2017 Volume 16 Issue 1 Pages 19-25
The sediment of suspended solids (SS), which is derived from the hydroponic gutter after the cultivation of water spinach (Ipomoea aquatica Forssk.) using eutrophic water from Lake Tega, was granulated as granular medium (SS medium). The characteristics of this SS medium and its applicability to vegetable cultivation were studied. The freshly granulated SS medium contained lower NO3-N, but higher exchangeable Mn than commercial soil medium. However, after aerobic fermentation under 30°C, the NO3-N content, exchangeable Mn, and water-soluble Mn in SS medium were markedly increased, with a decreased water content. The early growth of spinach mustard (Brassica rapa L. Perviridis Group) was suppressed using the fermented (30°C) medium, possibly due to the excessive Mn. The Mn content in mixed SS medium with bark compost (SS + bark) were also measured in the present study. The results show that the exchangeable and water-soluble Mn content was significantly decreased by mixing of SS medium and bark compost under 30°C fermentation. Moreover, the Mn content in both the SS medium and SS + bark medium was even decreased under 45°C fermentation treatment with a value of less than 30 mg・kg–1, regardless of the water content of the medium. Although the growth of spinach mustard on the fermented SS + bark medium was lower than that on commercial soil medium, aerobic fermentation improved the chemical properties of SS + bark medium, and SS sediment was considered to show potential for use as growing medium by mixing with bark compost.
