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Abstract The current investigation was carried out to study the effect of organic m a n u re , mineral f e r t i l t z e r s and artificial feed on both different soil properties and fish production. Moreovert the effect of different stoc ing rates on the fish production was also studied. (A) To achieve the first p u rp o se , five ponds in El-$ row Fish Farmt Dakahlia Governoratet were chosen to carr out the following treatments: 1. T e first pond was fertilized with organic manure a ly. 2. T~e second pond was fertilized with two mineral fertilizers i.e ammonium sulphate and superphosphate. 3. T~e third pond was fertil i ze d with organic manure t~gether with mineral fertilizers. 4. A~tificial feed was used in the 4th pond alone. I 5. T~e fi vth pond wa s control t i. e no fert i 1 izers or artificial feeds were used. All these ponds were stocked with Tilapia s pp ., Cyprinus carpio and Mugil cephalus at the rate of 1800 fish per feddan for a growth period of 160 days. To study the effect of di fferent treatments on somej soil physical and chemical properties, soil samples we reii t a ken fro m 0 - 10 , LO- 2 5 and 2 5 - 6 0 c m s 0 i 1 d e p t h 5 at: lt he beginning of the study, after three months and i a t tl h e end 0 f stu dy, i .e aft e r h a r v est i ng the f ish and ! dryilng ponds of the farm. ! Al so, water samples were taken monthly for anal y s ns from the five ponds and from the source and drainage water. In the same time, random samples from all reared fish species were taken and weighted every month from June 1989 to November 1989. The obtained results can be summarized as follows: (I) The effect of di fferent treatments on some soil physical properties: 1. Particle size distribution was not affected by the used treatments. 2. The values of soil bulk density were decreased in all fertilized ponds, except in the pond recieved mineral fertilizers. So i 1 bulk dens i ty increased wi th increasing soil depth. The values of soil bulk density were significantly and negatively correlated with OM%, AS% and EMgP. While they significantly and positively correlated with both of Sol-Na ESP. Moreover, the addition of organic manure with or wi thout mineral fertil izers significantly increased total soil porosity. 3. No clear trend was observed, concerning the effect of different treatments on the values of soil hydrau’iiC conductivity (K). They decreased on most ponds and increased in few ones. 4. The values of DSA% of 4.8-2.5 mm in diameter were increased by the addition of organic manure with or without mineral fertilizers. While, both mineral fertiz1iers and artificial feed did not significantly affected DSA%. On the other hand, a significant and negative correlations were found between DSA% and both of AU and ESP, while the opposite was true for 5. WSA% of 1.6-0.8 mm and 0.8-0.4 mm in diameter were increased by manuring in the surface soil layer, also the WSA% of 0.8-0.4 mm and 0.4-0.2 mm in diameter were increased in the deepest one. It was also found that, the addition of organic manure plus mineral fertilizers raised the values of WSA% of 0.8-0.4 mm and 0.4-0.2 mm in diameter in the surface and subsurfae soil layers.The opposite trend was found in the case of mineral fertilizers and artificial feed where, their additions lowered the WSA% of 0.8-0.4 and 0.4-0.2 mm in diameter in all soil depths. The values of WSA% were significantly and positively correlated with OM%, EMgP and ECaP. While, they significantly and negatively correlated with rc, Bd and ESP. - 174 - 3. Soluble cations and anions: a) Soluble Na was decreased in most experimental ponds especially in the surface layer and in the presence of organic manure. The concentration of Sol-Na at the end of the study was between one to four fivth of the original levels. b) Soluble-K followed nearly the same trend of Sol-Na. c) The changes of Sol-Ca were unlimited, and there was no clear trend concerning the effect of different treatments at the end of study. d) Soluble-Mg was decreased by about 10% to 68.64% at the end of study and as a result of different treatments. e) Soluble-Cl was decreased rapidly in the ponds initially contained high concentration of Cl-, f) There was no measurable amounts of C03, The values of HC03 were decreased in the fertil ized ponds~ while~ they increased in the pond treated with artificial feed in the surface layer. The opposite was true for the deep layers. g) Soluble-S04 decreased in all experimental ponds in all all soil depths. 4. OM% was considerably increased in most ponds, The percentages of increase were 10.31% and 12.22 in the ponds fertilized with organic manure only or organic manure plus mineral fertilizers, respectively. OM% was significantly and positively correlated with AS%, while it negatively correlated with soil pH. 5. The values of soil CEC increased in most investigated ponds, but this increase was not significant. As a general trend, soil CEC increased with increasing soil depth. 6. Soil ESP slightly increased (0.42-15.69%) at the end of study in the pond fertilized with organic manure, while, it decreased by about 4.99 and 50.19% in the other ponds. Similar trend was also noticed for EKP. 7. The values of both ECaP and EMgP were increased in most investigated ponds at the end of experiment. The observed increases of both ECaP and EMg P were correlated with the increases of soluble calcium and magnesium in the pond1s water. ( I I I ) Effee t a f d iff ere n t t rea t men t son f ish production: Results of the first experiment showed that: 1. The growth rates of different fish species reared in the pond fed wi t h art i f i cia 1 feed were higher than that reared in the fertilized ponds. 2. The addition of organic manure to the fish pond gave best production of Mugil cephalus as compared with mineral fertilizers which were not useful. 3. Total fish production of fish reared in the pond fertilized with organic manure plus mineral fertilizers was less than that of the pond treated with artificial feed. But it was higher than the production of the ponds fertilized with either organic manure or mineral fertilizers alone. 4. Statistical analysis showed that, there was no significant difference between the fish production in the pond fertil ized with organic manure alone and that fertilized with organic manure together with mineral fertilizers. The lowest production was obtained in the pond fertilized with mineral fertilizers alone. So it can be said that, the addition of mineral fertilizers to the fish farms is not important. While, it can be recommended the use of organic manure - with care _ in the fish farms instead of the artificial feed to reduce the cost of production. (B) In order to realize the second purpose of the study, i.e. the effect of different stocking rates on fish production. three ponds were chosen. These ponds were stocked with Tilapia spp .• Cyprinus carpio and Mugil cephal us in polyculture system with three different stocking rates i.e, 2100, 3150 and 4200 fish/ feddan. The ratios between the three fish species were 75 : 18.3 and 6.7% for Tilapia Cyprinus carpio and M. cephal us, respectively. The reared f is hes were fed wi th a mi xture of organic manure, mineral fertilizers and artificial feed. The experiment lasted 160 days. The obtained results can be summarized as follows: 1. Growth rates of Tilapia spp. decreased with increasing the stocking rate, while the total production was increased. Statistical analysis showed that, although the final weight of tilapias in the lowest stocking rate was higher than the other two rates, the difference between their final weightrwere not significant. it can be recommended the use of organic manure _ with care - in the fish farms instead of the artificial feed to reduce the cost of production. (B) In order to realize the second purpose of the study, t . e . the effect of different stocking rates on fish p r o duc t t nn , three ponds were chosen. These ponds were stocked with Tilapia spp., Cyprinus carpio and Mug;l cephalus in polycu1ture system with three different stocking rates i.e, 2100, 3150 and 4200 fish/ feddan. The ratios between the three fish species were 75: 18.3 and 6.7% for Tilapia Cyprinus carpio and M. cephal us, respectively. The reared fi shes were fed wi th a mi xture of organic manure, mineral fertilizers and artificial feed. The experiment lasted 160 days. The obtained results can be summarized as follows: 1. Growth rates of Tilapia ~ decreased with increasing the stocking rate, while the total production was increased. Statistical analysis showed that, although the final weight of ti1apias in the lowest stocking rate was higher than the other two rates, the difference between their final weightt!were not significant. |