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United States Department of Agriculture

Agricultural Research Service

Title: Automated Collection of Soil-Moisture Data with a Low-Cost Microcontroller Circuit

Author
item Fisher, Daniel

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 4, 2007
Publication Date: September 14, 2007
Citation: Fisher, D.K. 2007. Automated collection of soil-moisture data with a low-cost microcontroller circuit. Applied Engineering in Agriculture. 23(4): 493-500

Interpretive Summary: Appropriate timing of irrigations is necessary for proper plant growth, improved crop yields, and efficient use of water resources. Monitoring the moisture status of the soil profile is one method used to schedule irrigations. The manual collection of moisture-sensor data can be time- and labor-intensive, however, resulting in data often being collected at irregular or infrequent intervals. Automating the data-collection process allows information to be collected at high frequency with less labor requirements. A microcontroller-based circuit was designed to continuously monitor and record moisture-sensor data. The circuit is simple to build, constructed of inexpensive electronic components, and capable of storing long-term, high-frequency measurements. Reducing the cost of automated measurement equipment will provide time, labor, and cost savings, and allow information to be collected from more locations. Irrigators can benefit by more easily and accurately monitoring soil-water resources and, thus, better scheduling irrigations. Researchers and irrigators can have access to high-density, high-frequency moisture data for use in precision irrigation applications. Equipment companies and entrepreneurs can incorporate this type of inexpensive circuitry into commercial products to provide cost-effective, automated moisture information for more efficient irrigations.

Technical Abstract: Monitoring the moisture status of the soil profile is one method used to schedule irrigations, but the manual collection of moisture-sensor data can be time- and labor-intensive and cost-prohibitive. Automating the data-collection process allows information to be collected at higher frequencies, regular intervals, and with less labor requirements. A microcontroller-based circuit was designed and constructed using inexpensive electronic components to continuously monitor and record moisture-sensor data. The circuit was designed to monitor three Watermark moisture sensors and one temperature sensor, and to record data at 2-hour intervals for an entire year. The circuit included a microcontroller, real-time clock, non-volatile memory, and an alternating-current, sensor-excitation subcircuit. A calibration routine was developed and programmed into the microcontroller to convert raw sensor signals to water-potential measurements. Over two growing seasons, 150 circuit boards were constructed and deployed in different corn, soybean, and cotton fields to provide information for scheduling irrigations. Data were downloaded periodically to a handheld computer and input to a desktop-computer spreadsheet for graphing and analysis and for irrigation scheduling. The circuit was simple to build, cost under $20 in materials, and performed reliably in field tests. This type of simple, inexpensive automated measurement equipment can provide time, labor, and cost savings, and allow information to be collected at higher frequencies and from more locations for use in irrigation scheduling and precision irrigation applications.

Last Modified: 7/30/2014
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