North American Journal of Aquaculture 70:308–313, 2008 Ó Copyright by the American Fisheries Society 2008 DOI: 10.1577/A07-052.1
[Article]
New Nitrogen Fertilization Recommendations for Bluegill Ponds in the Southeastern United States CHRISTOPHER A. BOYD,1 PUAN PENSENG,2
AND
CLAUDE E. BOYD*
Department of Fisheries and Allied Aquacultures, Auburn University, Alabama 36849, USA Abstract.—A nitrogen fertilization experiment was conducted in 33-year-old ponds at the Auburn University Fisheries Research Unit, Auburn, Alabama, after sediment removal and renovation. Twelve ponds were treated with 3 kg P2O5 (1.3 kg P)/ha, and ammonium nitrate was applied to give a range of nitrogen application rates (0–14 kg/ha). The maximum production of bluegills Lepomis macrochirus was achieved at 6 kg N/ha. The optimum fertilizer application rate for ponds from which sediment had been removed was 6 kg N with 3 kg P2O5 (1.3 kg P)/ha, which implies the following ratios: N:P2O5 ¼ 2:1 and N:P ¼ 4.6:1. This fertilization rate should be more appropriate than the commonly used rate of 9 kg N with 9 kg P2O5 (3.9 kg P)/ ha for new ponds in the southeastern United States.
Studies at Auburn University in the 1940s led to the conclusion that the optimal inputs of nitrogen and phosphorus in ponds used to culture sunfish Lepomis spp. were 9 kg N and 9 kg P2O5 (3.9 kg P)/ha (Swingle 1947). Later studies revealed that phosphorus-only fertilization of older ponds resulted in sunfish production similar to that achieved with nitrogen plus phosphorus fertilization (Swingle et al. 1965; Boyd and Sowles 1978; Murad and Boyd 1987). It was proposed that nitrogen mineralization from accumulated bottom soil organic matter and nitrogen fixation by microorganisms provided sufficient nitrogen for good fish production in older ponds with a history of fertilization. Phosphorus also accumulated in pond bottoms, but the amount of phosphorus fertilizer needed to provide good fish production did not decline in older ponds because this nutrient was tightly bound by bottom soil (Swingle et al. 1965). The phosphorus application recommendation was lowered to 4 kg P2O5 (1.75 kg P)/ha by using liquid fertilizers or predissolving granular fertilizers before applying them to ponds (Metzger and Boyd 1980). A study conducted in 2002 by Wudtisin and Boyd (2005) found the optimum phosphorus application rate using liquid fertilizer to be 3 kg P2O5 (1.3 kg P)/ha in ponds that also received 6 kg N/ha per application. A project was initiated in 2004 to remove sediment and renovate older ponds at the Auburn University * Corresponding author:
[email protected] 1 Present address: Coastal Resource and Extension Center, 1815 Popps Ferry Road, Biloxi, Mississippi 39532, USA. 2 Present address: Institute of Agricultural Technology, Walailak University, 222 Thaiburi, Thasala District, Nakhon Si Thammarat, 80160 Thailand. Received June 8, 2007; accepted September 10, 2007 Published online April 14, 2008
Fisheries Research Unit (Yuvanatemiya and Boyd 2006). The present study was conducted to determine the optimum nitrogen application rates for ponds from which sediment had been removed. Methods This experiment was conducted in 400-m2 earthen ponds, each approximately 1 m in average depth, located in the E series at the Auburn University Fisheries Research Unit (FRU). The FRU is about 10 km north of Auburn, Alabama, and is situated at 32.58N latitude. The mean annual temperature is 17.28C (mean minimum ¼ 11.18C, mean maximum ¼ 23.28C). The ponds were constructed in 1971 on acidic, reddish-yellow, podzolic soils of the Piedmont Plateau (McNutt 1981). The water source is a reservoir filled by runoff from a wooded watershed. This water has total alkalinity and total hardness concentrations of 8– 12 mg/L as CaCO3, and nutrient and organic matter concentrations are low (Boyd 1990). Sediment was removed from the ponds in this study in the late summer and fall of 2004 with a Terrex HS41 Walking Excavator (Terrex/Schaeff Group, Langenburg, Germany) as described by Yuvanatemiya and Boyd (2006). Ponds were refilled with water during December 2004. During the study, water was added to ponds to replace evaporation and seepage, but water levels were maintained about 10 cm below the elevation of overflow structures to avoid overflow after rains (Boyd 1982). The total alkalinity concentration in pond waters was measured in January 2005. Ponds with concentration below 25 mg/L were treated in late January with agricultural limestone at 2,000 kg/ha (Boyd 1990). Bluegills Lepomis macrochirus (0.70 g/fish) were purchased from American Sportfish, Montgomery, Alabama, and 200 bluegill fingerlings and five grass
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TABLE 1.—Ammonium nitrate treatment rates and nitrogen inputs per application (kg/ha) and production of bluegills and grass carp (kg/ha) in ponds at the Auburn University Fisheries Research Unit. All ponds were treated with 3 kg P2O5/ha from triple superphosphate. Production Bluegill Pond E E E E E E E E E E E E a
44 39 46 41 43 37 45 47 40 42 48 38
a
Ammonium nitrate
Nitrogen
Large
Small
Total
Grass carp (kg/ha)
0.0 1.5 3.0 6.0 9.0 12.0 15.0 18.0 24.0 30.0 36.0 42.0
0.0 0.5 1.0 2.0 3.0 4.0 5.0 6.0 8.0 10.0 12.1 14.1
55 58 72 52 88 75 60 128 85 85 48 100
102 148 250 218 288 290 275 425 339 225 110 98
158 206 322 270 375 365 335 552 424 310 158 198
102 108 110 108 130 110 112 127 115 95 128 120
Small fish were those less than 6 cm TL, large fish those 10 cm TL or more. The values for large and small fish may not sum to the totals due to rounding.
carp Ctenopharynodon idella (88 g/fish) were placed in each pond on 15 March 2005. The technique of using a wide range of unreplicated fertilizer treatments and analyzing the results by regression analysis to obtain the optimum fertilizer application rate (Wudtisin and Boyd 2005) was used in this study. The experiment consisted of 11 different ammonium nitrate treatments (Table 1) ranging from 0 to 42 kg/ha (0–14.1 kg N/ha). On each fertilization date, all ponds received triple superphosphate at 3 kg P2O5/ha, the optimum phosphorus application rate established for bluegill ponds on the FRU (Wudtisin and Boyd 2005). Fertilizers were weighed and transferred to 20 L of pond water in a plastic bucket. The water was stirred to dissolve the fertilizer, and the resulting slurry was splashed over pond surfaces. Fertilizers were applied 10 times at 3-week intervals between 15 March and 25 September 2005. Water samples were collected with a 90-cm water column sampler (Boyd and Tucker 1992). Samples were taken between 0600 and 0800 hours and midway between fertilization dates. They were transported to the laboratory where analyses were initiated at once. Chlorophyll-a concentration was determined by spectroscopy of acetone extracts of phytoplankton removed from samples by membrane filtration; total ammonianitrogen was measured by the phenate method; total alkalinity was estimated by acidimetry; total hardness was determined by titration with EDTA (Clesceri et al. 1998). Nitrate-nitrogen was determined using the NAS reagent method (van Rijn 1993). Water for total nitrogen and total phosphorus analyses was digested in an alkaline persulfate solution (Gross and Boyd 1998), and the resulting nitrate and phosphate were
measured using the NAS reagent method and ascorbic acid procedure (Clesceri et al. 1998), respectively. In addition, water samples were dipped from pond surfaces on several occasions between 1330 and 1500 hours, and water temperature and pH measured with portable meters. Ponds were drained and fish were harvested from 17 to 19 October 2005 after 216–218 d in culture. The weights of the bluegills and grass carp in each pond were recorded. Data were analyzed by linear and nonlinear regression analyses using SigmaPlot (version 8.0) statistical software (SPSS 1997). Results and Discussion The average concentrations of total alkalinity and total hardness for individual ponds ranged from 37.3 to 48.2 mg/L and from 36.4 to 59.4 mg/L, respectively. These concentrations were within the recommended ranges for sport fish ponds in the southeastern United States (Boyd and Tucker 1998). All ponds received identical inputs of triple superphosphate, and total phosphorus concentrations averaged between 0.20 and 0.36 mg/L (Figure 1). Wudtisin and Boyd (2005) reported an average total phosphorus concentration of 0.18 mg/L for a pond fertilized at the P2O5 rate used in this study. Total nitrogen concentrations (Figure 1) increased with increasing ammonium nitrate application rates (r2 ¼ 0.70, P , 0.05). Average total ammonia-nitrogen concentrations were not correlated (P . 0.05) with nitrogen fertilizer application rate (Figure 1). This finding was not surprising because similar results have been observed in other pond fertilization experiments where water analyses were made several days after
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FIGURE 1.—Relationships between the amount of nitrogen per application and the concentrations of water quality variables in bluegill ponds. Fertilizers were applied at 3-week intervals. Ammonium nitrate was the nitrogen source, and ponds received 3 kg P2O5/ha from triple superphosphate on each fertilization date.
nitrogen fertilizer applications (Boyd and Tucker 1998) as was done in this study. Nevertheless, there was an immediate increase in the total ammonia-nitrogen concentration of about 0.05 mg/L for each kilogramper-hectare increase in the nitrogen rate after fertilizer application because ammonium nitrate dissolves quickly (Boyd 1981). Occasional afternoon measurements suggested that temperature usually was between 26 and 308C and pH was between 8.4 and 8.8 at a depth of 10 cm. Thus, the percentage un-ionized ammonia probably ranged from 10% to 35% during most afternoons (Boyd and Tucker 1998), and the concentration of unionized ammonia probably reached at least 0.25 mg/L
soon after fertilizer applications in the pond with the greatest nitrogen rate. Phytoplankton uptake, nitrification, and ammonia volatilization cause total ammonianitrogen concentrations to decline rather quickly (Gross et al. 2000). Nitrate-nitrogen concentrations increased (r2 ¼ 0.66, P , 0.05) as ammonium nitrate application rates increased (Figure 1). The chlorophyll-a concentration also increased with increasing fertilization rate up to 3 kg N/ha (r2 ¼ 0.53, P , 0.05) and remained essentially constant at higher nitrogen rates (Figure 1). The relationship was best described by a saturation model (Oliver and Yang 1988).
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FIGURE 2.—Relationships between the amount of nitrogen per application and bluegill production in ponds. Fertilizers were applied at 3-week intervals between 15 March and 25 September 2005. Ammonium nitrate was the nitrogen source, and ponds received 3 kg P2O5/ha from triple superphosphate on each fertilization date. The total bluegill production data were divided into two sets for the regression analysis (0–6 kg N/ha and 8–14 kg N/ha).
Ponds contained two distinct classes of fish at harvest. There were fish of 10 cm or more total length (TL) that comprised the initial stock. There were many smaller fish up to about 6 cm TL that resulted from reproduction by the initial stock. The total weight of the fish and the weight of the large fish were recorded for each pond, but fish were not counted. The total production of bluegills in ponds increased with increasing nitrogen input up to 18 kg ammonium nitrate/ha (6 kg N/ha) per application, but production declined at higher nitrogen rates (Table 1; Figure 2). In the phosphorus fertilization study of Wudtisin and Boyd (2005), bluegill production increased up to a phosphorus rate of 3 kg P2O5/ha and leveled off at higher rates. Production was between 501 and 558 kg/ ha at phosphorus rates of 3–8 P2O5/ha, and the data conformed to a saturation relationship. The regression line was fitted using a saturation model (Oliver and
Yang 1988). Bluegill production in the present experiment conformed to two relationships (Figure 2), a simple, positive linear one up to 6 kg N/ha (r2 ¼ 0.75, P , 0.05) and a simple, negative linear one at higher nitrogen rates (r2 ¼ 0.81, P , 0.05). Grass carp production was similar at all nitrogen application rates (Table 1). The harvest weight of the large fish was not correlated with the nitrogen fertilization rate (Figure 2), and there were no marked differences in the harvest weights of large fish among ponds (Table 1). The observed differences in total bluegill production with respect to nitrogen rate were related to differences in production of small fish at different nitrogen rates. Fish were not counted, but it was apparent that differences in production of small fish were the result of differences in number rather than size of fish. The chlorophyll-a concentration (Figure 1) suggests that the
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phytoplankton base of the food web reached a saturation level at the same nitrogen rate (6 kg N/ha) that led to maximum bluegill production (Figure 2). There was a positive correlation between chlorophyll-a concentration and total bluegill production for the nitrogen range of 0–6 kg N/ha (r2 ¼ 0.715, P , 0.05), but not over the entire nitrogen range of the study (r2 ¼ 0.145). None of the other measured water quality variables were correlated (P . 0.05) with bluegill production. However, the lower reproductive success at fertilization rates of 8 kg N/ha and above may have been related to the toxic effects of a high un-ionized ammonianitrogen concentration soon after fertilizer application on eggs, small fish, or natural food organisms in the ponds (Colt and Tchobanoglous 1978; Boyd and Tucker 1998). The phosphorus fertilizer rate of 3 kg P2O5/ha used in this study was established previously in ponds that had received phosphorus inputs in fertilizers and feeds for 31 years during which sediment had not been removed (Wudtisin and Boyd 2005). Sediment had been removed from ponds used in the present study, and Yuvanatemiya and Boyd (2006) found that phosphorus concentration in pond bottoms was greatly reduced. Nevertheless, there was no reason to expect that the ponds would have a greater need for phosphorus because of sediment removal. In ponds on the FRU that had received phosphorus inputs in feeds and fertilizers for 15–25 years, the sediment acted as a sink for rather than a source of phosphorus (Swingle et al. 1965; Masuda and Boyd 1994). Further evidence of 3 kg P2O5/ha being adequate in this study is the observation that the maximum total bluegill production of 552 kg/ha (Table 1) was similar to the value of 539 kg/ha achieved by Wudtisin and Boyd (2005) in ponds fertilized at this P2O5 rate. Moreover, total phosphorus concentration in pond waters of the current study were greater than that reported for a pond treated at 3 kg P2O5/ha by Wudtisin and Boyd (2005). The average concentrations of organic carbon and nitrogen in bottom soil samples from the 33-year-old E ponds were 1.22% and 0.14%, respectively, before sediment was removed. After sediment removal, the respective values declined to 0.99% and 0.10% (Yuvanatemiya and Boyd 2006). Renovated pond bottoms were higher in organic matter and nitrogen than the original bottoms of the E ponds, which contained 0.30% organic carbon and 0.07% total nitrogen (Munsiri et al. 1995). Nevertheless, the soil 5-d biochemical oxygen demand test (Xinglong and Boyd 2006) revealed that the microbial degradation rate of organic matter in bottom samples from ponds with intact sediment was about 10 times that in samples
from ponds from which sediment had been removed. Nitrogen mineralization also would be slow, and possibly not much greater than for the bottom soil of new ponds during the first crop. This study suggests that the optimum nitrogen application rate for new bluegill ponds or older ponds after sediment removal is about 6 kg N/ha. The N:P2O5 ratio for the optimum nitrogen application rate in this experiment was 2:1. It is fortuitous that the optimum phosphorus application rate of 3 kg P2O5 (1.3 kg P)/ha was determined in an experiment where twice as much N as P2O5 had been maintained across all treatments to assure adequate nitrogen (Wudtisin and Boyd 2005). The results of this study suggest that a fertilizer for new or renovated ponds should have an N:P2O5 ratio of 2:1 (N:P ¼ 4.6:1) instead of 1:1 (N:P ¼ 2.3:1), as often recommended. After a few years, sediment accumulates in pond bottoms and mineralization of organic matter provides sufficient inorganic nitrogen to sustain a high level of phytoplankton growth. Phosphorus-only fertilization with triple superphosphate (46% P2O5 [20% P]) is an option for older ponds. However, the modest amount of nitrogen provided by diammonium phosphate (18% N and 48% P2O5 [21% P]) may be beneficial in some older ponds (Boyd and Tucker 1998), and this fertilizer is not much more expensive than triple superphosphate. Based on the results presented above, we make the following fertilizer recommendations: (1) 6 kg N and 3 kg P2O5 (1.3 kg P)/ha per application for new ponds or old ponds from which sediment has been removed, and (2) 3 kg P2O5/ha from triple superphosphate or diammonium phosphate for ponds that have been fertilized for 5 years or more and from which sediment has not been removed. Fertilizer applications should usually be made at 3-week intervals. However, if a pond has a heavy phytoplankton bloom on the scheduled day, fertilization should be delayed. The results of this study should be most applicable to ponds situated on wooded watersheds in the Piedmont Plateau region of the southeastern United States. However, previous experience has shown that fertilizer procedures developed at the FRU can be applied to ponds in other regions (Boyd and Tucker 1998). References Boyd, C. E. 1981. Solubility of granular inorganic fertilizers for fish ponds. Transactions of the American Fisheries Society 110:451–454. Boyd, C. E. 1982. Hydrology of small experimental fish ponds at Auburn, Alabama. Transactions of the American Fisheries Society 111:638–644. Boyd, C. E. 1990. Water quality in ponds for aquaculture.
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Alabama Agricultural Experiment Station, Auburn University, Auburn. Boyd, C. E., and J. W. Sowles. 1978. Nitrogen fertilization of ponds. Transactions of the American Fisheries Society 107:737–741. Boyd, C. E., and C. S. Tucker. 1992. Water quality and pond soil analyses for aquaculture. Alabama Agricultural Experiment Station, Auburn University, Auburn. Boyd, C. E., and C. S. Tucker. 1998. Pond aquaculture water quality management. Kluwer Academic Publishers, Boston. Clesceri, L. S., A. E. Greenberg, and A. D. Eaton. 1998. Standard methods for the examination of water and wastewater, 20th edition. American Public Health Association, Washington, D.C. Colt, J., and G. Tchobanoglous. 1978. Chronic exposure of channel catfish, Ictalurus punctatus, to ammonia: effects on growth and survival. Aquaculture 15:353–372. Gross, A., and C. E. Boyd. 1998. A digestion procedure for the simultaneous determination of total nitrogen and total phosphorus in pond water. Journal of the World Aquaculture Society 29:300–303. Gross, A., C. E. Boyd, and C. W. Wood. 2000. Nitrogen transformation and balance in channel catfish ponds. Aquacultural Engineering 24:1–14. Masuda, K., and C. E. Boyd. 1994. Phosphorus fractions in soil and water of aquaculture ponds built on clayey Ultisols at Auburn, Alabama. Journal of the World Aquaculture Society 25:379–395. McNutt, R. B. 1981. Soil survey of Lee County, Alabama. U.S. Government Printing Office, Washington, D.C. Metzger, R. J., and C. E. Boyd. 1980. Liquid ammonium polyphosphate as a fish pond fertilizer. Transactions of the American Fisheries Society 109:563–570.
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Munsiri, P., C. E. Boyd, and B. J. Hajek. 1995. Physical and chemical characteristics of bottom soil profiles in ponds at Auburn, Alabama, USA, and a proposed method for describing pond soil horizons. Journal of the World Aquaculture Society 26:346–377. Murad, A., and C. E. Boyd. 1987. Experiments on fertilization of sport fish ponds. Progressive Fish-Culturist 49:100– 107. Oliver, R. M., and H. J. Yang. 1988. Saturation models: a brief survey and critique. Journal of Forecasting 7:215– 223. SPSS. 1997. SigmaPlot, version 8.0. SPSS, Chicago. Swingle, H. S. 1947. Experiments on pond fertilization. Alabama Agricultural Experiment Station Bulletin (Auburn University) 264. Swingle, H. S., B. C. Gooch, and H. R. Rabanal. 1965. Phosphate fertilization of ponds. Proceedings of the Annual Conference Southeastern Association of Game and Fish Commissioners 17(1963):213–218. van Rijn, J. 1993. Methods to evaluate water quality in aquaculture. Hebrew University of Jerusalem, Rehovot, Israel. Wudtisin, W., and C. E. Boyd. 2005. Determination of the phosphorus fertilization rate for bluegill ponds using regression analysis. Aquaculture Research 36:593–599. Xinglong, J., and C. E. Boyd. 2006. Relationship between organic carbon concentration and potential pond bottom soil respiration. Aquacultural Engineering 35:147–151. Yuvanatemiya, V., and C. E. Boyd. 2006. Physical and chemical changes in aquaculture and bottom soil resulting from sediment removal. Aquacultural Engineering 35:199–205.
