Keywords

Periphyton; Plankton; Cattle dung; Poultry manure; Press mud.

Introduction

Pond fertilization is a common practice in aquaculture aimed at increasing the production of natural food for farmed fishes. Inorganic fertilizers are expensive and their use by smallholder farmers may be limited [1]. Animal wastes are widely used in many countries to sustain pond productivity at a low cost [2, 3]. Organic fertilizers decompose and release nitrogen, phosphorous and potassium which are used by phytoplankton for growth and reproduction. In addition, they provide attachment sites for bacteria and other microscopic organisms.

Plankton perform other important functions in pond aquaculture - a net producer of dissolved oxygen, which is indispensable for fish growth [4] and the most important sink of ammonia-nitrogen, which is excreted by fish [5, 6]. Jhingran [7] observed that natural food also supplies certain digestive enzymes that improve the utilization of artificial diets.

The FAO/AADCP Regional Expert Consultation has emphasized the need for a greater understanding of the role of natural food organisms in semi-intensive farming based on systems that optimize pond fertilization [8]. Judicious organic fertilization of fish ponds can eliminate the need for supplementary feeding [9]. The use of manures such as poultry manure, dung from cow, sheep, goat or pig is well established [10-16]. In India, cattle manure is frequently used in commercial ponds due to its low cost and easy availability [17, 18]; it plays an important role in the enhancement of fish production by providing major nutrients for the augmentation of phytoplankton- zooplankton food chain. Among the organic manures, poultry manure is considered to be the best since it contains more N and P, which play a vital role in plankton production [19]. Poultry manure is now widely used in commercial freshwater aquaculture. Press mud, a sugar factory waste, is a good source of organic matter. It is rich in potash and phosphorus and is used as manure in agriculture [20]. With a conservative yield of 2% and a total production of 1700 million t of sugarcane in 2009 [21], the world output of press mud can be estimated to be about 30 million t.

Facilitating the growth of periphyton by installing substrates in ponds adds a new dimension to natural food production. Periphyton is readily consumed by browsers such as rohu and fimbriatus and is also helpful in improving water quality by producing oxygen, trapping suspended solids and taking up ammonia and nitrate. Studies have demonstrated comparative growth of carps in periphyton-based systems and feed-driven systems [22-24].

Although some investigations have been performed on the effect of fertilizers on plankton production [25, 26], comparative studies on the effect of poultry manure, cattle dung and press mud on the growth of periphyton are lacking. Therefore, the present study was undertaken with the aim of determining the effect of these manures on the quantity and quality of periphyton grown on sugarcane bagasse and also plankton biomass in the tanks.

Materials and Methods

Tank preparation

This experiment was conducted for 90 days in nine out-door, soil-based (10 cm), cement tanks of 4 × 4 × 1 m. Locally available manures, cattle dung (CD), poultry manure (PO) and pressmud (PM) were used for evaluation. While cattle dung was applied as per recommendations for periphyton-based aquaculture [27], the quantity of poultry manure and press mud was calculated based on their nitrogen content, estimated by Kjeldahl method. All the three manures were applied at iso-nitrogenous levels. The fortnightly doses of CD, PO and PM worked out to 7.2, 1.35 and 2.15 kg 16 m-2 tanks. Triplicate tanks were used for each manure treatment. Sugarcane bagasse was suspended vertically using nylon rope at 2 tha-1 for periphyton growth [28]. The tanks were filled with water from a bore well and the level was maintained at 90 + 2 cm. Evaporation loss was compensated fortnightly.

Water quality measurements

Dissolved oxygen, pH, temperature, total alkalinity, transparency, nitrate, total ammonia and phosphate content of tank water were estimated at 09.00 hronce in ten days, following standard procedures [29].

Biochemical analyses

Representative samples of cattle dung, poultry manure and press mud was analysed using standard methods. Analysis of dry matter was done by drying pre-weighed samples in an oven at 100°C for about 16 h to reach a constant weight. Nitrogen was analysed using Kjeldahl method, and phosphorus and potassium using spectrophotometry and flame photometry. From each tank, quantitative periphyton samples were collected in triplicate at 15 day intervals by carefully scraping the hard surface area (10 × 10 cm) from three bundles of bagasse using a blade. The samples thus collected were used for the analysis of chlorophyll-a, biomass (dry weight) and proximate composition parameters viz. moisture, crude protein, crude fat, crude fibre, ash and nitrogen-free extract [30]. Crude protein content of dry matter was calculated using the nitrogen to protein conversion factor of 5.8 suggested by Gnaiger and Bitterlich [31], who found this to be a more appropriate value for bacteria, algae and aquatic invertebrates than the 6.25 that is usually applied. The gross energy content was calculated using values of 22.6 kJg-1 for protein, 38.9 kJg-1 for lipid and 17.2 kJg-1 for carbohydrate as nitrogen-free extract (NFE) [32]. Plankton biomass of the tank water was also analyzed at 15 day intervals by filtering 100 litres of water through bolting silk cloth of 15 μm mesh size. The samples were subjected to proximate composition analysis as that of periphyton.

Statistical analysis

Data on periphyton and plankton was compared employing one-way analysis of variance. Pair-wise comparison of treatment means was done by Duncan’s multiple range test (P=0.05) [33], when a parameter was significant.

Results

The nutrient composition of manures used in the study is given in Table 1. While poultry manure had higher NPK content, cattle dung and press mud had almost similar values. The results of water quality analyses are depicted in Figure 1. All the parameters monitored showed significant variation during the experimental period. Water pH increased with the experimental duration. Tanks applied with cattle dung recorded lower (P>0.05) pH and those receiving poultry manure showed higher (P>0.05) phosphate content. Other parameters did not show any significant variation among the different treatments.

Figure 1: Water quality parameters in tanks receiving different manures.

Table 1: Major nutrient composition (%, Mean ± SD on dry weight basis) of the organic manures applied in experimental ponds.

Total pigment content and biomass of periphyton (dry matter) and plankton (dry matter) showed higher values in poultry manure treatment (Figure 2). Pressmud treatment recorded lower plankton dry matter. The increase in periphytic biomass stabilized at 75 days of experiment.

Data on proximate composition analysis of periphyton and plankton is given in Tables 2 and 3, respectively. Crude protein content was higher (P<0.05) in periphyton from poultry manure treatment. Other parameters showed no difference (P>0.05) among periphyton from different treatments. The proximate composition of plankton also showed higher crude protein, crude fibre and ash values in poultry manure compared to other manures.

Table 2: Proximate composition (%, Mean ± SD on dry weight basis) of periphyton, values with the same superscript in each column
are not significantly different (P>0.05).

Table 3: Proximate composition (%, Mean ± SD on dry weight basis) of plankton, values with the same superscript in each column are
not significantly different (P>0.05).

Discussion

Fluctuations in dissolved oxygen were less under poultry manure treatment with consistent lower values, compared to other treatments. This may be attributed to the higher demand for oxygen during morning hours by the higher load of planktonic and periphytic organisms in the treatment (Figure 2). A decrease in dissolved oxygen following organic manuring has been demonstrated in earlier studies [34-36].

Figure 2: Total pigment content (A), biomass (dry matter) of periphyton (B) and biomass (dry matter) of plankton (C) (Mean ± SD) recorded in different treatments.

Excepting on day 70, the transparency of water was lower under PM treatment, compared to the other treatments, though the treatment recorded lower plankton dry matter. Boatong et al. [37] recorded no significant variation in transparency among the ponds fertilized with cattle dung and poultry manure though there was higher phyto and zooplankton production with the latter. Lower pH in ponds fertilized with cattle dung compared to those with poultry manure as observed in the present study was also reported by Boatong et al. [37]. Cattle dung is known to reduce pH when applied to fish culture ponds [38].

The mean periphyton biomass recorded in the present study (7.1, 6.1 and 5.0 mg cm-2 in poultry, cattle dung and press mud, respectively) was higher than that in grazed systems [39-41]. This may be attributed to the absence of periphyton grazers. The decomposition of organic manure in fish pond is carried out by bacteria, fungi and actinomycetes [42, 43]. Periphytic biota, including these organisms would have contributed to higher nutrient release for periphytic growth.

Manures have been found to influence the natural productivity differently in terms of abundance and prevalence of phyto and zooplankton as well as the benthic organisms in ponds. According to Liebig’s Law of the Minimum [44], plant growth is limited by the nutrient present in shortest supply relative to its need by phytoplankton. Phytoplankton and other aquatic plants are limited most commonly by inadequate nitrogen and phosphorus supply. Since all the treatment tanks received manures at iso-nitrogenous level, the variation in periphytic and planktonic quantity recorded in the present study is attributable to phosphorus content. Phosphorus, though required in small quantities for aquatic biota, is the single most important element in water, because of its necessity for plankton growth. Poultry manure is a rich source of phosphorus compared to other manures (Table 1). The availability of all the inorganic nutrients from poultry manure was reported to be considerably higher than that from cattle manure [45]. Studies comparing different organic manures, including poultry manure and cattle dung, for plankton production have revealed that poultry manure is the best among them [10, 19, 46, 47]. Lahiri et al. [48] also reported higher planktonic density in ponds applied with poultry manure compared to cattle dung, indicating that gross primary productivity and plankton volume in the culture units were the direct functions of phosphate concentrations.

Keshavanath et al. [49] recorded higher plankton biomass in press mud applied ponds compared to cow dung treated ponds. However, in the present study, the plankton biomass was the lowest under press mud treatment. In spite of reports on beneficial effects of press mud, disadvantages of press mud are also presumed [50]. If press mud is directly applied to soil as manure, the wax present might deteriorate the physical properties such as permeability, aeration, soil structure, composition, etc. and with the passage of time the deterioration might worsen. Solaimalai found that press mud application to rice crop did not influence the production. In soybean cultivation, press mud application reduced seed yield compared to enriched farm yard manure [51]. However, seed yield and protein content increased when press mud was applied along with recommended fertilisers [52]. These results indicate that the beneficial effect of press mud alone as manure is not universal.

The mean total pigment content in periphyton was 16.0 from PO treatment compared to 15.7 from PM and 12.6 μg cm-2 from CD. Kong’ombe et al. [53] recorded higher chlorophyll content of plankton under PO manuring compared to CD, indicating that there was a higher level of phytoplankton production in the former. The pigment content of periphyton showed an increasing trend up to 45-60 days and then decreased in all the treatments. This may be attributed to decreased productivity of older periphyton [54]. Continuous grazing results in higher periphyton productivity [55]. Since fish were absent in this experiment, only minimal grazing would occur by zooplankton, molluscs and other invertebrates.

The crude protein (CP) and fat contents in periphyton were lower (CP 23.90 to 27.02%; fat 1.78 to 2.36%) than that of the plankton (CP 28.11 to 32.41%; fat 4.28 to 5.32%). Azim [27] also recorded slightly higher nutritional value for plankton (27-50% protein, 2-5% lipid, 8-24% ash and 18-23 kJ g^-1 energy) than periphyton. Hepher [56] reported 18-31% protein, 4-10% lipid and 27-48% ash (on dry matter basis) for planktonic algae in ponds depending on the taxonomic group. Proximate composition of periphyton from different substrates varied from 9-32% protein, 2–9% lipid, 25–28% NFE and 16–42% ash [57]. Our earlier findings with periphyton from sugarcane bagasse grown with poultry manure revealed the following proximate composition: crude protein 26.06%, lipid 3.08%, NFE 38.02% and ash 17.45% [58]. Excepting for ash and NFE, the other parameters were comparable to the values obtained in the present study. The ash content of the periphyton did not vary between treatments, but varied between periphyton and plankton, with lower values in the latter. The ash content of periphyton ranged between 36.21 to 38.20% as against 21.29 to 24.48% in plankton. Azim et al. [57] recorded 41% ash from hizol substrate. Ash content was higher in the absence of grazing by fish [55, 59]. As observed in the present study, Kong’ombe et al. [53] also reported higher ash, protein and energy contents for zooplankton under poultry treatment, compared to cattle dung. The higher crude fibre content in periphyton samples compared to that in plankton is an indication of higher biomass of algal species in periphytic biomass, compared to free plankton as reported earlier [24].

Conclusion

Among the three manures compared, poultry manure performed better. Boyd and Hossain [60, 61] reported that despite iso-phosphorus content, the nutrient status of poultry manure is superior to cattle dung or inorganic fertilizers when these are used alone. Not only the amount of phosphorus is high in poultry manure compared to cattle dung, but also the availability in inorganic form which is more easily available than the organic form (90% compared to 75% in cattle dung). Further, poultry manure contains easily decomposable components most of which are in the form of urea and uric acid [62]. Poultry manure had the highest levels of total N, P and narrowest ratios of C/N and C/P, suggesting superior mineralization of organic forms of N and P from it, compared to dairy cow manure [62]. The nutrient composition of cattle dung and press mud were similar. Reflection of this could be seen in their more or less similar performance.

The results of the present study indicate that poultry manure is superior to cattle dung and press mud when used in a periphyton based aquaculture system.

Acknowledgement

The authors are grateful the Department of Biotechnology, New Delhi for funding support through project No. BT/ PR5388/AAQ/3/594/2012.

References

1. Swift DR (1993) Aquaculture training manual, 2nd edition. Fishing News Books, Garden Walk Farnham, Surrey, UK p: 158.
2. Peker F, Olah J (1990) Organic fertilization. In: Proceedings of FAO-EIFAC symposium on production enhancement in still water pond culture. Berka R, Hilge V (edtrs), Prague, Czechoslovakia, pp: 116-122.
3. Knud-Hansen CF (1998) Pond fertilization: Ecological approach and practical application. In: Pond Dynamics/Aquaculture Collaborative Research Support Program, Oregon State University, Corvallis, OR, USA, p: 125.
4. Teichert-Coddington D, Green BW (1993) Tilapia yield improvement through maintenance of minimal oxygen concentrations in experimental grow-out ponds in Honduras. Aquaculture 118: 63–71.
5. Hargreaves JA (1998) Nitrogen biogeochemistry of aquaculture ponds. Aquaculture 166: 181–212.
6. Jiménez-Montealegre R (2001) Nitrogen transformation and fluxes in fish ponds: A modelling approach. PhD dissertation. Wageningen University.
7. Jhingran VG (1982) Fish and fisheries of India, 2nd edn. Hindustan Publishing Corporation, New Delhi, India.
8. NACA/FAO (2000) Aquaculture development beyond 2000: The Bangkok Declaration and Strategy. Proceedings of the Conference on Aquaculture in the Third Millennium, 20-25 February 2000, Bangkok, Thailand. NACA, Bangkok and FAO, Rome, p: 471.
9. Moav R, Wohlfarth G, Shroeder GL, Hulata G, Barash H (1977) Intensive polyculture of fish in freshwater ponds, 1: Substitution of expensive feeds by liquid cow manure. Aquaculture 10: 25-43.
10. Banerjee RK, Roy P, Singit GS, Dutta BR (1979) Poultry droppings its manurial potentiality in aquaculture. J Inland Fish Soc India 11: 104-108.
11. Jhingran VG, Sharma BK (1980) Integrated livestock-fish farming in India. In: Integrated agriculture aquaculture farming systems, Pullin RSV, Shehadeh ZH (edtrs). ICLARM Conf Proc 4: 135-142.
12. Garg SK, Bhatnagar A (2000) Effect of fertilization frequency on pond productivity and fish biomass in still water ponds stocked with Cirrhinus mrigala (Ham). Aquacult Res 31: 409-414.
13. Dhawan A, Kaur S (2002) Pig dung as pond manure: Effect on water quality, pond productivity and growth of carps in polyculture system. Naga 25: 11-14.
14. Das PC, Ayyappan S, Jena J (2005) Comparative changes in water quality and role of pond soil after application of different levels of organic and inorganic inputs. Aqua Res (CIFA) 36: 785-798.
15. Bwala RL, Omoregie E (2009) Organic enrichment of fish ponds: Application of pig dung vs. tilapia yield. Pakistan J Nutr 8: 1373-1379.
16. Priyadarshini M, Manissery JK, Gangadhar B, Keshavanath P (2011) Influence of feed, manure and their combination on the growth of Cyprinus carpio (L.) fry and fingerlings. Turkish J Fish Aquat Sci 11: 597-606.
17. Kamanga L, Kaunda E (1998) The effect of different types of manure on zooplankton abundance and composition in relation to culture of Oreochromis shiranus (L). In: First Regional Workshop on Aquaculture. Proceedings of the First Workshop on Aquaculture. Likongwe JS, Kaunda E (edr), University of Malawi, Lilongwe, pp: 45-56.
18. Garg SK, Bhatnagar A (1999) Effect of different doses of organic fertilizer (cow dung) on pond productivity and fish biomass in still water ponds. J Appl Ichthyol 15:10-14.
19. Dhawan A (1986) Changes in the tissue composition and reproductive cycle in relation to feeding in major carp Cirrhinus mrigal (Ham.) Ph.D. Thesis PAU. Ludhiana, India.
20. Diaz PM (2016) Consequences of compost press mud as fertilizers. DJ Int J Adv Microbiol Microbiol Res 1: 28-32.
21. FAO (2011) Joint FAO/WHO food standards programme codex committee on contaminants in foods, Fifth Session, pp: 64–89.
22. Keshavanath P, Gangadhar B, Ramesh TJ, van Dam AA, Beveridge MCM et al. (2002) The effect of periphyton and supplemental feeding on the production of indigenous carps, Tor khudree and Labeo fimbriatus. Aquaculture 213: 207-218.
23. Keshavanath P, Gangadhar B, Ramesh TJ, van Dam AA, Beveridge MCM et al. (2004) MCJ Effects of bamboo substrates and supplemental feeding on growth and production of hybrid red tilapia fingerlings (Oreochromis mossambicus X O. niloticus). Aquaculture 235: 303-314.
24. Gangadhar B, Sridhar N, Umalatha, Raghavendra CH, Santhosh HJ, et al. (2016) Growth performance and digestive enzyme activities of fringe-lipped carp Labeo fimbriatus (Bloch, 1795) in periphyton based nursery rearing system. Indian J Fish 63: 125-131.
25. Wahab MA, Kibria MG (1994) Katha and kua fisheries-unusal fishing methods in Bangladesh. Aquacult News 18: 24.
26. Ahmed GU, Hossain MAR, Wahab MA, Rahman KMA (1997) Effect of fertilizers on soil and water quality parameters and growth of a carp (Labeo rohita, Hamilton) fry. Progr Agric 8: 111-114.
27. Azim ME (2001) The potential of periphyton-based aquaculture production systems. Ph.D. Thesis, Wageningen University.
28. Keshavanath P, Wahab MA (2001) Periphyton-based aquaculture and its potential in rural development. Summary of an EC-INCO-DC funded workshop, p: 58.
29. APHA (1998) Standard methods for the examination of water and wastewater, 20th edn. American Public Health Association, Washington, DC.
30. Hastings WH (1976) Fish nutrition and fish feed manufacture. Paper presented at FAO technical conference on aquaculture, Kyoto, Japan, p: 13.
31. Gnaiger E, Bitterlich G (1984) Proximate biochemical proposition and caloric content calculated from elemental CHN analysis: a stoichiometric concept. Oecologia 62: 289-98.
32. Mayes PA (1990) Nutrition. In: Harper’s Biochemistry 22nd edition. Murray RK, Graner DK, Mayes PA, Rodwell VW editors. Prentice Hall International Inc., USA, pp 571-579.
33. Duncan DB (1955) Multiple range and multiple F-tests. Biometrics 11: 1-40.
34. Chattopadhyay GN, Mandal LN (1980) Inorganic transformation of applied phosphorus in brackish water fish pond soil under different water salinity levels. Hydrobiologia 71: 125.
35. Jhingran VG (1995) Fish and fisheries of India, Hindustan Publishing Corporation, New Delhi, India, p: 615.
36. Pillay TVR (1995) Aquaculture - Principles and practices. Fishing News Books, Cambridge, England, p: 575.
37. Baotong H, Tingting W, Yingxue F, Jiayi D, Xianzhen, G (1983) Preliminary studies on the effects of three animal manure on the ecological conditions of pond water and fish growth, NACA, Bangkok, Thailand.
38. Magada S, Puttaswamy GP, Vasudevappa C (2007) Reclamation of saline/alkaline soils through aquaculture. In: Proceedings of International Conference on 21st Century Challenges to Sustainable Agri-Food Systems, Chengappa PG, Nagaraj N. Kanwar R editors. I.K. International Pub. House, New Delhi, India, pp: 257-260.
39. Azim ME, Wahab MA, van Dam AA, Beveridge MCM, Huisman EA, et al. (2001a) Optimization of stocking ratios of two Indian Major carps, rohu (Labeo rohita Ham.) and catla (Catla catla Ham.) in a periphyton based aquaculture system. Aquaculture 203: 33-49.
40. Azim ME, Wahab MA, van Dam AA, Beveridge MCM, Huisman EA, et al. (2001b) The potential of periphyton-based culture of two Indian major carps, rohu Labeo rohita (Hamilton) and gonia Labeo gonius (Linnaeus). Aquacult Res 32: 209-216.
41. Azim ME, Wahab MA, van Dam AA, Beveridge MCM, Milstein A, et al (2001c). Optimization of fertilization rates for maximizing periphyton growth on artificial substrates and implications for periphyton-based aquaculture. Aquacult Res 32: 749-760.
42. Boyd C.E (1995) Bottom soils, sediment and pond aquaculture. Chapman and Hall, New York, New York, p: 348.
43. Gaur AC, Neelakantan S, Dargan KS Organic manures. Publications and Information Division, Indian Council of Agricultural Research, New Delhi, pp: 159.
44. Odum EP (1975) Ecology: The link between the natural and social sciences, 2nd (edn). Holt-Saunders, New York, p: 244.
45. Kapur K, Lal KK (1986) Relative potency of certain livestock wastes for fish culture. In: Proceedings of First Asian Fisheries Forum, Mclan J, editor. Manila, Philippines.
46. Ray P, David A (1969) Poultry manure as potential plankton producer in fish nurseries. “LABDEV” J Sci Tech, Kanpur, India 78: 229-231.
47. Bhanot K, Basher VS, Bhattacharya M, Ayyappan S, Panil KS (1991) Composted domestic refuse as manure in carp ponds national symposium on new horizons in carp ponds. National symposium on new horizons in fresh water aquaculture, pp: 163-165.
48. Lahiri S, Jana T, Chatterjee J, Jana BB (2014) Assessment of fertilized pond ecosystem productivity using aerobic cellulose decomposing bacteria as carbon signature. Asian Fish Sci 27: 234-247.
49. Keshavanath P, Shivanna, Gangadhara B (2006) Evaluation of sugarcane by-product pressmud as manure in carp culture. Biores Tech 97: 628-632.
50. Bhosale PR, Chonde SG, Nakade DB, Raut PD (2012) Studies on physico-chemical characteristics of waxed and dewaxed press mud and its effect on water holding capacity of soil. ISCA J Biol Sci 1: 35-41.
51. Ramasamy S, Ten Berge HFM, Purushothaman S (1997) Yield formation in rice in response to drainage and nitrogen application. Field Crop Res 51: 65-82.
52. Jain RC, Tiwari RJ, Nema DP (1995) Integrated nutrient management for lentil under rain-fed conditions in Madhya Pradesh II. Nodulation. Nutrient content and economies. Lens Newsletter 22: 13–15.
53. Kang’ombe J, Brown J A, Halfyard LC (2006) Effect of using different types of organic animal manure on plankton abundance and on growth and survival of Tilapia rendalli (Boulenger) in ponds. Aquacult Res 37: 1360-1371.
54. Azim ME, Wahab MA, Verdegem MCJ, Beveridge M (2002) The effects of artificial substrates on freshwater pond productivity and water quality and the implications for periphyton-base aquaculture. Aquat Liv Res 15: 231-241.
55. Huchette SMH, Beveridge MCM, Baird DJ, Ireland M (2000) The impacts of grazing by tilapias (Oreochromis niloticus L.) on periphyton communities growing on artificial substrate in cages. Aquaculture 186: 45-60.
56. Hepher B (1988) Nutrition of pond fishes. Cambridge University Press, Cambridge, UK, p: 385.
57. Van Dam AA, Beveridge MCM, Azim ME, Verdegem MCJ (2002) The potential of fish production based on periphyton. Rev Fish Biol Fish 12: 1-31.
58. Gangadhar B, Keshavanath P (2008) Planktonic and biochemical composition of periphyton grown on some biodegradable and non-biodegradable substrates. J Appl Aquacult 20: 203-232.
59. Makarevich PR, Larionov VV, Druzhkov NV (1993) Mean weights of dominant phytoplankton species of the Barents Sea. Al’gologiya 13: 103–106.
60. Boyd CE (1982) Water quality management for pond fish culture. Elsevier Science Publishers B.V The Netherlands, p: 318.
61. Hossain MY, Begum M, Ahmed ZF, Hoque MA, Karim MA, et al. (2006) A study on the effects of iso-phosphorus fertilizers on plankton production in fish ponds. South Pac Stud 26: 101-110.
62. Maerere AP, Kimbi GG, Nonga DLM (2001) Comparative effectiveness of animal manures on soil chemical properties, yield and root growth of Amaranthus (Amaranthus cruentus L.) African J Sci Tech 1: 14-21.