Closed and recycling syslematization on hydroponics

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 12660227
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 農業機械学
• Research Institution: Utsunomiya University
• Principal Investigator: SHIGA Tohru Utsunomiya University, Fac. of Agriculture, Professor, 農学部, 教授 (30089932)
• Co-Investigator(Kenkyū-buntansha): SAITO Takahiro Utsunomiya University, Fac. of Agriculture, Associate Professor, 農学部, 助教授 (50221990)
• Project Period (FY): 2000 – 2002
• Keywords: Hydroponics / Organic culture medium / water circulation / 3 phase distribution / Komatsuna / root area control

Research Abstract

We tried to use the bark culture medium called as "Bark de Green" as the organic culture medium in place of the rockwool, and designed control system of root area environment of plant, which aimed at the circulation and re-use of cultivating nutrient water.
The bark consisted of Japan ceder and Japanese cypress was divided to 2 classes of under 10 mm and over 10 mm by size, and 6 categories were made by the mixing rate of the bark size. The physical properties of bark culture medium were measured on 3 phase distributions, density, and water content. Also tomato and komatsuna were cultured in capillary watering system.
1. As the ratio of bark under 1 mm increased, solid phase and liquid phase increased, and then gas phase decreased. As compared with rockwool, the liquid phase was low, and decreased as pF value was higher from pF 1.0. But the bark had as same liquid phase as rockwool below pF 0.9 when the ratio of size under 1 mm was more than 80 %. Water holding performance of bark culture medium was lower than that of rockwool.
2. In tomato culture, there ware no obvious differences in growth between the bark culture medium with 80 % or under of ratio of bark under 1 mm and rockwool. Therefore the bark with those sizes was as useful as rockwool in growth of tomatoes.
3. In komatsuna culture, its growth was good at the bark with the size under 1 mm and rockwool at 20 cm height of culture medium. Early growth was lower at the bark size over 1 mm. At the 10 cm height of culture medium bark on the market without size sorting was good balance between liquid and gas phases, and indicated stable growth of komatsuna.
4. The capillary watering system showed the better growth than drip irrigation system at komatsuna culture using organic culture medium, and proved to have high practical use for simple and cheap watering system.