Agriculture Reference
In-Depth Information
Cultivation of Plants in the Greenhouse
Sixty subsamples of 300 g soil, i.e., five nanoparticles × three replicates × four
concentrations, were added to square, plastic pots whose length,
width, and height were 8 × 8
× 7 cm, respectively. Specifically, five treatments, comprising nano-Fe
3
O
4
, nano-Fe
2
O
3
,
nano-FeOOH•xH
2
O, nano-TiO
2
, and nano-ZnO at four concentrations of 0.0, 1.0, 3.0, and 6.0
g L
-1
were applied to the soil during irrigation; in essence, we sprayed each plastic pot with
250 mL of 0.0, 1.0, 3.0, or 6.0 g nano L
-1
solution throughout the experiment. We planted
three different seeds for this experiment: sunflower, maize, and common bean; therefore, we
used a total of one hundred eighty plastic pots, i.e., five nanoparticles × three replicates × four
concentrations × three crops. The seeds were placed at a depth of 3 cm in each pot. Five days
after planting, the seedlings were thinned to one plant per plastic pot, and the pots were
placed under greenhouse conditions for 20 days. Although a plastic container was placed
under each pot to collect drained liquid, the irrigation was well controlled, so no leaching was
observed. Twenty days after sowing, three plastic pots were selected at random from each
treatment and concentration. The entire soil column was removed from the pot, and soil
samples were taken at depths of 0.0-3.5 cm and 3.5-7.0 cm, with care not to damage the root
structure. The roots were then separated from the shoots, and the root and shoot lengths were
measured. The roots and shoots were dried at 70 °C, weighed, and analyzed for Ti, Fe, and
Zn. The soil samples from 0.0-3.5 cm and 3.5-7.0 cm were analyzed for pH, EC, Ti, Fe, and
Zn at 0 and 20 days, and the amount of chlorophyll was quantified every two days. The
climatic conditions in the greenhouse were not determined. However, during the experiment,
a similar greenhouse was installed with equipment to monitor its temperature and moisture
content. Its measurements were 32 °C and 47%-50%, respectively.
Chemical Analyses
The pH was measured in 1:2.5 soil or wastewater sludge/H
2
O suspension using a 716
DMS Titrino pH meter (Metrohm Ltd. CH.-901, Herisau, Switzerland) fitted with a glass
electrode (Thomas, 1996). The EC was determined in a 1:5 soil/H
2
O suspension as described
by Rhoades et al. (1989). The organic C in the soil was measured in a total organic carbon
analyzer TOC-V
CSN
(Shimadzu, USA). The inorganic C was determined by adding 5 mL 1
M
hydrochloric acid (HCl) solution to 1 g air-dried soil and trapping the CO
2
evolved in 20 mL
1
M NaOH. The total N in the soil, root, and shoot was measured by the Kjeldahl method,
using concentrated H
2
SO
4
, K
2
SO
4
, and CuSO
4
to digest the sample (Bremner, 1996). Soil
particle size distribution was defined by the hydrometer method as described by Gee and
Bauder (1986). The WHC was measured based on 6.5 kg soil that was placed in a PVC tube
(length 50 cm and diameter 16 cm), water-saturated, stoppered with a PVC ring, and left to
stand overnight to drain freely. The WHC was defined (Gardner, 1986) as described below:
(
)
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