Development of automatic irrigation and soil moisture monitoring system based on solar energy in citrus orchard

In order to irrigate orange garden with the goal of automation, save water and power, solar energy was used to supply the power for the automatic irrigation and soil moisture monitoring system. Soil moisture sensor was used to real-time detect water content in soil. To monitor the soil moisture of the orange garden, controller area network (CAN) bus and global system for mobile communications (GSM) network were used to transmit the results. Solar cell was used to charge Li-ion battery. Two Li-ion batterys were used to separate the charging and discharging process, which enhanced the stability of power supply of the system. Soil moisture sensor worked one time per 12 hours. The determined value was lower than the setting value, the radiotube would be open automatically, in contrast, the radiotube would be closed. Data of water content in soil of 666.7 m2 area was transferred to the main node through CAN bus, which transmitted the data to terminal computer by short messages. Below 10% and above 20% of the water content in soil was taken as the beginning and end of irrigation, respectively. With the sensor placed out of the dropper pipe about 50 mm, the irrigation time was about 6.7 hours. The experiments showed that the system ran stably, and could implement automatic irrigation and monitoring soil water content of the orange garden, which was significant for realizing water and energy saving irrigation.