QUARTZ PORPHYRY TREATMENT ALTERS IRRIGATION WATER CHEMISTRY, AFFECTING HYDROPONIC VEGETABLE PRODUCTION

This study focused on using quartz porphyry (QP) as a water treatment to improve hydroponic production of komatsuna (Brassica rapa L. nothovar; Japanese mustard spinach). We compared the chemistries of the control and QP-treated nutrient solutions and found that magnesium (Mg2+) and calcium (Ca2+) concentrations increased linearly up to day 21 following sowing in both conditions, then declined slightly. The QP treatment reduced sodium (Na+) and chloride (Cl-) concentrations for the whole cultivation period. In both the control and QP-treated solutions, nitrate (NO-3) and sulfate (SO2-4) showed the same trend to a daily increase. In spite of these similarities, however, komatsuna production was better with the QP-treated nutrient solution compared to control. Treatment with QP during cultivation in August-September reduced the harmful effects of Na+, chloride (Cl-), nitrite (NO-2), and SO2-4 by reducing concentrations of these ions, possibly leading to decreased salinity and toxicity effects in the plants. Mineral concentrations during October-November differed from those of August/September, resulting in variation among the different growth parameters for komatsuna.