Methods: The oxygen NB was generated by surface friction and treated in 4 levels:
NB 0% (control, DO 9.21 mg·L−1), NB 20% (DO 15.40 mg·L−1), NB 33% (DO 20.93 mg·L−1),
and NB 100% (DO 39.29 mg·L−1).
Results: The root length of radish and wheat increased more in NB 33% than the control plot.
The fresh weight increased in NB 33% compared to the control plot in radish and wheat, and
both fresh and dry weight increased more in NB 20%, NB 33%, and NB 100% than the control
plot of barley. The leaf length and width of red mustard decreased more in NB 33% and NB 100%
than the control plot and NB 20%, which indicated the leaf compactness. The fresh and dry weight
of shoot and root increased more in NB 100% than the control plot in red mustard. In pak choi,
the shoot fresh weight increased more in NB 100% than the control plot. In leafy vegetables,
the germination rate of red mustard in NB 100% was higher than the control plot, however,
it was not significantly different between oxygen NB plots in sprout vegetables.
Conclusion: The results showed that the root growth and biomass increased after applying
NB 33% in sprout vegetables. The leaf growth properties as the number of leaves and leaf size
were not significantly different or decreased in NB treatments compared to control plots,
but NB 100% (DO 39.29 mg·L−1) effectively increased the root growth and plant biomass in leafy vegetables.
This study could not precisely control the DO for seed germination and leaf growth since
horticultural substrates are used, and did not show a consistent seed germination response
in sprouts and leafy vegetables compared to previous studies using hydroponics. However,
for radish sprouts and wheat sprouts, root length became longer and fresh weight increased
in DO concentration of 20.93 mg·L−1. In leafy vegetables, fresh weight and dry weight increased
in both leafy vegetables and sprouts excluding pak choi, showing that oxygen NB treatment
enables growth stimulation of vegetables. There is a difference in the scope of DO concentration
that enables stable growth of sprouts and leafy vegetables within the scope of oxygen NB
treatment, and for leafy vegetables, the adequate scope of DO concentration is 39.29 mg·L−
