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Title: INTEGRATION OF HEAT CAPACITY AND ELECTRICAL CONDUCTIVITY SENSORS FOR ROOT MODULE WATER AND NUTRIENT ASSESSMENT

Author
item HEINSE, ROBERT - UTAH STATE UNIVERSITY
item LEWIS, KELLY - UTAH STATE UNIVERSITY
item JONES, SCOTT - UTAH STATE UNIVERSITY
item KLUITENBERG, GERARD - KANSAS STATE UNIVERSITY
item Austin, Richard
item Shouse, Peter
item BINGHAM, GAIL - SPACE DYNAMICS LABORATORY

Submitted to: International Conference on Environmental Systems
Publication Type: Proceedings
Publication Acceptance Date: 6/15/2006
Publication Date: 7/1/2006
Citation: Heinse, R., Lewis, K., Jones, S.B., Kluitenberg, G., Austin, R.S., Shouse, P.J., Bingham, G.E. 2006. Integration of heat capacity and electrical conductivity sensors for root module water and nutrient assessment. International Conference on Environmental Systems July 27-30, 2006 at Norfolk, VA. Paper No. 2211

Interpretive Summary: Management of water and nutrients is becoming more critical in plant production systems and we need to develop more sophisticated real-time devices to help monitor our decisions. Our objectives were to determine if dual-probe heat pulse sensors could improve accuracy of water content determinations compared to single-probe heat-pulse sensors, and to test a coupled heat-pulse and direct-current electrical conductivity sensor. We found that single-probe heat-pulse sensors were less sensitive to water content changes, but accuracy was improved by using an empirical calibration making them comparable to dual-probe sensors. Electrical conductivity as a function of water content was well correlated for water contents above 0.2 cm3 cm-3. Combining water content electrical conductivity measurements in a single sensor provides improved root zone environmental assessment and increased managerial support capabilities

Technical Abstract: Management of water content and nutrient status during space flight is a critical necessity in plant production systems. Our objectives were to determine if dual-probe heat pulse sensors could improve water content determination accuracy over single-probe heat-pulse sensors, and to test a design using coupled heat-pulse and direct-current electrical conductivity sensors, paired as a 4-electrode array. The dual-probe heat-pulse data correlated well with measured water contents based on a physically-derived one-point calibration model. Single-probe heat-pulse data were less sensitive to water content changes using a similar theoretical approach. Water content prediction improved, and was comparable to the dual-probe sensors when using an empirical relationship. Water content was predicted with a root-mean square error of 0.03 cm3 cm-3. Electrical conductivity was measured in both saturated flow-through and static unsaturated measurements. Model predictions of solution electrical conductivity as a function of water contents were well correlated for water contents above 0.2 cm3 cm-3. Combining the dual-needle heat pulse probe water content determination with electrical conductivity measurements provides improved root zone environment assessment and management capabilities