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Validation testing of an ion-specific sensing and control system for precision hydroponic macronutrient management

D. Jung,H. Kim,Woo-Jae Cho,S. Park,Seung-Hwan Yang

Published 2019 in Computers and Electronics in Agriculture

ABSTRACT

Abstract Ion-specific nutrient management systems would replace conventional electrical conductivity-based management systems for more efficient maintenance of the concentration of each ion in nutrient solutions for closed hydroponic systems. This study reports on the validation testing of a previously developed ion-specific sensing and control system. Specific objectives were to (1) evaluate the ability of the system to maintain the target concentrations of five macronutrients, i.e., NO3−, PO43−, K+, Ca2+, and Mg2+ ions, required for crop growth in closed hydroponic systems based on both real-time measurement of NO3−, K+, and Ca2+ and the use of a concentration ratio method to replenish Mg2+ and PO43−, and (2) investigate the applicability of a cobalt rod-based electrode for hydroponic phosphate sensing. In a lettuce cultivation test conducted with the ebb-and-flow method over 21 days, most of the macronutrient concentrations were successfully maintained at the target levels with RMSE values of 25.2 ± 9.4, 19.1 ± 8.1, and 11.5 ± 6.1 mg∙L−1 for NO3−, K+, and Ca2+, respectively. In the case of Mg2+ and PO43− ions replenished in a proportional ratio to the supply of Ca2+ and NO3− ions, respectively, the Mg2+ concentrations were maintained between 18 and 25 mg∙L−1 at an almost constant level, whereas the PO43− concentrations increased steadily over time with no clear evidence of plant uptake, implying that the use of a concentration ratio method would not be effective in controlling the concentrations of PO43− in hydroponic solutions. As a phosphate sensor, the cobalt electrodes yielded an RMSE result of 10.9 ± 7.1% from a comparison of the electrode method and standard analysis when tested in hydroponic lettuce samples taken once a day during the period of lettuce growing, thereby offering the potential for use in hydroponic phosphate sensing.

PUBLICATION RECORD

  • Publication year

    2019

  • Venue

    Computers and Electronics in Agriculture

  • Publication date

    2019-01-01

  • Fields of study

    Chemistry, Computer Science, Environmental Science

  • Identifiers
    DOI 10.1016/J.COMPAG.2018.12.025
  • External record

    Open on Semantic Scholar

  • Source metadata

    Semantic Scholar

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