Response of Capacitance Probes to Soil Solution Nitrate Concentration

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2009-06-01
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Kaleita, Amy
Birrell, Stuart
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Kaleita, Amy
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Birrell, Stuart
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Agricultural and Biosystems Engineering

Since 1905, the Department of Agricultural Engineering, now the Department of Agricultural and Biosystems Engineering (ABE), has been a leader in providing engineering solutions to agricultural problems in the United States and the world. The department’s original mission was to mechanize agriculture. That mission has evolved to encompass a global view of the entire food production system–the wise management of natural resources in the production, processing, storage, handling, and use of food fiber and other biological products.

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In 1905 Agricultural Engineering was recognized as a subdivision of the Department of Agronomy, and in 1907 it was recognized as a unique department. It was renamed the Department of Agricultural and Biosystems Engineering in 1990. The department merged with the Department of Industrial Education and Technology in 2004.

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1905–present

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  • Department of Agricultural Engineering (1907–1990)

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Agricultural and Biosystems Engineering
Abstract

Dielectric properties of soil are highly correlated with volumetric water content (VWC) of the medium, but at a relatively low frequency soil salinity has an important effect on permittivity measurements. A laboratory experiment was conducted to understand the potential of monitoring nitrate and chloride ions in soil solutions using capacitance-type soil probes EC-5 and EC-10 operating at frequencies of 70 and 5 MHz, respectively. Dielectric response of soil samples wetted with nitrate and chloride solutions of different concentration were compared at each frequency within the volumetric water content ranging from 0.1 to 0.3 m3/m3. Linear regression models were fitted through data to correlate the actual VWC, concentration of solutions, soil temperature and sensor output. At 70 MHz frequency the sensor response was primarily explained by moisture content for both solutions. Dielectric response of the EC-10 probe to change in ionic concentration was different for each wetting solution. Change in chlorine concentration demonstrated no evidence of having effect on the sensor response, while nitrate solution illustrated that the EC-10 probe is sensitive to the change in nitrate-N concentration within the water content and salinity range tested (from 0.05 to 0.51 dS/m). None of the fitted models demonstrated the statistically significant effect of temperature on dielectric measurements due to the little variation of the temperature (+/- 1.5°C) during the experiment.

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This is an ASABE Meeting Presentation, Paper No. 097211.

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Thu Jan 01 00:00:00 UTC 2009