 8-bit MCU and a 12-bit AD converter was developed and tested in tomato greenhouses. Two algorithms for water control, i.e. a variable keep-pause method and a required water calculation method, were programmed. The irrigation controller showed the ability to measure soil tensions in real-time and to properly trigger irrigation at a set value. The system performance for maintaining soil tensions based on the keep-pause method was strongly affected by sunlight, whereas the water calculation method provided a simple irrigation operation without frequent irrigation, while supplying the amount of water needed during each irrigation period.