Improved soil water sensors aid in irrigation management

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Source: Soil Science Society of America

Agriculture, a large user of water for irrigation, is under pressure to reduce water use. Increased urban population growth has created more competition for limited water supplies. While growers have used soil moisture probes to aid in irrigation management in the past, earlier probes required maintenance or were expensive or inadequate.  New electronic sensors have been developed that require minimal maintenance and are more affordable. This study evaluated and developed calibration information for one of the newer probes. These probes can be placed at different depths in the soil and show growers how deep water has moved.  With probes such as these, growers can maintain water in the root zone better, and reduce over-irrigation.  Minimizing over-irrigation reduces water loss and leaching of nutrients and promotes greater water use efficiency.

Drs. Larry Parsons and Wije Bandaranayake of the University of Florida / IFAS Citrus Research & Education Center in Lake Alfred, FL carried out research on one of these new soil moisture sensors, the ECH2O EC-5 manufactured by Decagon Devices. Their study evaluated the sensors in terms of volumetric soil water content estimation, probe-to-probe signal variability, response to fertilizer-induced salinity, soil volume sampled by the probes, sensitivity to pockets of air or dry soil, response to compaction (bulk density changes), and response to changes in soil temperature.

The results were published in the July-August 2009 issue of the Soil Science Society of America Journal and were presented at the annual meetings of the Soil Science Society of America held in November 2007 in New Orleans, LA. The work was funded in part by the Southwest Florida Water Management District.

Results showed that the new sensor has several advantages. The ECH2O EC-5  was not sensitive to salinity or temperature fluctuations.  Although the soil volume sampled by the probe was small (about 15 cm3), the probe responded well to changes in soil water content in the field.  The change in probe response was negligible when soil pores (diameter 0.95 cm) were created near the probe surface.  Probes were sensitive to changes in bulk density. Signal output increased when soil was compacted.  Probe-to-probe output signal variation and response to differences in bulk density can affect the estimation of field water content unless necessary correction factors are utilized.

Soil probes can be useful for monitoring soil water movement, estimating soil water content, and scheduling irrigation.  They can be used on a variety of soils and with numerous crops.  With a datalogger, soil water content can be monitored continuously over time and changing trends can be noted.  Soil water data from these probes can be transmitted by radio to computers at other locations.  Research using these and other sensors is continuing at the University of Florida to investigate ways to keep irrigation water in the main root zone, reduce deep percolation water losses, and minimize irrigation water use.  With sensors such as these, improved irrigation efficiency is possible.

Trade names are sometimes mentioned in papers published in the Soil Science Society of America Journal. No endorsement of the product by the publisher is intended, nor is any criticism implied of similar product not mentioned. Opinions and conclusions expressed by authors are their own and are not considered as those of the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, its staff, its members, or its advertisers. Advertisements in the publications and/or websites do not constitute an endorsement of the product.

The full article is available for no charge for 30 days following the date of this summary. View the abstract at http://soil.scijournals.org/cgi/content/abstract/73/4/1378.

Soil Science Society of America Journal, http://soil.scijournals.org, is a peer-reviewed international journal published six times a year by the Soil Science Society of America. Its contents focus on research relating to physics; chemistry; biology and biochemistry; fertility and plant nutrition; genesis, morphology, and classification; water management and conservation; forest, range, and wildland soils; nutrient management and soil and plant analysis; mineralogy; and wetland soils.

The Soil Science Society of America (SSSA) is a progressive, international scientific society that fosters the transfer of knowledge and practices to sustain global soils. Based in Madison, WI, and founded in 1936, SSSA is the professional home for 6,000+ members dedicated to advancing the field of soil science. It provides information about soils in relation to crop production, environmental quality, ecosystem sustainability, bioremediation, waste management, recycling, and wise land use.

SSSA supports its members by providing quality research-based publications, educational programs, certifications, and science policy initiatives via a Washington, DC, office. For more information, visit www.soils.org.

SSSA is the founding sponsor of an approximately 5,000-square foot exhibition, Dig It! The Secrets of Soil, which opened July 19, 2008 at the Smithsonian's National Museum of Natural History in Washington, DC.

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