Reseaches On Building And Intial Application On Fish-Vegetable Culture Model

This research was carried on applying floating beds of Ipomoea aquatic Forsskal to traditional fish ponds, established a fish-vegetable culture model to explore a new aquaculture model and maintain good water environment in ponds, conserved water resources and alleviate the pollution with the exchange. The main research contents and main results are summarized as follows:1. Screened out a Ipomoea aquatic Forsskal cultivars suiting to grow in eutrophicated pond water. Experiments were carried out to compare the growth features and water purification efficiency of different Ipomoea aquatica Forsskal cultivars at the floating-bed. Besides small body of water test, the I. aquatica young seedlings were planted in ponds for test. Results show that wide-leaf white-skin I. aquatica is the best breed for its higher growth velocity, longer vegetative cycle and more buds produce which was grown in eutrophication ponds. The small body of water test results show that different I. aquatica cultivars have different ability of eutrophication water quality improvement, the removal rate of NH4+,NO3-,TN,PO43-,TP by wide-leaf green-skin and wide-leaf white-skin I. aquatica are 79.35-91.39%,84.38～85.32%,62.30～68.98%,70.09～85.26%,77.95～78.88%, they are higher than the other two breeds. As a result, wide-leaf white-skin I. aquatica is the best cultivars to apply in the floating-bed for purifying of eutrophicated water bodies in ponds and similar waters.2. Conducted different coverage rate of Ipomoea aquatica Forsskal on fish ponds to test the application effect of floating beds on aquaculture ponds. The results indicated that this plant grown well on the surface of ponds, the max-biomass reached 12.63 kg/m2, moreover, the planted float had a good effect on removing of P (PO43-and TP) and improving water transparency, the effect increased with the coverage of the plant. The specification of harvested fingerlings like grass carp (Ctenopharyngodon idellus).crucian (Carassius auratus), bream fish (Parabramis pekinensis),bighead carp (Arixtichthys nobilis) were bigger in test ponds than in the control pond, because the plants provided a good inhabit and feeding environment with their strong root systems. The best experimental pond (5.0% coverage of Ipomoea aquatica Forsskal) yield is higher 59.1 kilogram per mu than the traditional pond, and obtained extra profit RMB 685.3 yuan per mu. However, this Ipomoea aqautica Forsskal floating beds could decrease the dissolve oxygen levels in the water, had small effect on removal of nitrogen, limited silver carp's (Hypophthalmichthys molitrix) growth. We should pay attention the weakness and applied other combined techniques.3. An experiment was conducted in twelve cement ponds of each 5.0m×3.0m×1.0m in Augt-Sep 2010. This experiment was designed to explore Ipomoea aquatica Forsskal's effect in Carassius auratus culture ponds. There were four treatments in triplicate, four densities of Ipomoea aquatica Forsskal (Og·m-2,250 g·m-2,500 g·m-2 and 1000 g·m-2) were stocked, each treatments with the same densities of carassius auratus (5ind·m2), all the treatments took the same management. Results showed that:①All the group's carassius auratus's daily weight gain, survival rate, feed coefficient were no significant each other, these illustrated the plant's in ponds had no impact with yields of carassius auratus.②In experimental period, it observed that the lower concentration of NH4+,UIA,TN,PO43-,TP in fish-vegetable polyculture group's than control's significantly, transparency in polyculture group were higher significantly than control's, however, Dissolved Oxygen and pH in polyculture group were lower significant than control's. Methods Hierarchical cluster analysis were adopted to evaluate the water quality in the four treatment, the results showed that 1000 g·m-2 Ipomoea aquatica Forsskal's group's water is the best, next to the 500 g·m-2 plant's group, Og·m-2 and 250 g·m-2 plant's water quality were the worst. This means Ipomoea aquatica Forsskal have good efficacy for purification of pond water, the effect increases with the density of plants.③Ipomoea aquatica Forsskal could absorb great quanlitilies of N and P nutrients, and promoted the total utilization ratio of N and P from fish diets. The hightest total N and P utilization group was the 1000 g·m-2plants treatments, they increased by 1.19 and 2.75 times than the control's. Quadratic regression equations were simulated between plant's weight:fish weight and N, P utilization, the results showed that the optimum stocking ratio of Ipomoea aquatica Forsskal:carassius auratus was 1.62-1.85:1.