Agricultural Irrigation Water Management Using Soil Moisture Sensors in Row Crops

Stacia L. Davis, Louisiana State University, Agricultural Center Red River Research Station, 262 Research Station Drive, Bossier City, LA, 71112:

Soil moisture sensor systems can be effective tools in agricultural irrigation water management plans by helping the producer to select irrigation initiation, alleviating stress within the growing season, and determining the termination of the irrigation season. Utilizing sensor systems require adequate knowledge of functionality and limitations. The objective of this study was to evaluate strategies for selection, installation, management, and utilization of various sensor systems.

In northern Louisiana, row crop on-farm irrigation demonstrations and research station plot studies were conducted in effort to explore multiple sensor systems. Research plot studies had the following treatments: A) Watermark (Irrometer Company, Riverside, CA) system with four sensors, B) GS1 (Decagon Devices, Inc., Pullman, WA) system with five sensors, and C) calendar-based treatment. The Watermark is a gravimetric sensor that estimates soil matric potential whereas the GS1 is a volumetric sensor that measures the volume of water per volume of soil as a fraction. The calendar-based treatment was designed to be one irrigation event every 7-10 days with the selection based on water availability and rainfall in effort to prevent water logging. The on-farm irrigation demonstrations had an irrigation technology treatment that included the Aquaspy (Aquaspy, Inc., San Diego, CA), surge valves, and computerized hole selection. The Aquaspy was used to estimate soil moisture at 4 inch intervals up to 48 inches deep. This tube-style sensor takes relative measurements of soil moisture based on a scale from 0% to 100% using a radio frequency. The technology treatment was compared with a similar field that was completely controlled by the producer.

Results showed that the GS1 sensors provided more information to the user than the Watermark sensors when used in lighter textured soils. The Watermark sensors provided data that was much less intuitive when interpreting soil moisture changes within the physical system. The opposite was true in the heavier textured soils where the GS1sensors were less accurate or reliable resulting in little or no usable data over the growing season. In this situation, the Watermark sensors had better performance with increased reliability when used for irrigation scheduling. The on-farm irrigation demonstrations were useful in determining the limitations for implementing soil moisture technologies in real production scenarios. Overall, the producers were willing to use the technology when it is available, but have not yet accepted the economic value.

Keywords: Crops, Irrigation, Sensor, Soil moisture

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