Abstract
To research the cyclic use of the drainage solution in a closed system of rockwool cultivation of cut roses, we examined the effects of diluting the drainage solution with water, both with and without additions of NH4-N, Fe and Mn nutrient components following the slow sand and active charcoal filtration of the drainage solution. The yields of the cut flower stems were almost the same as those in the conventional cultivation, at 35 per plant, when the drainage solution was recirculated, and whether or not we added nutrient components. The cut flower stem quality was almost the same as those in the conventional cultivation, in each drainage cycle. Under the conventional cultivation system, the total nitrogen quantity applied per 1,000 m2 cultural facilities for 1 year was 290.3 kg, and the quantity for disposal was 135.9 kg. Under the closed system, using the added nutrient components, the total nitrogen quantity was 151.8 kg, and with no added nutrients components, the total for disposal was only 110.5 kg. In addition, under the closed systems, there was no nitrogen and phosphoric acid to dispose of in each drainage cycle. PO4-P, Mn, Fe and SO4-S concentrations in the drainage solution were lowered, after the drainage solution was slowly filtered. Na and Cl concentrations in the solution rose remarkably when the filtered drainage solution was circulated. However, no symptoms of mineral excess or deficiency were observed in the rose plants. In a closed system of rock wool rose cultivation, it was shown that there was no neccessity to supplement the nutrient components, when the drainage solution was diluted by 2.5 times after slow filtration process.
