Dewatering Aquaculture Effluent For The Hydroponic Production of Pak Choi (Brassica rapa chinensis) and Production of Vegetable Seedlings

Final Report for GS11-098

Project Type: Graduate Student
Funds awarded in 2011: $9,932.00
Projected End Date: 12/31/2013
Grant Recipient: Auburn University
Region: Southern
State: Alabama
Graduate Student:
Major Professor:
Dr. Jesse Chappell
Auburn University
Expand All

Project Information

Summary:

The aquaculture industry will continue to grow in order to meet the consumer’s demand for aquatic animal protein. Recirculating aquaculture systems will help to intensify production on the producer’s farm, but waste water treatment technologies will be required to ensure the discharged waste does not have a socio-economic impact on limited, natural resources. Geotextile technology aides in the capture and treatment of discharged wastes on the producer’s farm, but finding ways to utilize the solid and liquid component created by the geotextile technology will be required. Using the solid and liquid components for horticulture plant production may provide farmers with a method for additional on-site waste remediation while diversifying production. The experimental trials using the solid component suggest incorporating low levels of dewatered aquaculture effluent into commercial substrates may provide a means of redirecting aquaculture waste into a resource for horticulture production. The plant growth response was dependent on the substrate and water source. The benefits of the leachate exiting the geotextile bag were dependent on the source of aquaculture effluent and the management of the production system. Nonetheless, the high pH level of the leachate will need to be managed to ensure optimal levels are maintained for plant production. Acid injection is commonly used by the horticulture industry to mitigate sub-optimal pH of irrigation water. Appropriate choice of acid and its injection could provide supplemental nutrients and lower pH in circumstances where the leachate exiting the geotextile bag is deficient in dissolved macronutrients. The cost associated with acid injection will be dependent on the chemical parameters of leachate (i.e. alkalinity). Using the leachate as a plant nutrient source will be important in regions where quantities of commercial, inorganic fertilizers are difficult to obtain and freshwater resources are depleted.

Introduction

The aquaculture industry will continue to grow in order to meet the consumer’s demand for aquatic animal protein. Recirculating aquaculture systems will help to intensify production on the producer’s farm, but waste water treatment technologies will be required to ensure the discharged waste does not have a socio-economic impact on limited, natural resources. Geotextile technology aides in the capture and treatment of discharged wastes on the producer’s farm, but finding ways to utilize the solid and liquid component created by the geotextile technology will be required. Using the solid and liquid components for horticulture plant production may provide farmers with a method for additional on-site waste remediation while diversifying production. The experimental trials using the solid component suggest incorporating low levels of dewatered aquaculture effluent into commercial substrates may provide a means of redirecting aquaculture waste into a resource for horticulture production. The plant growth response was dependent on the substrate and water source. The benefits of the leachate exiting the geotextile bag were dependent on the source of aquaculture effluent and the management of the production system. Nonetheless, the high pH level of the leachate will need to be managed to ensure optimal levels are maintained for plant production. Acid injection is commonly used by the horticulture industry to mitigate sub-optimal pH of irrigation water. Appropriate choice of acid and its injection could provide supplemental nutrients and lower pH in circumstances where the leachate exiting the geotextile bag is deficient in dissolved macronutrients. The cost associated with acid injection will be dependent on the chemical parameters of leachate (i.e. alkalinity). Using the leachate as a plant nutrient source will be important in regions where quantities of commercial, inorganic fertilizers are difficult to obtain and freshwater resources are depleted.

Project Objectives:

The objectives of the proposed project were: 1) Use filtrate exiting the geotextile bag as a nutrient source for a cultivar trial of hydroponically produced pak choi at Auburn University and evaluate plant growth parameters and health. 2) Repeat objective one with the two best pak-choi cultivars at a moderate-sized aquaculture farm utilizing RAS technology in Browns, Alabama and evaluate plant growth parameters and health. 3) Evaluate the dewatered solids as an element of soilless media and nutrient source for the production of vegetable seedlings. Plant growth parameters and health of transplants were assessed.

Cooperators

Click linked name(s) to expand
  • Dr. Jesse Chappell
  • Jason Danaher

Research

Materials and methods:

Objective 1 The geotextile leachate used in this experiment was collected from a 100-m3 intensive, freshwater RAS producing Nile tilapia. Fish were stocked at 40 fish/m3 and fed an extruded diet containing 36% protein. A 4.6 m × 3.1 m woven geotextile bag (U.S. Fabrics, Inc., Cincinnati, Ohio) was installed adjacent to the fish facility and housed in a 6.1 × 2.4 m roll-off dumpster pitched at approximately a 1% grade. The dumpster was covered to prevent rainfall from diluting leachate. On a daily basis, effluent discharged from the filtration units was injected with HaloKlear™ LiquiFloc 1% (HaloSource Inc., Bothell, Washington), a chitosan based biopolymer, at 1 to 3 mg/L active ingredient before entering the geotextile bag. Leachate exiting the geotextile bag was collected in a 378 liter sump. The leachate was sent to an adjacent 29.3 × 9.1 m double polyethylene covered greenhouse where the plant experiment was conducted. In the plant greenhouse an ebb and flow system was constructed from an 2.4 m x 0.9 m rectangular, fiberglass tank filled with 10.2 cm of Hydrock substrate. A bell siphon was installed to allow the ebb and flow system to fill and drain. A 208 liter plastic drum acted as the sump for leachate storage and a 1/3 Hp submersible pump flooded the system over a four minute period. A digital timer was used to turn the submersible pump on and off for the four minute time period. The pump flooded the system twelve times daily from transplanting seedlings until harvest. Leachate was totally replaced every seven days. The initial chemical parameters of the leachate were analyzed for dissolved nutrient content and the pH of the leachate was adjusted daily using citric acid to maintain a pH of 6.0 – 6.5. Four varities of pak choi were evaluated. Two were dwarf varieties (white stem hybrid dwarf and white small dwarf) and two were standard varieties (green and white) (Kitazawa Seed Co., Oakland CA). Seeds were germinated in 2.54 cm thin cut Oasis® Horticubes® (Smithers–Oasis Company, Kent, OH). On 4 March 2013 a single, four-week-old seedling was transplanted into the ebb and flow system. To ensure roots of individual plants did not compete for space each seedling was placed into a 473 cm-3 square (9.84×8.57 cm) plastic pot (Dillen™ Products, Middlefield, OH). The plastic pot contained Hydrock substrate and was buried in the remaining Hydrock substrate in the ebb and flow system. Holes present from the manufacturing process allowed leachate to enter and drain from each pot during each flooding event. Seedlings were spaced 20.3 cm on centers. The experiment was a completely randomized design with 9 single-pot replications per variety. A t?test was used to compare plant growth (P ≤ 0.05) among the dwarf and standard varieties. A destructive harvest was performed 18 DAP. Leaf greenness was recorded using a chlorophyll meter (SPAD-502; Minolta Camera Company, Ramsey, NJ) and taking the average reading of 3 leaves per plant. Plant height was measured from the substrate surface to the highest point of each plant. All plants were measured for growth index (GI) = [(height + width + perpendicular width) ÷3] at harvest. Shoot dry matter, root dry matter and total plant dry matter were quantified by drying plant parts in a forced air oven set at 70oC for 72 hr. The shoot to root ratio was calculated, as well. Objective 2 The farm in Browns, AL discharged effluent daily from its mechanical filters and the discharged effluent was sent to a holding pond adjacent to the facility. Effluent for the experiment was collected from a concrete sump that was placed in line with the plumbing used to transport discharge effluent from the production facility to the holding pond. Approximately 360 liters of discharged aquaculture effluent was collected from the farm in Browns, AL and brought back to Auburn, AL. Two trips were made to the farm over a fourteen day period to get discharged effluent. The experiment was performed in a double layer, polyethylene covered greenhouse at the E.W. Shell Fisheries Center, North Auburn Unit, in Auburn, Alabama, from 7 August to 23 August 2013. In the greenhouse a 2 m × 1 m, non-woven geotextile bag was installed on approximately a 1% grade. The discharged effluent was injected with HaloKlear™ LiquiFloc 1% (HaloSource Inc., Bothell, Washington), a chitosan based biopolymer, at 1 to 3 mg/L active ingredient before entering the geotextile bag. Leachate exiting the geotextile bag was collected in a 380 liter sump. Two varieties of pak choi were evaluated separately: 1) White small dwarf and 2) White standard (Kitazawa Seed Co., Oakland CA). The experiment was a completely randomized design with 10 single-pot replications per treatment. Treatment one used leachate from the geotextile bag and the second treatment used 100 mg?L-1 nitrogen with Total Gro™ water soluble 20-4.4-16.6 N-P-K fertilizer (SDT Industries, Inc., Winnsboro, LA). The inorganic fertilizer was mixed in a 175 liter plastic tub to create a stock solution. The geotextile leachate in the catchment sump was mixed thoroughly before it was distributed to the growing pots. The 30 cm square, polystyrene sheet rested on a 3.78 liter plastic pot containing either nutrient solution. A regenerative blower delivered air through a 2.54 cm PVC distribution line. A single 2.5 cm airstone was placed into each pot to deliver air to the root zone and mix the nutrient solution. All pots were on a raised bench. Chemical parameters of the geotextile leachate were evaluated prior to being distributed to each pot. A destructive harvest was done 16 DAP. Leaf greenness was recorded using a chlorophyll meter (SPAD-502; Minolta Camera Company, Ramsey, NJ) and taking the average reading of 3 leaves per plant. Plant height was measured from the surface of the polystyrene board to the highest point of each plant. All plants were measured for growth index (GI) = [(height + width + perpendicular width) ÷3] at harvest. Shoot dry matter were quantified by drying in a forced air oven set at 70oC for 72 hr. Objective 3 The dewatered aquaculture effluent (AE) used in all experiments was collected from a 100-m3 intensive, freshwater RAS producing Nile tilapia. Fish were stocked at 40 fish/m3 and fed an extruded diet containing 36% protein. A 4.6 m × 3.1 m woven geotextile bag (U.S. Fabrics, Inc., Cincinnati, Ohio) was installed adjacent to the fish facility and covered to prevent rainfall from diluting leachate. Effluent discharged from the filtration units was injected with HaloKlear™ LiquiFloc 1% (HaloSource Inc., Bothell, Washington), a chitosan based biopolymer, at 1 to 3 mg/L active ingredient. After repeated fillings the bag was allowed to dewater and cut open to remove the solids. Solids were allowed to air-dry and then further processed with a hammer mill (Model 30; C.S. Bell Co., Tiffin, Ohio) to pass through 0.635-cm screen. Afterwards, Fafard 3B mix (F3B) (Conrad Fafard, Inc., Agawam, MA) was replaced with different amounts of AE by mixing components together in a cement mixer for 3 minutes. Tomato Experiments Experiment 1 was performed in a gutter connected, twin-wall polycarbonate greenhouse at the Paterson Greenhouse Complex, Auburn University, Auburn, Alabama, from 21 March to 4 April 2012. The experiment was a completely randomized design with 17 single-pot replications per treatment. Treatments were: 1) 100% F3B (control); 2) 25% AE; 3) 50% AE; and 4) 75% AE. Experiment 2 was performed in a double layer, polyethylene covered greenhouse at the E.W. Shell Fisheries Center, North Auburn Unit, in Auburn, Alabama, from 5 to 26 June 2012. The experiment was a completely randomized design with 14 single-pot replications per treatment. Treatments were: 1) 100% F3B (control); 2) 5% AE; 3) 10% AE; 4) 15% AE; and 5) 20% AE. For both experiments tomato seed were germinated in 2.54 cm thin cut Oasis® Horticubes® (Smithers–Oasis Company, Kent, OH). For Experiment 1 a single, uniform seedling was potted 17 days after sowing, when the first true leaves developed, into each 473 cm-3 square (9.84×8.57 cm) plastic pot (Dillen™ Products, Middlefield, OH) containing substrates. In Experiment 2 a single seedling was potted 13 days after sowing into the same size pots used in the first experiment, when the first true leaves developed. All pots were placed on raised benches and for the first week only municipal water was applied using a shower wand and hose. Thereafter, pots were hand watered daily with municipal water and were fertigated twice weekly (Tuesday and Thursday) using a Dosatron® (Dosatron International, Inc., Clearwater, FL) injector at 100 mg?L-1 nitrogen with Total Gro™ water soluble 20-4.4-16.6 N-P-K fertilizer (SDT Industries, Inc., Winnsboro, LA). Pots were watered until substrate reached saturation, i.e., until water leached from the bottom of the pot. Physical and chemical parameters of substrates were analyzed. A destructive harvest was performed 14 DAP in Experiment 1 and 21 DAP in Experiment 2 to quantify plant growth parameters. Plant height was measured from the substrate surface to the tip of the seedling. Leaf area was measured by passing all green leaves from each replicate through a LI-COR 3000 leaf area meter (LI-COR, Lincoln, NE). Stem dry matter, leaf dry matter, and total plant dry matter were quantified by drying plant parts in a forced air oven set at 70oC for 72 hr. The total dry matter included cotyledons. Data were analyzed with SPSS (ver. 16.0; IBM Corp., Armonk, NY) and tested for normality using the Shapiro-Wilk test. One-way analysis of variance (ANOVA) was used to determine effects of substrate on physical and chemical parameters and tomato seedling growth parameters. Specific post-hoc comparisons between the control and other treatments were used for plant growth parameters at harvest using Dunnett’s two tailed t-test. Pepper Experiment The experiment was performed in a double layer, polyethylene covered greenhouse at the E.W. Shell Fisheries Center, North Auburn Unit, in Auburn, Alabama, from 30 March to 26 April 2013. The trial was designed as a 5 × 2 factorial evaluating five substrates and two water sources (water soluble, inorganic fertilizer or municipal water). The experiment was a completely randomized design with 10 single-pot replications per treatment. Treatments were: 1) 100% F3B (control); 2) 10% AE; 3) 25% AE; 4) 50% AE; and 5) 75% AE. Capsicum annum ‘Ace’ seeds were germinated in 2.54 cm thin cut Oasis® Horticubes® (Smithers–Oasis Company, Kent, OH) and a single, four-week-old uniform seedling was potted into each 473 cm-3 square (9.84×8.57 cm) plastic pot (Dillen™ Products, Middlefield, OH) containing substrates. All pots were placed on raised benches and for the first week only municipal water was applied using a shower wand and hose. Thereafter, pots were hand watered daily, based on treatment. Treatments receiving fertigation were watered twice weekly (Tuesday and Thursday) using a Dosatron® (Dosatron International, Inc., Clearwater, FL) injector at 100 mg?L-1 nitrogen with Total Gro™ water soluble 20-4.4-16.6 N-P-K fertilizer (SDT Industries, Inc., Winnsboro, LA). Pots were watered until substrate reached saturation, i.e., until water leached from the bottom of the pot. Physical and chemical parameters of substrates were analyzed. A destructive harvest was performed 26 DAP plant growth parameters. Leaf greenness was recorded using a chlorophyll meter (SPAD-502; Minolta Camera Company, Ramsey, NJ) and taking the average reading of 3 leaves per plant. Plant height was measured from the substrate surface to the tip of the seedling. Stem dry matter, leaf dry matter, and total plant dry matter were quantified by drying plant parts in a forced air oven set at 70oC for 72 hr. Two–way analysis of variance (ANOVA) was used to determine the main effect of substrate and water on pepper plant growth. If a significant interaction existed (P ≤ 0.05), pairwise comparisons on the individual group means within each simple effect were conducted and means were separated using the Bonferroni adjusted α-level (P ≤ 0.05). If no significant (P > 0.05) statistical interaction was identified, the main effects of substrate and water were analyzed separately and means were separated by Tukey’s test (P ≤ 0.05). Pak Choi Experiment The experiment was performed in a double layer, polyethylene covered greenhouse at the E.W. Shell Fisheries Center, North Auburn Unit, in Auburn, Alabama, from 30 March to 26 April 2013. The trial was designed as a 5 × 2 factorial evaluating five substrates and two water sources (water soluble, inorganic fertilizer or municipal water). The experiment was a completely randomized design with 12 single-pot replications per treatment. Treatments were: 1) 100% F3B (control); 2) 10% AE; 3) 25% AE; 4) 50% AE; and 5) 75% AE. A white standard variety of pak choi was used (Kitazawa Seed Co., Oakland CA). Seeds were germinated in 2.54 cm thin cut Oasis® Horticubes® (Smithers–Oasis Company, Kent, OH) and a single, four-week-old uniform seedling was potted into each 473 cm-3 square (9.84×8.57 cm) plastic pot (Dillen™ Products, Middlefield, OH) containing substrates. All pots were placed on raised benches and for the first week only municipal water was applied using a shower wand and hose. Thereafter, pots were hand watered daily, based on treatment. Treatments receiving fertigation were watered twice weekly (Tuesday and Thursday) using a Dosatron® (Dosatron International, Inc., Clearwater, FL) injector at 100 mg?L-1 nitrogen with Total Gro™ water soluble 20-4.4-16.6 N-P-K fertilizer (SDT Industries, Inc., Winnsboro, LA). Pots were watered until substrate reached saturation, i.e., until water leached from the bottom of the pot. Physical and chemical parameters of substrates were analyzed. A destructive harvest was performed 16 DAP. Leaf greenness was recorded using a chlorophyll meter (SPAD-502; Minolta Camera Company, Ramsey, NJ) and taking the average reading of 3 leaves per plant. Plant height was measured from the substrate surface to the tip of the seedling. All plants were measured for growth index (GI) = [(height + width + perpendicular width) ÷3] at harvest. Total plant dry matter was quantified by drying plant parts in a forced air oven set at 70oC for 72 hr. Two–way analysis of variance (ANOVA) was used to determine the main effect of substrate and water on pepper plant growth. If a significant interaction existed (P ≤ 0.05), pairwise comparisons on the individual group means within each simple effect were conducted and means were separated using the Bonferroni adjusted α-level (P ≤ 0.05). If no significant (P > 0.05) statistical interaction was identified, the main effects of substrate and water were analyzed separately and means were separated by Tukey’s test (P ≤ 0.05).

Research results and discussion:

Objective 1 The initial pH of the leachate exiting the geotextile bag was high for hydroponic plant production (Table 1). Anaerobic conditions in the bag resulted in the net production of alkalinity. The addition of citric acid brought the pH down to acceptable levels of 6.0 to 6.5, but the daily addition of citric acid was necessary to maintain pH within this range. We hypothesize the hydrock substrate contained some residual source of alkalinity, therefore increasing pH levels throughout the day. As a result, hydrock may not be the best source of substrate for ebb and flow aquaponics systems and alternative inorganic substrates should be evaluated. No differences in plant growth parameters were observed among the dwarf varieties tested (Table 2). The SPAD readings were different among the dwarf varieties, but visual appearance probably would not have affected marketing the final product. The plant height and growth index for the standard green variety was reduced compared to the standard white. Other growth parameters were similar between the two standard varieties. In general, all varieties responded well to the nutrient concentrations available in the geotextile bag leachate. Plant tissue analysis suggests the leachate from the E.W. Shell Fisheries RAS had sufficient quantities of available nutrients for plant growth (Table 3). This study suggests the leachate exiting a geotextile bag dewatering discharged aquaculture effluent could supply adequate nutrients for leafy green production, but acid addition would be necessary to create optimal pH for the nutrient solution. The discharged waste could be thought of as a potential resource for aquaculture producers wishing to diversify their production system. Objective 2 Both varities of pak choi responded better to the commercial, inorganic fertilizer as a nutrient source rather than the leachate exiting the geotextile bag (Table 4). The leachate lacked adequate nitrogen concentrations for vigorous plant growth and the pH of the leachate was not optimal for hydroponic crops (Table 5). Plant growth response in the first trial conducted using effluent from the system at the E.W. Shell Fisheries Station was substantially different in nutrient content. This may reflect the difference between the two production systems and their management. The system at the E.W. Shell Fisheries Station only required a 1?2% water exchange per day based on its volume and therefore nutrients were more concentrated for plant growth. The RAS in Browns, Alabama required 5-10% water exchange per day based on volume. Also, the filtration methods were different among fish systems. The system at Browns, Alabama required more water to properly flush the mechanical filters; therefore, diluting the dissolved nutrients and solid concentration discharged (0.5% solids content). The system at the E.W. Shell Fisheries Station produced a more concentrated dissolved and organic waste (1.5 to 2.0% solids content). To overcome the diluted nutrient concentration we would recommend the farmer utilize leachate exiting the geotextile bag after prolonged accumulation of solids in the bag. The geotextile bag is capable of capturing the organic matter in fish effluent and preventing it from escaping the bag; however, dissolved nutrients leach from the bag overtime. Mineralization of the solid matter results in the release of dissolved macronutrients over time. Installing a geotextile bag and operating it for several months prior to integrating facilities for hydroponic production may improve dissolved nutrient concentration for plant production. Acid injection into the leachate from the Browns, Alabama system may also help make nutrients more available for plant uptake. Injection of nitric acid or phosphoric acid may provide a means of lowering leachate pH and supplement dissolved nutrient concentrations. Citric acid was used in the first experimental trials at the E.W. Shells Fisheries station as a method of lowering pH without supplementing nutrient concentrations; however, on a commercial scale system citric acid would be the most expensive means to create an optimal pH level compared to other commonly used acids to reduce pH of irrigation water for horticulture plant production. Because the hydroponic infrastructure at the farmer’s production facility was undergoing construction the economics could not be evaluated as originally intended. However, a simple economic analysis was done during trials at the E.W. Shell Fisheries Station to determine the cost of obtaining the solid and liquid component created by the geotextile bag and polymer. It was based on five-month production period of Nile tilapia produced in the 100 m3 biofloc system at the E.W. Shell Fisheries Center, North Auburn Unit, in Auburn, AL. The cost of the 4.6 × 3.1 m, 10 oz, non-woven geotextile bag was $171 and two, 19 liter buckets of liquifloc 1% chitosan ($102 per bucket) were required to flocculate the discharged effluent. The total cost of materials was $375. The total volume of discharged effluent entering the geotextile bag was 36,495 liters and the total volume of leachate captured was 32,945 liters. Therefore, we were able to treat and recapture approximately 90% of the original waste volume for potential plant production at the cost of $0.01 per liter of leachate. A total of 1,505 kg of diet (dry weight) was fed to the system over the five-month production period and approximately 284 kg of solids (dry weight), or 19% of the diet fed, was captured in the geotextile bag. This equates to $1.32 per kg for dewatered solid matter (dry weight). In the first pak choi variety trial performed at the E.W. Shell Fisheries Station the leachate required approximately 0.5 g/L of citric acid daily to maintain a nutrient solution of 6.0 to 6.5. A 22.7 kg bucket of citric acid cost $3.74/kg. This equates to a cost of approximately $0.19 per 100 liters of leachate daily. Therefore, the material cost to create the leachate and the chemical cost to treat 100 liters of leachate for a seven day period was $2.33. The commercial inorganic fertilizer cost was $3.15 per kg. To create a 100 ppm nitrogen nutrient solution would cost $0.16 per 100 liters. This results in a fourteen to fifteen fold cost increase to use leachate compared to the inorganic fertilizer. For this reason we would suggest using an alternative acid to lower leachate pH for hydroponic plant production. In addition, using the Hydrock substrate for plant production may not be viable if residual sources of alkalinity are present in the media. An alternative substrate for an ebb and flow system or a raft system may provide a more economical approach to reduce the amount of citric acid required to maintain optimal pH for hydroponic plant production. Objective 3 Tomato Experiment 1 Physical properties of substrates differed due to treatment (Table 6). Increased AE decreased total porosity and air space, increased bulk density, and did not affect container capacity. The total porosity for 50 and 75% AE amended substrates was reduced by 6.3 and 5.4%, respectively, compared to the control. The air space for 50 and 75% AE was lowered by 55.4 and 37.1%. Differences in total porosity, airspace, and bulk density of substrates compared to the control can likely be explained by the texture of each substrate (Table 7). As percent of AE increased, percent of coarse particles decreased and medium-sized particles increased and fine-sized were not affected in the final substrate. Redistribution of particle size decreased percent of air space in substrates and increased bulk density. Inclusion of ≥25% AE reduced particle size while ≥50% AE impacted substrate physical properties. This impact on air space may have inhibited plant growth by limiting oxygen concentration and exchange within the container substrate. Initial chemical properties of F3B and AE are presented in Table 8. Increased proportions of AE increased substrate leachate pH of all amended substrates. The rise in pH was greater as proportion of AE increased (Table 9). Substrate leachate pH 3, 8, and 13 DAP for all AE amended substrates was greater than the control and exceeded recommended ranges of 5.5 to 7.0 suggested by Gorbe and Calatayud (2010) and Herrera et al. (2008). Increased proportions of AE resulted in elevated substrate leachate EC (Table 9) since initial chemical properties of AE had greater EC than F3B (Table 8). On all sampling dates substrate leachate EC from AE amended substrates was greater than the control. The relationship between increasing AE amount and increasing leachate EC may be due to continued breakdown and release of soluble salts. Smaller particle size, with increasing amounts of AE (Table 7), may have expedited leaching through physical breakdown of substrate components. Wright (1986) reported substrate leachate EC values <3.5 mS?cm-1 are required for healthy seedling growth. The control and 25% AE were the only substrates with this range of EC. Compared to the control, EC of substrate leachate for 25, 50, and 75% AE increased 4.2, 5.2, and 7.8 times, respectively, by 13 DAP. Elevated pH and EC with increased proportions of AE likely impacted final plant growth parameters. Plant growth parameters were greater for the control than all other treatments (Table 10). Compared to the control, plant height, leaf area, leaf dry matter, stem dry matter, and total dry matter were reduced 29 to 74%, 50 to 96%, 55 to 97%, 53 to 94%, and 52 to 94%, respectively, for treatments with 25 to 75% replacement of F3B with AE. Atiyeh et al. (2000) and Herrera et al. (2008) reported replacement of commercial substrates with up to 30% (v/v) vermicompost, or municipal solid waste, respectively, improved tomato seedling growth while greater amounts decreased plant growth. Herrera et al. (2008) concluded reduced proportions of municipal solid improved plant quality through reduced incidence of high pH and EC. Nonetheless, Lazcano et al. (2009) and Danaher et al. (2011) found amendments of ≥50% (v/v) vermicompost and composted aquaculture effluent, respectively, improved tomato seedling growth. Jahromi et al. (2012) found tomato seedlings grown with 60 and 100% compost derived from garden waste and cow manure performed better than a peat-based control even though EC exceeded 3.5 mS?cm-1. This may indicate the optimum ratios with respect to physical and chemical properties of each substrate affected final plant growth at harvest. Organic substrates vary in physical and chemical properties and each must be evaluated as a substrate amendment. Physical and chemical parameters of animal wastes and municipal solid waste may be inconsistent between animal species and between consecutive batches, even at the same operation (Garcia-Delgado et al., 2007; Naylor et al., 1999). It is necessary that physical and chemical properties of these composts be evaluated before and after partially replacing traditional substrates. Tomato Experiment 2 Total porosity of 10% AE was reduced by 4% compared to the control. All other substrates had similar total porosity compared to the control (Table 6). There were no differences in container capacity or air space among substrates. Inclusion of ≥5% AE (by volume) increased bulk density compared to the control. Similar to Experiment 1, increased percentages of AE within the substrate decreased amounts of coarse-sized particles and increased percent of medium-size particles and fine-size particles were not affected (Table 7). Melgar-Ramirez and Pascual-Alex (2010) and Hicklenton et al. (2001) reported substrate physical property qualities decreased as increased levels of compost were amended into the original substrate. Physical parameters of the present experiment remained within suggested ranges (Yeager et al., 2007). Substrate leachate pH 3, 10, and 17 DAP for AE amended substrates was greater than the control with exception of 10% AE at 17 DAP (Table 9). Even though there was a difference among substrates, pH for ≤15% AE substrates reached optimal ranges by 10 DAP. Tyler et al. (1993) and Marble et al. (2010) reported increased substrate pH with increased concentrations of composted poultry litter added to container substrate. Melgar-Ramirez and Pascual-Alex (2010) observed increased pH of substrate with greater amounts of vermicompost indicating some treated forms of animal wastes make the substrate more alkaline. Substrates with ≥10% AE resulted in increased substrate leachate EC values (Table 9). Substrate leachate EC for ≤15% AE were in the range reported by Wright (1986) at 3 DAP. Substrates with ≥10% AE had greater EC than the control up to 17 DAP, while 5% AE differed from the control only at 10 DAP. The pH and EC quickly reached optimal ranges, and the values agree with Herrera et al. (2008) that decreased proportions of alternative substrate components can improve plant quality through reduced incidence of high pH and EC. Seedlings grown with 5% AE had increased plant height, leaf area, leaf dry matter, stem dry matter, and total dry matter of 26, 124, 87, 75, and 83%, respectively, compared to the control (Table 10). Atiyeh et al. (2001) and Subler et al. (1998) reported incorporation of 5 and 10%, respectively, vermicompost (v/v) into a commercial container substrate increased total biomass of tomato seedlings at harvest. Seedlings grown in 5% AE may have benefited more from improved microbial activity in the substrate (Atiyeh et al., 2001) than additional nutrients present in the AE (Table 8) as suggested by Atiyeh et al. (2000) and Theunisson et al. (2010). Only seedling height and leaf area were improved with 10 and 15% AE (Table 9). Plant tissue analysis was not analyzed, but may have been helpful in determining why growth responses were different. Atiyeh et al. (2000) found when all required mineral nutrients were supplied commercially available potting substrate amended with 10 to 20% vermicomposted pig solids enhanced growth of tomato seedlings compared to commercial mix alone. Experiment 2 reflects findings of Atiyeh et al. (2000) and even further reductions of AE improved plant growth. However, leaf area, leaf dry matter, stem dry matter, and total dry matter of seedlings grown with 20% AE decreased 41, 72, 62, and 69%, respectively, compared to the control. Combined effects of elevated EC (>3.5 mS?cm-1) up to 10 DAP and pH >7.0 was detrimental to seedlings grown in 20% AE. The physical and chemical properties of substrate were improved by mixing AE at rates <20% container volume. Partial substitution of commercially available potting substrate with AE for tomato, cv. Bolseno, seedling production improved plant growth and quality if used at ≤15% the mixture. Alternative tomato cultivars tolerant to increased salinity (Al-Harbi et al., 2008) could be evaluated when AE is used to replace commercial potting mix. Application of AE to soil needs to be compared to other animal wastes to determine effects on fruit quality of vegetable crops with increased tolerance to dissolved salts. These results may provide a potential waste management strategy for the aquaculture industry, and a resource for the horticulture industry. Pepper Outcome Physical properties of substrates differed among substrates. Increased AE decreased total porosity and air space, increased bulk density, but did not affect container capacity. The initial pH of substrates tended to increase with greater amounts of AE, but by harvest only 50% AE remained at suboptimal levels (Table 11). The initial EC of substrates increased as greater amounts of AE was incorporated into the substrate and remained greater for the duration of the experiment. At harvest water source did not affect plant height; however, plants grown in ≥ 25% AE had reduced plant height (Table 12). There was a substrate and water interaction that affected remaining plant growth parameters at harvest. Water source did not affect plant growth when pepper plants were grown in 10% AE indicating this substrate provided sufficient nutrients to produce pepper transplants and provided adequate physical and chemical parameters, as well. These results may provide a potential waste management strategy for the aquaculture industry, and a resource for the horticulture industry. Pak choi Outcome Physical properties of substrates differed among substrates. Increased AE decreased total porosity and air space, increased bulk density, but did not affect container capacity. The effect of substrate decreased plant growth as greater amounts of AE were incorporated into the container substrate. The effect of substrate on air space may have inhibited plant growth by limiting oxygen concentration and exchange within the container substrate. Also, increased soluble salt concentrations with greater amounts of AE could have reduced plant growth (Table 13). There was no interaction effect of substrate and water on plant growth parameters (Table 14). Pak choi responded better to substrates with ≤ 10% AE and performed better when fertigation was applied rather than just municipal water. Integrated fish farms could partially replace commercial potting mix with low levels of dewatered aquaculture effluent to produce pak choi seedlings for their aquaponics facility. References Adler, P.R., S.T. Summerfelt, D.M. Glenn, and F. Takeda. 2003. Mechanistic approach to phytoremediation of water. Ecol. Eng. 20: 251-264. Al-Harbi, A.R., M.A. Wahb-Allah, and S.S. Abu-Muriefah. 2008. Salinity and nitrogen level affects germination, emergence, and seedling growth of tomato. Int. J. Veg. Sci. 14: 380-392. Arenas, M., C.S. Vavrina, J.A. Cornell, E.A. Hanlon, and G.J. Hochmuth. 2002. Coir as an alternative to peat in media for tomato transplant production. HortScience 37: 309-312. Atiyeh, R.M., S. Subler, C.A. Edwards, G. Bachman, J.D. Metzger, and W. Shuster. 2000. Effects of vermicomposts and composts on plant growth in horticultural container media and soil. Pedobiologia 44: 579-590. Atiyeh, R.M., C.A. Edwards, S. Subler, and J.D. Metzger. 2001. Pig manure vermicompost as a component of a horticultural bedding plant medium: effects on physicochemical properties and plant growth. Bioresour. Technol. 78: 11-20. Azim, M.E. and D.C. Little. 2008. The biofloc technology (BFT) in indoor tanks: Water quality, biofloc composition, and growth and welfare of Nile tilapia (Oreochromis niloticus). Aquaculture 283: 29-35. Bachman, G.R. and J.D. Metzger. 2008. Growth of bedding plants in commercial potting substrate amended with vermicompost. Bioresour. Technol. 99: 3155-3161. Bilderback, T.F., W.C. Fonteno, and D.R. Johnson. 1982. Physical properties of media composed of peanut hulls, pine bark and peat moss and their effects on azalea growth. J. Amer. Soc. Hort. Sci. 107: 522-525. Boyd, C.E. and C.S. Tucker. 1998. Pond aquaculture water quality management. Kluwer Academic Publishers, Boston, MA. Ceglie, F.G., H. Elshafie, V. Verrastro, and F. Tittarelli. 2011. Evaluation of olive pomace and green waste composts as peat substitutes for organic tomato seedling production. Compost Sci. Util. 19: 293-300. Danaher, J.J., E. Pantanella, J.E. Rakocy, R.C. Shultz, and D.S. Bailey. 2011. Dewatering and composting aquaculture waste as a growing medium in the nursery production of tomato plants. Acta Hort. 891: 223–229. Ebeling, J.M., K.L. Rishel, and P.L. Sibrell. 2005. Screening and evaluation of polymers as flocculation aids for the treatment of aquacultural effluents. Aquacult. Eng. 33: 235-249. Evans, M.R. and M. Gachukia. 2004. Fresh parboiled rice hulls serve as an alternative to perlite in greenhouse crop substrates. HortScience 39: 232-235. Eudoxie, G.D. and I.A. Alexander. 2011. Spent mushroom substrate as a transplant media replacement for commercial peat in tomato seedling production. J. Agr. Sci. 3: 41-49. Food and Agriculture Organization of the United Nations (FAO). 2012. State of world fisheries and aquaculture 2012, Rome. Fain, G.B., C.H. Gilliam, J.L. Sibley, and C.R. Boyer. 2008. Wholetree substrates derived from three species of pine in production of annual Vinca. HortTechnology 18: 13-17. García-Delgado, M., M.S. Rodríguez-Cruz, L.F. Lorenzo, M. Arienzo, and M.J. Sánchez Martín. 2007. Seasonal and time variability of heavy metal content and of its chemical forms in sewage sludges from different wastewater treatment plants. Sci. Total Environ. 382:82-92. Gorbe, E. and A. Calatayud. 2010. Optimization of nutrition in soilless system: A review. Adv. Bot. Res. 53: 193-245. Gruda, N. and G.H. Schnitzler. 2004. Suitability of wood fiber substrates for production of vegetable transplants II. The effect of wood fiber substrates and their volume weights on the growth of tomato transplants. Sci. Hort. 100: 333-340. Hicklenton, P.R., V. Rodd, and P.R. Warman. 2001. The effectiveness and consistency of source separated municipal solid waste and bark composts as components of container grown media. Sci. Hort. 91: 365-378. Herrera, F., J.E. Castillo, A.F. Chica, L. Lopez Bellido. 2008. Use of municipal solid waste compost (MSWC) as a growing medium in the nursery production of tomato plants. Bioresour. Technol. 99: 287-296. Jahromi, M.A., A. Aboutalebi and M. H. Farahi. 2012. Influence of different levels of garden compost(garden wastes and cow manure) on growth and stand establishment of tomato and cucumber in greenhouse condition. African J. Biotech. 11: 9036-9039. Kirsten, W.J. 1979. Automated methods for the determination of carbon, hydrogen, nitrogen, and sulfur alone in organic and inorganic materials. Anal. Chem. 51: 1173-1179. Lazcano, C., J. Arnold, A. Tato, J.G. Zaller and J. Domínguez. 2009. Compost and vermicompost as nursery pot components: effects on tomato plant growth and morphology. Span. J. Agri. Res. 7: 944-951. Levy, J.S. and B.R. Taylor. 2003. Effects of pulp mill solids and three composts on early growthof t omatoes. Bioresour. Technol. 89: 297-305. Marble, S.C., C.H. Gilliam, J.L. Sibley, G.B. Fain, H.A. Torbert, T.V. Gallagher, and J.W. Olive. 2010. Evaluation of composted poultry litter as a substrate amendment for wholetree, clean chip residual, and pinebark for container grown woody nursery crops. J. Environ. Hort. 28: 107-116. Melgar-Ramirez, R. and M.I. Pascual-Alex. 2010. Characterization and use of a vegetable waste vermicompost as an alternative component in substrates for horticultural seedbeds. Span. J. Agric. Res. 8(4): 1174-1182. Nair, D.N.S. 2006. Recycling aquacultural waste through horticultural greenhouse production as a resource recovery approach. MS Thesis, Department of Environmental Engineering, Virginia Polytechnical and State University, Blacksburg, VA. Naylor, S.J., R.D. Moccia, and G.M. Durant. 1999. The chemical composition of settleable solid fish waste (manure) from commercial rainbow trout farms in Ontario, Canada. N. Am. J. Aquacult. 61:21-26. Palada, M.C., W.M. Cole, and S.M.A. Crossman. 1999. Influence of effluents from intensive aquaculture and sludge on growth and yield of bell peppers. J. Sustain. Agr. 14:85-103. Pantanella, E., J.J. Danaher, J.E. Rakocy, R.C. Shultz, and D.S. Bailey. 2011. Alternative media types for greenhouse seedling production of lettuce and basil. Acta Hort. 891: 257-264. Rakocy, J., R.C. Shultz, D.S. Bailey, and E.S. Thoman. 2003. Aquaponic production of tilapia and basil: Comparing a batch and staggered cropping system. Acta Hort. 648: 63-69. Ray, A.J, K.S. Dillon, and J.M. Lotz. 2010. Water quality dynamics and shrimp (Litopenaeus vannamei) production in intensive, mesohaline culture systems with two levels of biofloc management. Aquacult. Eng. 43: 83-93. Ribeiro, H.M., A.M. Romero, H. Pereira, P. Borges, F. Cabral, and E. Vasconcelos. 2007. Evaluation of a compost obtained from forestry wastes and solid phase of pig slurry as a substrate for seedlings production. Bioresour. Technol. 98: 3294-3297. Sharrer, M.J., K.L. Rishel, and S. Summerfelt. 2009. Evaluation of geotextile filtration applying coagulant and flocculant amendments for aquaculture biosolids dewatering and phosphorus removal. Aquacult. Eng. 40:1-10. Sims, G.K., T.R. Ellsworth, and R.L. Mulvaney. 1995. Microscale determination of inorganic nitrogen in water and soil extracts. Commun. Soil Sci. Plant Anal. 26: 303-316. Silva, R. 2000. Recommended plant tissue nutrient levels for some vegetable, fruit, and ornamental foliage and flowering plants in Hawaii in Plant Nutrient Management in Hawaii’s Soils, Approaches for Tropical and Subtropical Agriculture (J. A. Silva and R. Uchida, eds.) College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Subler, S., C.A. Edwards, and J. Metzger. 1998. Comparing vermicomposts and composts. BioCycle 39: 63-66. Theunissen, J., P.A. Ndakidemi and C.P. LaubscherInter. 2010. Potential of vermicompost produced from plant wasteon the growth and nutrient status in vegetable production. Int. J. Phys. Sci. 5: 1964-1973. Tyler, H.H., S.L. Warren, T.E. Bilderback, and W.C. Fonteno. 1993. Composted Turkey litter: I. Effect on chemical and physical properties of a Pine Bark substrate. J. Environ. Hort. 11: 131-136. Wright, R.D. 1986. The pour-through nutrient extraction procedure. HortScience 21: 227-229. Yeager, T., T. Bilderback, D. Fare, C. Gilliam, J. Lea-Cox, A. Niemiera, J. Ruter, K. Tilt, S. Warren, T. Whitwell, and R. Wright. 2007. Best management practices: Guide for producing nursery crops. 2nd ed. Southern Nursery Association, Atlanta, GA.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

Peer?reviewed Paper Danaher, J.J., J.M. Pickens, J.L. Sibley, J.A. Chappell, T.R. Hanson, and C.E. Boyd. 2013. Growth of tomato seedlings in commercial substrate amended with dewatered aquaculture effluent. International Journal of Vegetable Science. DOI:10.1080/19315260.2013.809622 Dissertation Danaher, J.J. 2013. Phytoremediation of aquaculture effluent using integrated aquaculture production systems. Ph.D. Dissertation, Auburn University, Auburn, Alabama. Oral presentations at conferences Danaher, J.J., J.M. Pickens, J.A. Chappell, J.L. Sibley, T.R. Hanson, and C.E. Boyd. 2013. Potential benefits of aquaculture effluent. Aquaculture America 2013, February 21 ? 25, Nashville, Tennessee, USA. Danaher, J.J., J.M. Pickens, J.L. Sibley, J.A. Chappell, T.R. Hanson, C.E. Boyd. 2012. Research in aquaponics. Aquaculture America 2012, February 29 ? March 2, Las Vegas, Nevada, USA. Poster presentation at conferences Danaher, J.J., J.M. Pickens, J.A. Chappell, J.L. Sibley, T.R. Hanson, and C.E. Boyd. 2013. Dewatered aquaculture effluent as substrate amendment for tomato transplant production. Aquaculture America 2013, February 21 ? 25, Nashville, Tennessee, USA. Danaher, J.J., J.L. Sibley, J.A. Chappell, J.M. Pickens, T.R. Hanson, C.E. Boyd. 2013. Growth of tomato (Lycopersicon esculentum) seedlings in commercial substrate amended with dewatered aquaculture effluent. American Society for Horticultural Science, Southern Region Annual Meeting, February 2–5, Orlando, Florida, USA.

Project Outcomes

Project outcomes:

There are many studies evaluating geotextile technology as a method to reduce the overall waste volume on livestock facilities. Aquaculture has adopted this technology to dewater discharged wastes eliminated from RAS production facilities. We found no research analyzing the liquid or solid components created by the geotextile technology. These experiments helped to address potential waste managment strategies for an fish production facility. The solids component has potential for plant production, just like many other livestock wastes. The leachate component appears to have potential for plant production, but will be dependent on the waste managment at individual facilities. As fish facilities become more productive and produce larger quantities of waste with more concentrated nutrient levels they will require methods to remediate the nutrient stream. These trials have provided some potential strategies to manage discharged aquaculture wastes with traditional horticulture plant production technologies.

Farmer Adoption

The farmer may be interested in the geotextile technology to dewater discharged effluent on-site, but additional research will be needed to demonstrate benefits of using the leachate exiting the geotextile bag for hydroponic crop or field crop production.

Recommendations:

Areas needing additional study

Future experiments should evaluate the solid component as a partial substrate replacement and nutrient source for containerized plants requiring longer growth periods. Also, evaluating growth response of plants with a tolerance for high substrate pH (>7.0) and soluble salt concentration (>3.5 mS?cm-1) would benefit aquaculture production facilities handling large amounts of dewatered effluent by providing a practical method to utilize greater quantities of their treated waste for plant production. Furthermore, monitoring macronutrient (i.e. nitrogen and phosphorus) concentrations leaching from the plant container when applying the solid or liquid component for plant production will further address waste management strategies aimed to optimize nutrient use within integrated production systems. Finally, the solid component could be evaluated for field production of vegetable crops or as a feed stuff for livestock or fish production.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.