EFFECTS OF NITROGEN CONCENTRATION AND SHOOT HARVESTING FREQUENCY ON THE REGROWTH OF SHOOT AND DEGENERATION OF ROOT OF WATER HYACINTH (Eichhornia crassipes) GROWN ON POT AT HAWASSA, ETHIOPIA

Abstract

Water hyacinth (Eichhornia crassipes) is a perennial, herbaceous, free-floating, flowering, and invasive aquatic plant of the genus Eichhornia in the Pickerelwe family (Pontederiaceae). Recently, water hyacinth has been considered an invasive aquatic plant in Ethiopia. The main control methods of water hyacinth in Ethiopia are manual harvesting or weed removal by hand. The problem related to manual harvesting: there is no recommended harvesting schedule concerning the regeneration potential of the weed, and there is no integrated management practice. Therefore, a pot experiment was conducted to investigate the effect of nitrogen fertilizer and harvesting frequency on the regrowth of shoot and root degeneration of water hyacinth, to evaluate the response of water hyacinth to different rates of nitrogen fertilizer application, and to evaluate and determine the optimum harvesting frequency that degenerates the regrowth of shoot in water hyacinth under shade house conditions. The treatments comprised a factorial combination of six nitrogen fertilizer levels (0, 20, 40, 60, 80, and 100 mg L -1 ) and four harvesting levels (unharvested, harvested once, harvested twice, and harvested thrice) with three replications. A total of 24 treatment combinations were formed. The pot experiment will be set out as a complete randomized design (CRD). The results revealed that all growth parameters were significantly influenced by the mean factor as well as the interaction. When it comes to root growth, the treatments with 0 and 20 mg L -1 nitrogen treated without harvest had the greatest root length, root diameter, and root number. All gas exchange parameters are also influenced by the interaction effect of the main factor, except leaf relative water potential and stomatal conductance, which are both only affected by the main effect. Chlorophyll a and b and total chlorophyll are only influenced by nitrogen fertilizer. Water hyacinth exposed to frequent harvesting significantly reduced all tested parameters except stolen production. The present result, therefore, indicates that 60 mg/L -1 nitrogen fertilizer is the best for the growth of water hyacinth and that harvesting frequency decreases the regrowth of shoots and degeneration of roots. Therefore, we recommend management practices that reduce water body's pollution and frequency of harvesting to degenerate the root of water hyacinth and its impact on the water bodies