Feeds and Fertilizers

Introduction

Although the PD/A CRSP has conducted many experiments on pond fertilization, research results have differed among sites making the determination of an optimal pond fertilization strategy difficult. Research is necessary to determine the optimum nitrogen, phosphorus, and carbon application rates at the different sites to obtain the optimum fish yield. Thus, the Global Experiment to be conducted as part of this work plan, using a standardized protocol, seeks to identify the optimum nitrogen fertilization rate. Information gathered as part of the pond sediment characterization research or through the water quality and climate monitoring efforts at each site may need to be evaluated in an attempt to determine the causative factors of any site differences observed.

Note: Schedule for FFR1H has been revised. See First Addendum to the Eighth Work Plan
Note: Experimental Design for FFR1K has been revised. See Second Addendum to the Eighth Work Plan
Note: Schedule for FFR1K has been revised. See First Addendum to the Eighth Work Plan and Second Addendum to the Eighth Work Plan
Note: Schedule for FFR1PH has been revised. See Second Addendum to the Eighth Work Plan and Third Addendum to the Eighth Work Plan
Note: Schdule for FFR1T has been revised. See Second Addendum to the Eighth Work Plan

Collaborating Sites
Objectives
Significance
Anticipated Benefits
Identification of Beneficiaries
Collaborative Arrangements
Experimental Design
Identification of Deliverables
Schedule/Time line
References

Collaborating Sites

Honduras
Kenya
Philippines
Thailand

Objectives

1) To determine the optimal rate of nitrogen fertilization (in the presence of adequate phosphorus and carbon) to obtain optimum primary productivity and optimum yields of tilapia in freshwater production ponds.

2) To determine which of the nitrogen fertilization rates evaluated to produce tilapia in freshwater production ponds had the greatest profitability.

3) To develop a full-cost enterprise budget for the fertilization level that results in the greatest profitability.

Significance

Optimization of aquacultural production systems requires optimal use of inputs. Nitrogen, phosphorus, and carbon availability are important considerations in management of ponds for optimum fish production. PD/A CRSP research has addressed enhancement of primary productivity through inorganic and organic nutrient additions to ponds, however our findings on the optimum nitrogen, phosphorus and carbon inputs required to improve fish yields at the PD/A CRSP sites appear inconsistent and demand clarification. Higher nutrient inputs have increased fish production at all PD/A CRSP sites, but optimum inputs of nitrogen, phosphorus and carbon have not been defined (see reports in Egna et al., 1990, 1991; Egna et al., 1992; Egna et al., 1993; Egna et al., 1994, 1995).

Fertilization rates in PD/A CRSP experiments were greater than rates reported for earlier pond fertilization research. In an often-cited series of fertilization experiments conducted in Malaysia, Hickling (1962) never used more than 1.1 kg P and 1.1 kg N/ ha per week. In Israel, the standard fertilizer dose was 2.3 kg P and 6.5 kg N/ha per week (Hepher 1962a, b). The highest rates of phosphorus and nitrogen used in most experiments at Auburn University were 1.26 and 3 kg/ha per week, respectively (Swingle 1947; Boyd l976, l990; Boyd and Sowles 1978; Murad and Boyd 1987). Rates in Europe seldom exceeded 1 kg/ha per week for nitrogen and phosphorus (Mortimer 1954). Rates used in Malaysia, USA, Israel, and Europe were adequate to give dense phytoplankton blooms and good fish production. Also, in all of the studies cited above, phosphorus was the most important limiting nutrient.

Data from these trials will indicate the optimal application rates of nitrogen, phosphorus and carbon to attain the most profitable tilapia yields in tropical freshwater ponds at PD/A CRSP sites. In addition, a full-cost enterprise budget will be developed for the most profitable fertilization rate. Trials will be conducted the warm and cool seasons to determine seasonal effects. Causative factors of any site differences will be investigated based on global ranges of climatic, water quality and soils data.

Anticipated Benefits

This is the first in a series of experiments to determine optimal rates of nitrogen, phosphorus and carbon additions to ponds in order to optimize fish production. Results of these trials will provide N, P, and C application rates to obtain fish yields with the greatest profit. Development of a full-cost enterprise budget for the fertilization rate that results in the greatest profitability will assist host-country and international economists and planners in their evaluation of fish culture systems. Identification of optimal nutrient application rates would reduce the environmental impact of pond effluents.

Identification of Beneficiaries

Small-scale tilapia farmers at PD/A CRSP sites and in countries neighboring PD/A CRSP sites will benefit from the information generated through this research. Aquacultural scientists and students will benefit from this research through an improved understanding of the role of these nutrients in optimizing tilapia production in the tropics. In addition, our research results may be applicable, either directly or with slight modification, to US baitfish and catfish fingerling producers.

Collaborative Arrangements

This research will be implemented at prime PD/A CRSP sites through a collaborative effort of the US and host-country PD/A CRSP participants.

Experimental Design

Sites: Field research facilities at all prime PD/A CRSP sites.

Pond Facilities: Twelve (0.1-ha or size available) earthen ponds.

Culture Period: Variable, until fish growth ceases/carrying capacity attained in all treatments; expected duration approximately 90 days. Expected carrying capacity for this system is 2,000-2,500 kg/ha.

Stocking Rates: Ponds will be stocked with a fish biomass equivalent to 1,000 kg/ha; actual number of fish stocked will depend on initial size. Desired initial stocking size range is 10-50 g/fish. Minimum size at stock is 10 grams.

Water Management: Water will be added to ponds as needed to replace losses to evaporation and seepage.

Other Inputs: Nitrogen, as urea, will be added to ponds at 0, 10, 20 and 30 kg N/ha per week. Phosphorus, as triple superphosphate, will be added to all ponds at 8 kg P/ha per week. Diammonium phosphate also is an acceptable fertilizer source of N and P, in which case urea and triple superphosphate will be used, as necessary, to balance N and P applications. All fertilizer will be dissolved in buckets containing pond water and the fertilizer solution splashed over the pond surface. Initial fertilization of ponds will occur two (2) weeks prior to stocking of fish. All trials will be conducted in ponds with total alkalinity 75 mg/L as CaCO₃. Sodium bicarbonate will be added weekly to attain and maintain the minimum alkalinity (75 mg/L as CaCO₃). Agricultural limestone should be added to ponds to neutralize soil acidity, and also to ensure that total hardness will be similar to total alkalinity; in low-alkalinity ponds, use of sodium bicarbonate can cause high pH under conditions of low hardness.

Test Species: Male Nile tilapia (Oreochromis niloticus) will be stocked into ponds. Sampling Plan: Fish will be sampled by seine net at biweekly intervals to measure growth; approximately 10% of the initial stock will be seined, counted and weighed en-masse. Total nitrogen, total ammonia nitrogen, total phosphorus, Secchi disk visibility, chlorophyll a, total alkalinity, pH and primary productivity (gross and net) will be determined during the 2nd week, midway through the experiment and during the final week according to methodologies detailed in the PD/A CRSP Materials and Methods Handbook. Dissolved oxygen and pH measurements will be taken on the three sample dates at 0600 h, 1000 h, 1600 h, dusk (± 1800 h) and 0600 h the following morning at 5-cm, 25-cm, 50-cm and 75-cm depths in the water column. Weather data is recommended to be collected using a computerized data logger; data should be out-putted as hourly means or totals as well as daily means or totals. If data logging equipment is not available, data should be collected on a daily basis; on the three intensive sampling dates, weather data must be collected and recorded at each of the specified sample times. Ponds will be harvested by draining upon completion of the trial.

Statistical Methods and Hypotheses: A completely randomized design with three replicates per treatment will be used. The null hypothesis is: Increasing rates of nitrogen fertilization do not increase primary productivity and fish yield or affect profitability. Data analysis will be by regression analysis and ANOVA with treatment differences determined by orthogonal contrasts.

Economic Analyses: Partial budget analysis will be conducted to determine which fertilization rate yields the greatest profitability (Kay, 1981). A full-cost enterprise budget will be developed for the fertilization rate that yields the greatest profitability (Kay, 1981).

Identification of Deliverables

Optimal nitrogen application rate, in terms of productivity and profitability, will be identified. A full-cost enterprise budget for the most profitable fertilization level will be developed.

Schedule/Time line

Cool season trial will begin in December 1996; warm season trial will begin in April 1997, or at the beginning of the cool and warm seasons as they occur at the site. Actual implementation schedule depends on date the PD/A CRSP is fully funded and resident researchers are authorized to travel to post, and on completion of necessary logistics for the trial at prime site research stations.

Final Report Submittal: Final report for cool season trial at this site by October 1997; final report for warm season trial by January 1998.

References

Boyd, C. E. 1976. Nitrogen fertilizer effects on production of tilapia in ponds fertilized with phosphorus and potassium. Aquaculture 7:385-390.

Boyd, C. E. 1990. Water quality in ponds for aquaculture. Ala. Agr. Exp. Sta., Auburn University, Ala. 482 pp.

Boyd, C. E. and J. W. Sowles. 1978. Nitrogen fertilization of ponds. Trans. Amer. Fish. Soc. 107:737-741.

Egna, H. S., J. Bowman, and M. McNamara. 1990. Title XII Collaborative Research Support Program Pond Dynamics/Aquaculture seventh annual administrative report 1989. Oregon State University, Corvallis, OR. 114 pp.

Egna, H. S., J. Bowman, and M. McNamara. 1991. Title XII Collaborative Research Support Program Pond Dynamics/Aquaculture eighth annual administrative report 1990. Oregon State University, Corvallis, OR. 166 pp.

Egna, H. S., M. McNamara, and N. Weidner. 1992. Title XII Collaborative Research Support Program Pond Dynamics/Aquaculture ninth annual administrative report 1991. Oregon State University, Corvallis, OR. 172 pp.

Egna, H. S., M. McNamara, J. Bowman and N. Astin. 1993. Title XII Collaborative Research Support Program Pond Dynamics/Aquaculture tenth annual administrative report 1992. Oregon State University, Corvallis, OR. 275 pp.

Egna, H. S., J. Bowman, B. Goetze and N. Weidner. 1994. Title XII Collaborative Research Support Program Pond Dynamics/Aquaculture eleventh annual administrative report 1993. Oregon State University, Corvallis, OR. 178 pp.

Egna, H. S., J. Bowman, B. Goetze and N. Weidner. 1995. Title XII Collaborative Research Support Program Pond Dynamics/Aquaculture twelfth annual administrative report 1994. Oregon State University, Corvallis, OR. 209 pp.

Hepher, B. 1962a. Primary production in fish ponds and its application to fertilization experiments. Limnol. Oceanogr. 7:131-135.

Hepher, B. 1962b. Ten years of research in fish pond fertilization in Israel. I. The effect of fertilization on fish yields. Bamidgeh 14:29-38.

Hickling, C. F. 1962. Fish cultures. Faber and Faber, London. 295 pp.

Kay, R. D. 1981. Farm management: planning, control and implementation. McGraw-Hill Book Company, New York, NY.

Mortimer, C. H. 1954. Fertilizers in fish ponds. Her Majesty's Stationery Office, London, Fish Publ. No. 5. 155 pp.

Murad, A. and C. E. Boyd. 1987. Experiments on fertilization of sportfish ponds. Prog. Fish-Cult. 49:100-107.

Swingle, H. S. 1947. Experiments on pond fertilization. Ala. Agr. Exp. Sta., Ala. Polytech. Inst., Auburn, Ala., Bull. 264. 36 pp.

Feeds and
Fertilizers