Agriculture Reference
In-Depth Information
agriculture. In the paper, the research progress of nano-TiO
2
utilization in soil
and water remediation, pathogen treatment and decomposition of phytotoxic
substances from straw and cultivated vegetables was collected, highlighting
the phytocatalytic function of nano-TiO
2
utilization in sustainable agriculture.
1.
D
ETOXIFICATION OF
H
ARMFUL
C
OMPOUNDS IN
S
OILLESS
C
ULTIVATION OF
V
EGETABLES
Soilless cultivation of vegetables under cover has gradually become the
prevailing method to produce the off-season vegetables worldwide for its
advantages feasible control of crop growth and the ease of expanding the scale
of cultivation
[1]
. In order to reduce environmental risks caused by wastes
producted in and after soilless culture, a closed hydroponic cultivation systems
is increasingly adopted in practice using organic substrates, such as rice hull
and maize straw. The closed hydroponic cultivation systems can recycle the
nutrient solution to avoid releasing the waste nutrient solution from the
viewpoint of conservation-oriented cultivation. Simultaneously, organic
substrates are more environmentally friendly for their degradable
automatically in nature. However, some researcher found that there are some
phytotoxic compounds released from roots cultured hydroponically [2,3].
Also, organic substrates, e.g. rice hull, gave rice to organic toxic substances
[4]
.
Phytotoxic compounds would inhibit the growth and resultant yield decrease
of vegetables when they accumulated up to high levels. The inhibitory effects
will be more serious for the closed hydroponic cultivation systems because the
nutrient solutions were reused all along [5].
The phytotoxic compounds from organic substrate or secreted from crop
roots were successfully decomposed using the photocatalytic function of nano-
TiO
2
[4,6]. Sunada et al. (2008)
[6] investigated the effects of TiO
2
photocatalytic decomposition and detoxification of phytotoxic compounds
released by the roots of asparagus (
Asparagus officinalis
L.). The
phytotoxically active fraction was extracted either from dried asparagus roots
or from the recycled nutrient solution of an asparagus hydroponic cultivation
system. They found that the phytotoxic activity gradually decreased in the
fraction with TiO
2
powder under irradiation with ultraviolet light at intensity
of 1.0 mW/cm
2
. The growth of asparagus plants under actual cultivation
conditions was also investigated by comparing asparagus grown in a
hydroponic
system
where
recycled
waste
nutrient
solution
was
