The Economical Management of Recirculation Solution and Development of Automatic Controlling Program for Hydroponics

in HortScience

Experiments were carried out to determine nutrient management system for butterhead lettuce `Omega' and leaf lettuce `Grand Rapids' in nutrient film technique (NFT), and to develop a rapid and reliable program for recirculation solution. The effects of controlling solutions with UOSL (Leaf Lettuce solution of the Univ. of Seoul, Korea; NO3 -N 10.55, NH4 -N 1.02, P 2.0, K 6.7, Ca 3.5, Mg 2.0, SO4 -S 2.0 me·L-1; Fe 2.0, Cu 0.1, B 0.5, Mn 0.3, Zn 0.3, Mo 0.05 ppm) were studied by greenhouse with managing by distilled water (DW), managing pH and EC (CM), managing by nutrient solution analysis (MN), managing by nutrient solution with leaf analysis (ML). The CO2 assimilation, transpiration rate, relative chlorophyll contents, leaf color, fresh weight and dry weight were highest in MN control in the butterhead `Omega' and in MN and ML control in the leaf lettuces `Grand Rapids'. The highest relative growth rate (RGR) was in MN ML in the butterhead `Omega' but those wasn't in the leaf lettuce `Grand Rapids'. Calculation program of adjustable solution was based on the main works by Visual Basic 5.0. The developed program could select an automatic and passive process considering the type of fertilizers, run-off rate, nutrient concentration, and water volume, for calculation. All of them were done successfully by the fast and precise calculation program.

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