科研之友
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摘要
Automated sensing and control of macronutrients in hydroponic solutions would allow more efficient management of nutrients for crop growth in closed systems. This article describes the development and evaluation of a computer-controlled nutrient management system with an array of ion-selective electrodes (ISEs) and fertilizer pumps that could effectively manage concentrations of NO3, K, and Ca ions in closed hydroponic systems. A fertilizer dosing algorithm was developed to calculate the volumes of individual nutrient stock solutions to be supplied based on the measurement of present concentrations in a mixing tank. In a five-step spiking test, the system was able to formulate five different concentrations of NO3 and Ca ions comparable to the target concentrations, showing almost 1:1 relationships between the actual and target values. However, actual K concentrations were prepared almost 40% higher than target concentrations due to low K estimates. The use of a two-point normalization method in conjunction with ISEs was effective in minimizing signal drifts resulting from in-line measurement of ion concentrations in the closed system. The automated nutrient management system was used to grow lettuce in a greenhouse with the ebb and flow method After water was automatically added to the mixing tank to maintain the level of water within 10% of the total volume of the tank, the amounts of three different salts, i.e., KNO3, KH2PO4, and Ca(NO3)(2), were variably supplied to the mixing tank based on real-time measurement of concentrations. The three ions were automatically controlled to reach target concentrations of 280, 140, and 70 mg L-1 within errors of -7.7 +/- 28.1, 20.8 +/- 28.5, and -5.6 +/- 8.2 mg L-1 for NO3, K, and Ca ions, respectively.
- 出版日期2015-10
