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The Effect of pH, Nutrient Level and Herbicide Treatment on the Growth of Water Hyacinth [Eichhornia crassipes (Mart.) Solms]
Thesis Abstract:
The photosynthetic rate water hyacinth plants was measured with the use of URAS infra red gas analyzer at constant CO2 concentration of 400 ppm, 25°C and 70% relative humidity. The photosynthetic rate was found to vary from 1.61 to 15.52 mg CO2 dm-2hr-1 when light intensity varied from 7.52 to 36.86 klux, with CO2 compensation concentration of 60 ppm.
Pot experiments using 0.25 strength Hoagloand’s solution demonstrated photosynthate translocation to growing points of the plant, with the highest percentage in the stolon.
Increasing concentrations of nitrogen, phosphorus and potassium resulted in increased dry matter accumulation, stolon number and mean relative growth rate of the plants.
Application of U 44, 08 up to 1 kg/ha stimulated stolon production instead of killing the water hyacinth. Foliar application of 2,4-D amine at 1-2 kg/ha and glyphosate at 1 kg/ha killed the plants but failed to do so when applied through the roots.
Under full sunlight, foliar application of cyanatryn at 2 kg/ha produced photoxicity symptoms the next day and killed the plants in a week. Under 25% light intensity, however, the symptoms appeared 3 days after treatment, and the plants died in 2 weeks.
Cyanatryn application at 2 kg/ha followed by replacement of the culture solution after 2 and 4 hours or washing of the leaves after foliar treatment still killed the plants 14 days later. However, root application of cyanatryn at 1 kg/ha followed by replacement of the culture solution resulted in recovery of the plants 2 weeks after treatment.
Exposure of plants to root application of cyanatryn at 0.25 and 0.050 kg/ha for 3 hours under 25% sunlight intensity stimulated dry matter accumulation, but 50% light intensity did not affect it and full sunlight reduced it.
Plants treated with low nitrogen concentrations (1-5 ppm) of the culture solution accumulated less dry matter than those with high concentration (9 ppm). Also, the former were killed faster than the latter by cyanatryn applied at 0.50-1.00 kg/ha.
Results indicate that the best herbicide treatment is foliar application of cyantryn at 2 kg/ha during high light intensity and under low nitrogen status of the growth medium.