No3
-N content in plant
Figure 6 shows the No
3
-N content by lettuce plants at the end
of the growing period as estimated from the dry weight of the entire
plant and nutrient concentration. The No
3
-N content was significantly
increased in nutrient solution over those of effluent fish water. The
No3
-N content was 227.23 and 107.81 g plant
-1
for nutrient solution
and effluent fish water, respectively. The No
3
-N content was decreased
with increasing the flow rate and length of gully. The No3
–N content
significantly decreased from 241.07 to 208.62 mg plant
-1
(13.46%) in
nutrient solution and significantly decreased from 113.55 to 96.74
mg plant-1
(14.80%) in effluent fish farm at 1 and 2 L min
-1
flow rate,
respectively. The No
3
-N content significantly decreased from 245.82
to 212.05 mg plant
-1
(13.74%) in nutrient solution and significantly
decreased from 115.66 to 103.17 mg plant
-1
(10.80%) in effluent fish
farm at 2 and 4 m length of gully, respectively.
That is to say, No3
–N content in plants grown in nutrient solution
was almost 2 times of that in those grown in effluent fish water. This
may be due to high concentrations of nutrient solution as compared
with those of effluent fish farm.