Estimating EC and ionic EC contribution percentage of nutrient solution based on ionic activity
Keywords:
hydroponics, nutrient solution, ionic activity, soilless culture, Debye-Hückel limiting equation, ionic EC contribution percentage, nutrient formula, solution dynamic controlAbstract
The dynamic monitoring technology of inorganic ions using ion selective electrodes has some problems such as low precision, vulnerability to other ions, short service life, and high price. Due to the difficulty of dynamic control based on ionic concentration of nutrient solution, EC and pH values of nutrient solution are often used as feedback control indexes in hydroponic system. In this study, estimation algorisms of EC and ionic EC contribution percentage based on ionic activity were proposed to understand the quantitative relationship between ionic concentration and EC. With a view to predicting the EC accurately by mean ionic activities of specific salts in nutrient solution based on a specific formula, ionic concentration could also be calculated by the actual measurement of EC combined with ionic EC contribution percentage. With Japanese horticultural experimental nutrient formula and Yamasaki tomato nutrient formula, significant linear correlations between estimated EC and measured EC were found with determination coefficients over 0.99. Ionic EC contribution percentage was not affected by different relative concentrations of nutrient solutions. However, ionic EC contribution percentage changed significantly when adding specific salts with different concentrations, and different changes were found in each anions and cations of specific salt added. When the same K+ concentration was added in different forms of KNO3, K2SO4, KCl, and KH2PO4, the changes of ionic EC contribution percentage of K+ were similar, but those of other anions in potassium salts varied greatly. The relative errors of estimated EC of nutrient solutions based on ionic activities were only 1.3% in horticultural experimental nutrient solution and 1.8% in Yamasaki tomato nutrient solution with different relative concentrations compared to measured EC. The relative errors of estimated EC of nutrient solutions with specific salt added were only 0.1%-0.5% compared to measured EC in two nutrient solution. Therefore, the dynamic feedback control of ionic concentration of nutrient solution could be realized by using EC measurement combined with ionic EC contribution percentage to improve the ionic quantitative control in nutrient solution. The EC control of nutrient solution in automatic irrigation system might be upgraded to ionic concentration control by using algorisms above of ionic EC contribution percentage and EC estimation to meet dynamic demands of hydroponic crops for ionic concentration in different growth stages. Keywords: hydroponics, nutrient solution, ionic activity, soilless culture, Debye-Hückel limiting equation, ionic EC contribution percentage, nutrient formula, solution dynamic control DOI: 10.25165/j.ijabe.20191202.4399 Citation: Song J X, Xu L, He D X, Tuskagoshi S, Kozai T, Shinohara Y. Estimating EC and ionic EC contribution percentage of nutrient solution based on ionic activity. Int J Agric & Biol Eng, 2019; 12(2): 42–48.References
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[23] Zhang Y, Wang Z Y, Wang P, Wang X X. Application of regression analysis in determination of nutrient solution concentration of foliage plant. Journal of Anhui Agricultural Science, 2009; 37(6): 2478–2479.
[24] Xu T W, Yang W H, He B L, Liu Z M, Li S Q, Li X D. Determination of the concentration of ions in a binary system by conductivity method. Journal of Analytical Science, 2000; 16(1): 45–48.
[25] Son J E, Takakura T. A study on automatic control of nutrient solutions in hydroponics. Journal of Agricultural Meteorology, 1987; 43(2): 147–151.
[26] Liu H B, Du Z, Wu H X Li Z B, Li P, Li J. Study on the effect of different salts and their concentration on conductivity in aqueous solution. Xi’an Shanxi: Sediment Committee of China Water Conservancy Society, 2010: 632–635.
[27] Pazuki G R, Rohani A A. A new model for the activity coefficients of individual ions in aqueous electrolyte solutions. Fluid Phase Equilibria, 2006; 242(1): 65–71.
[2] Ni J H, Mao H P, Ma W Z. Research progress of nutrient solution management strategy in greenhouse. Vegetables, 2011; (6): 45–47.
[3] Qiu X F, Xue M S, Sun D M, Zhang J L. The online measurement and estimation of the nutritive medium ingredient. Journal of China University of Science and Technology, 2000; 30(3): 351–355.
[4] Li M Y, Fang T. Modeling for mean ion activity coefficient of strong electrolyte system with new boundary conditions and ion-size parameters. Chinese Journal of Chemical Engineering, 2015; 23(7): 1169–1177.
[5] Soh J W, Lee Y B. Estimated EC by the total amount of equivalent ion and ion balance model. Korean Journal of Horticultural Science and Technology, 2012; 30(6): 694–699.
[6] Son J E, and Okuya T. Prediction of electrical conductivity of nutrient solution in hydroponics. Journal of Agro Meteorology, 1991; 47(3): 159–163.
[7] Ashassi-sorkhabi H, Kazempour A. Activity coefficient modeling of ionic liquids in water based on ion selective electrode potential measurements. Journal of Solution Chemistry, 2016; 45(6): 831–839. doi: 10.1007/s10953-016-0476-8.
[8] Liu C L, Xu L J, Xian X H, Xian X F. Study on the relationship between concentration of salt solution and its conductivity. Environmental Monitoring in China, 1999; 15(4): 23–64.
[9] Chen L M, Cheng M X, Xiao X F, Huang Z H. Measurement of the relationship between conductivity of salt solution and concentration and temperature. Research and Exploration in Laboratory, 2010; 29(5): 159–163.
[10] Son J E. Experimental model and neural network based electrical conductivity estimation in soilless culture system. Acta Horticulturae, 1996; 440: 344–347.
[11] Zhu J F, Liu F, Liu S L, Jie X L, Hua D L, Lei G H. Effect of nutrient solution pH value on absorption and accumulation of mineral nutrients during tobacco seedling stage. Acta Agriculturae Boreali-Sinica, 2012; 27(4): 186–190.
[12] Ministry of Ecology and Environment of the People’s Republic of China. HJT 346-2007. Water quality-Determination of nitrate nitrogen-Distillation neutralization titration. Beijing: China Environmental Science Press, 2007.
[13] Ministry of Ecology and Environment of the People’s Republic of China. HJ 537-2009. Water quality-Determination of ammonia nitrogen-Ultraviolet spectrophotometry. Beijing: China Environmental Science Press, 2009.
[14] Ministry of Ecology and Environment of the People’s Republic of China. HJ 593-2010. Water quality-Determination of phosphorus-phosphomolybdenum blue spectrophotometric method. Beijing: China Environmental Science Press, 2010.
[15] Ministry of Ecology and Environment of the People’s Republic of China. HJ 342-2007. Water quality-Determination of sulfate-Barium chromate spectrophotometry. Beijing: China Environmental Science Press, 2007.
[16] Ministry of Ecology and Environment of the People’s Republic of China. GB 11896-89. Water quality-Determination of chloride- Silver nitrate titration method. Beijing: China Environmental Science Press, 1989.
[17] Ministry of Ecology and Environment of the People’s Republic of China. GB 11904-89. Water quality-Determination of potassium and sodium- Flame atomic absorption spectrophotometry. Beijing: China Environmental Science Press, 1989.
[18] Ministry of Ecology and Environment of the People’s Republic of China. GB 11905-89. Water quality-Determination of calcium and magnesium- Flame atomic absorption spectrophotometry. Beijing: China Environmental Science Press, 1989.
[19] Ministry of Ecology and Environment of the People’s Republic of China. GB 11911-89. Water quality-Determination of iron and manganese- Flame atomic absorption spectrophotometry. Beijing: China Environmental Science Press, 1989.
[20] Lide D R. CRC Handbook of Chemistry and Physics (84th). American: CRC Press, 2004. pp.926-928.
[21] Lewis G N, Randall M. The activity coefficient of strong electrolytes. Journal of the American Chemical Society, 1921; (5): 1112-1154.
[22] Debye P, Hückel E. On the theory of electrolytes. Ⅱ Limiting law for electric conductivity. Physikalische Zeitschrift, 1923; 24(1): 305-325.
[23] Zhang Y, Wang Z Y, Wang P, Wang X X. Application of regression analysis in determination of nutrient solution concentration of foliage plant. Journal of Anhui Agricultural Science, 2009; 37(6): 2478–2479.
[24] Xu T W, Yang W H, He B L, Liu Z M, Li S Q, Li X D. Determination of the concentration of ions in a binary system by conductivity method. Journal of Analytical Science, 2000; 16(1): 45–48.
[25] Son J E, Takakura T. A study on automatic control of nutrient solutions in hydroponics. Journal of Agricultural Meteorology, 1987; 43(2): 147–151.
[26] Liu H B, Du Z, Wu H X Li Z B, Li P, Li J. Study on the effect of different salts and their concentration on conductivity in aqueous solution. Xi’an Shanxi: Sediment Committee of China Water Conservancy Society, 2010: 632–635.
[27] Pazuki G R, Rohani A A. A new model for the activity coefficients of individual ions in aqueous electrolyte solutions. Fluid Phase Equilibria, 2006; 242(1): 65–71.
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2019-04-06
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Song, J., Xu, L., He, D., Tuskagoshi, S., Kozai, T., & Shinohara, Y. (2019). Estimating EC and ionic EC contribution percentage of nutrient solution based on ionic activity. International Journal of Agricultural and Biological Engineering, 12(2), 42–48. Retrieved from https://ijabe.migration.pkpps03.publicknowledgeproject.org/index.php/ijabe/article/view/4399
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Animal, Plant and Facility Systems
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