IDENTIFICATION AND CONTROL OF HYDROPONIC SYSTEM USING ION SENSORS
The diurnal courses of the consumption of Ca2+, K+ and NO3- fluctuated periodically and the negative consumption of ions appeared many times. This was notable during the night in three sorts of ions. Positive consumption of these ions in the daytime were not corresponded to quantum flux density during the first half of vegetative stage but during the pollinating stage in which the ion consumption became higher, these were corresponded to quantum flux density. On the other hand, the consumption of water caused by transpiration was closely related to the quantum flux density in every growth stages. The EC decreased until the first half of the developmental stage of fruit but after that stage, it increased. The pH decreased in every growth stages.
As for the daily patterns of ion consumption, these increased according to the vegetative growth and reached to the maximum values from 5 to 14 days after pollination. The consumption of water also increased with the vegetative growth and reached to the maximum value just after pollination.
These findings are reflected to the new algorithm of computer control in the nutrient solution, resulting in energy saving.