Comparison of sensor-based and weather-based irrigation scheduling

Authors: Sui, Ruixiu; Vories, Earl

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2020
Publication Date: 6/10/2020
Citation: Sui, R., Vories, E.D. 2020. Comparison of sensor-based and weather-based irrigation scheduling. Applied Engineering in Agriculture. 36(3): 375-386. https://doi.org/10.13031/aea.13678.
DOI: https://doi.org/10.13031/aea.13678

Interpretive Summary: Ongoing depletion and stagnant recharging of the Mississippi River Valley Alluvial Aquifer jeopardize the long-term availability of the aquifer and place irrigated agriculture in the Mid-South on an unsustainable path. It is necessary to seek improved irrigation technologies to increase water use efficiency for sustainable use of water resources. USDA ARS Scientists at the Sustainable Water Management Research Unit in Stoneville, MS, and the Cropping Systems and Water Quality Research Unit in Portageville, MO, conducted research on the comparison of sensor-based irrigation scheduling method (SBISM) and the Arkansas Irrigation Scheduler (AIS) in the Mississippi Delta. Two years of tests in soybean and cotton crops showed the number and time of irrigation events scheduled by the SBISM differed from those predicted by the AIS, which could be caused by the lack of precision in the AIS crop coefficient functions and the difficulty in interpreting the sensor values due to the highly variable soils. Both the sensor-based irrigation scheduling method and the AIS could be used as tools for irrigation management in the Mid-South region, but extra attention to the effective portion of rainfall or irrigation would be needed. Results of this study provide useful information for improving the AIS prediction accuracy in irrigation management in the Mid-South.

Technical Abstract: Sensor-based irrigation scheduling methods (SBISM) use sensors to measure soil moisture and schedule irrigation events based on the soil-water status. With rapid development of soil moisture sensors, more producers have become interested in SBISM. Arkansas Irrigation Scheduler (AIS) is a weather-based irrigation scheduling tool that has been adopted in the Mid-South for many years. Field studies were conducted for two years in Mississippi and a year in Missouri to compare SBISM with the AIS. Soil moisture sensors were installed in multiple locations of a soybean field (Mississippi) and a cotton field (Missouri). Soil water contents of the field were measured across the growing season. The AIS was installed in a computer and a nearby weather station was employed to obtain all data required. Number and time of the irrigation events triggered by the SBISM were compared with those scheduled by the AIS. Results showed the number and time of irrigation events scheduled using the SBISM were often different from those predicted by the AIS, especially during the 2018 growing season. The highly variable soils at the Missouri site made it difficult to interpret the sensor values. While all of the sites were within the Tiptonville silt loam mapping unit, many of the measurements appeared to come from sandier soils. The AIS assumed more water entered the soil than the sensors indicated from both irrigations and rainfalls less than 25 mm. Furthermore, the difference varied among sites, especially for rainfall large enough to cause runoff. The recommendations based on the Watermark sensors agreed fairly well with the AIS in July after the data from the sandiest site was omitted; however, the later irrigations called for by the AIS were not indicated by the sensors. Both the sensor-based irrigation scheduling method and the AIS could be used as tools for irrigation management in the Mid-South region, but extra attention to the effective portion of rainfall or irrigation would be needed in some years.