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Abstract
SUMMARY
This study was carried out at a private fish farm in Kafr EI-Shikh Governorate to determine the potential of liquid fertilizer utilization in aquaculture and to compare the liquid fertilization program to granular fertilization program and to evaluated the optimal fertilizing rate and to determine the best fertilization frequency. Also, the study investigated the effect of different fertilization program on water quality, growth, fish performance and feed utilization. This study included all growth stages of sex-reversed Nile tilapia Oreochromis niloticus from the larvae of 0.097 ± 0.023g initial weight to marketable fish size. Four experiments were carried out to achieve the aims mentioned above.
The first experiment was conducted to compare the use of granular fertilizers at high level to liquid fertilizers using half of this level. Sex-reversed Nile tilapia of an average weight 40.2±0.18g were stocked at 9000 fish per feddan in six earthen ponds of 1 feddan and fed on 20% crude protein feed at satiation rates. All ponds were fertilized with chicken litter at the rate of 200kg / feddan /2weeks. Three treatments were used in this experiment each in two replicates: Granular fertilization at high level (0.147 mg N + 0.5 mg P2O5/L/2 weeks) by adding 1.33 kg urea + 13.55 kg mono superphosphate/feddan/2weeks plus chicken litter, Liquid fertilization at low level (0.074 mg N + 0.25 mg P2O5 /L/2 weeks) by adding a liquid fertilizer of N:P2O5 : K2O (10-34-0) on the rate of 3.15 kg/feddan/2weeks plus chicken litter and chicken litter only.
The highest total phosphorus value (1.036 mg/L)was found with high level granular fertilization while the highest available orthophosphate (0.371 mg/L) was found with low level liquid fertilizer.
The highest final body weight value (222.62g) was found with chicken litter and artificial feed only, while the intermediate value was in the granular fertilization treatment, and the lowest value was in the liquid fertilizer treatment. The same trend was found with the daily gain. Feed conversion ratio(FCR) improved significantly with liquid fertilization. FCR value with liquid fertilizer was less than its value with granular fertilizers. The highest FCR was found with the third treatment without chemical fertilizers. Protein efficiency ratio (PER) increased significantly in chemical fertilization treatments than its value at the control treatment. It was found to be 3.74, 3.85 and 3.07 for granular, liquid and chicken litter treatments, respectively.
The highest total yield value (2012.5 kg/feddan) was found with liquid fertilization treatment. The lowest total yield value (1843 kg/feddan) was found with granular fertilization treatment.
Differences among treatments in survival rate and in fish content of protein, lipids, moisture were not significant.
The second experiment was carried out in ten earthen ponds of 1 feddan to find out