04aE14P
水中気泡内放電を用いた植物の育成改善
Improvement of Growth Rate of Plants by Discharge inside Bubble in Water
髙畑純一郎1, 高木浩一1, 颯田尚哉2, 山田修3, 藤尾拓也3, 佐々木裕二3, 高橋克幸4
TAKAHATA Junichiro1, TAKAKI Koichi1, SATTA Naoya2, YAMADA Osamu3,
FUJIO Takuya3, SASAKI Yuji3, TAKAHASHI Katsuyuki4
1

岩手大工, 2岩手大農, 3岩手県農業研究センター, 4シシド静電気
1,2Iwate Univ, 3Iwate Agricultural Research Center, 4Shishido Electrostatic, LTD.

0.3

60.25

5Log CFU/mlDry weight [g]Discharges in water are one of the promising candidates to reduce the infection risk of plants inhydroponics because the discharges produce chemical active species such as atomic oxygen (O), ozone (O3)and hydroxyl radical (OH), which work to inactivate the sundry germs [1]. In addition, the discharges also
produce nitric acids which are working as fertilizer [2]. In this study, the effect of the discharge irradiation to
the water on bacteria activity and growth rate of the plants were evaluated. In the experiments, Fragaria ×ananassa, Spainacia oleracea and Raphanus sativus var. sativus plants were cultivated in pots filled withartificial soil, which included the use of chicken droppings as a fertilizer [3]. The water was recycled once
per day from a drainage water pool added to the bed-soil in the pots. A magnetic compression type pulsed
power generator was used to produce underwater discharge with 250 pps in repetition rate. The plasma
irradiation times were set in range from 15 to 30 minutes per day over 28 days of cultivation.
Figure 1 shows the dried weights of cropped Spainacia oleracea at 28 days after cultivation for various
discharge irradiation times. The error bars show the standard deviations of the data. The dried weight of theplant without the plasma irradiation was an average weight of 0.036 g. The dried weight increased to 0.170
and 0.209 g as a result of 15 and 30 minutes of discharge irradiation, respectively. These values correspondto 4.7 and 5.8 times incremental increases in comparison to that of the control group. The statisticalsignificance was confirmed by t-test with an accuracy of P < 0.01. These results indicate that the nitric acids
are produced with the discharges and are absorbed by the roots as a fertilizer [3, 4]. An increment of relative
chlorophyll content of the leaves by the water discharge was also confirmed based on chlorophyll gauge
analysis [3]. Figure 2 shows the time history of the bacteria count in the drainage water of cultivatedRaphanus sativus var. sativus at different discharge irradiation times. The bacteria count was found toincrease from 3.5 to 4.5 Log-CFU at 28 days of cultivation without discharge irradiation. However, thebacteria count in the drainage water after 28 days of cultivation shows approximately the same value at day 0of cultivation under the discharge irradiation condition. The bacteria count decreases by 2 Log-CFU with theapplication of plasma irradiation into the drainage water.

0.2
0.15
0.1
0.05

4321000

control
15 min discharge
30 min discharge
just after 15 min discharge
just after 30 min discharge

1428 (day)Fig. 1. Dry weight of Spainacia oleracea at harvesting time. Fig. 2. Bacteria count in aerobic plate counting agar incultivation of Raphanus sativus var. sativus.
control

15 min discharge

30 min discharge

References[1] T. Ohshima, K. Sato, H. Terauchi and M. Sato: J. Electrostatics. 42 (1997)159.
[2] T. Shigemitsu: J. Plasma Fusion Res. 75 (1999)659.
[3] J. Takahata et al. : IEEJ Trans. FM. 133(2012)211.
[4] K. Takaki et al. : Journal of Physics. Conference Series 418 (2013).