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Field evaluation of dual frequency multi-sensor capacitance probes for water and nutrient management in drip irrigation.

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2007 ASAE Annual Meeting  072200.(doi:10.13031/2013.22982)
Authors:   Ian R McCann, James L Starr
Keywords:   Nitrogen, salinity, irrigation management, soil water content, volumetric ion content

Capacitance sensors are now commercially available that operate at two frequencies. At one frequency the sensor responds to soil water content while at the other frequency it responds to solute concentration. We used these sensors, located at 10, 20, 30, 50 and 70 cm depth in a multi-sensor probe configuration, in 2005 and 2006 in mulched drip irrigation of seedless watermelon in Delaware. The probes were located in the center and halfway to one edge of the bed in two replications of two fertigation treatments, and were logged at 30 minute intervals. A total of 168 kg N/mulched ha (150 lb/mulched ac) was applied to each treatment, with one third of it applied preplant. The remaining N (112 kg N/mulched ha (100 lb/mulched ac) was split into either two or four equal fertigations. The objective was to evaluate the response of the sensors to the irrigations (equal for both treatments) and to the N content of the soil as affected by soil water movement and fertigation. Preliminary results indicate that the sensors did respond to the fertigations, and were able to provide insight into the relative changes in both water content and solute concentration. As such, they may be a promising research and management tool in appropriate light textured soils.

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