Low-cost and low-power dissipation system to monitor soil water status in real time for areal irrigation management

Abstract：It is a very important and fundamental work to monitor soil water status in real time for irrigation management in modern irrigation district. This paper presented a system with low cost and low power dissipation to monitor soil water status for areal irrigation management. The instrument of soil water monitoring contains a microcontroller-based system and is powered by 1# dry cell. All of the measurement data would be sent to web server through GPRS (general packet radio services) chipset assembled in it, for analysis and use in irrigation management based on each point of distributed framework. There were 4 sets of soil water content and temperature sensors and 1 set of water potential sensor designed, which could be installed at different depth in the crop root zone to meet the demand of irrigation management. However, it could be configured with less or more sensors in the system according to the channel values of the data acquisition unit, if there was a demand in the field investigation. This process had an advantage to assess the soil moisture more accurately. The microcontroller-based system and designed circuit had the responsibility to collect/log/transfer/control the data of soil water content, temperature and water potential once every 1 h. It was a very low-power dissipation system because the center processor supported energy to each unit when it needed. The interval of data collecting could be scheduled from 30 min to 24 h if necessary. All of the daily data would be transferred to the web server and the user's E-mailbox to check out or analyze. Users could receive the alarm information if the monitoring system had errors or was out of gear. They could configure the data logger near the monitoring system in wireless network, or through the internet server using GPRS technology. The designed system was installed in the whole crop growth season in 2014 in Jiefangzha Irrigation Area, Hetao Irrigation District, Inner Mongolia. The 10 sets of real-time soil water monitoring systems were set up in the fields of main crops (sunflower, maize, wheat and vegetable) with a good spatial arrangement, respectively. After one-year operation, the system made a good performance in soil water status data collecting/logging/transformation. The result analyses showed that they could reflect the soil water content change directly and support the irrigation decision-making in areal scale. At the same time, the soil temperature and water potential data had very good behavior as well. The soil water monitoring instrument had a small enough size to set up in field, avoiding the impact to field farming and unnecessary damage. The power supply was from 2 pieces of 1# dry cell or Li-ion battery, which also had a very small volume. These features could offer the guarantee to apply them in rural area and have a long enough execution time to finish the task. Meanwhile, it could conclude the characteristics of this system and next steps of the research and development in relative research field. For the system itself, the rapid assembling and the watertight performance are the key improvement in the near future. Moreover, how to determine the reasonable monitoring value and lay out the scheme of the system combined with the remote sensing data, is the research interest and hot issue for crop water requirement forecasting.