Lettuce production in hydroponic and fish-farming aquaponic under different channel slopes and nutrient solutions in the NFT system
Metadata
- Cite key: mendoncaLettuceProductionHydroponic2023
- Item type: Journal Article
- Authors: V.V.O. Mendonça, C.A. da Silva, C.R.O.S.G. Mendonça, C.J. da Silva, C.M. Guimarães
- Affiliation: Instituto Federal Goiano/Campus Morrinhos, Morrinhos, GO, Brazil (all authors); research conducted at ‘Sonho Verde’ nursery, Itumbiara, GO, Brazil, in partnership with the Instituto Federal Goiano
- Journal: Revista Brasileira de Engenharia Agrícola e Ambiental 27(9) (2023) 746-754
- Date: 06/2023
- Date added: 2024-02-09
- DOI: 10.1590/1807-1929/agriambi.v27n9p746-754
- Funding: [not reported] — the Acknowledgment section thanks “the Instituto Federal Goiano, Morrinhos Campus, GO, Brazil, for the technical, scientific, and structural support throughout the research” (p.753), but no funding agency, grant number, or scholarship is named.
- URL: https://doi.org/10.1590/1807-1929/agriambi.v27n9p746-754
- PDF:
Mendonça et al. - 2023 - Lettuce production in hydroponic and fish-farming .pdf
Opinion
A tightly designed 3×5 split-plot factorial (nutrient solution × channel slope) with real replication, ANOVA/Tukey and regression analysis — methodologically one of the more rigorous NFT-slope studies in the vault. Its main limitation for cross-study comparison is that almost nothing about the fish side is reported in absolute terms (no stocking density in kg/m³, no FCR, no survival, no final weight), so the aquaponic “treatment” is really just “wastewater from a 15%- or 18%-protein-fed tilapia system,” not a fully characterized fish trial. The channel-slope finding (8% optimal) and the crude-protein finding (18% > 15% ≈ HS) are both clean and well supported by consistent table/text agreement, aside from one apparent typo in the running text for one dry-mass figure.
Abstract
The slope of cultivation channels and types of nutrient solutions in hydroponics and aquaponics influence nutrient absorption and plant production. This research aimed to evaluate lettuce production under different channel slopes and nutrient solutions in hydroponic and aquaponic systems using the nutrient film technique (NFT). A randomized block design was used, with three replicates, in a 3 × 5 split-plot scheme, with three nutrient solutions (conventional hydroponic solution and two wastewaters from the tilapia fish diets, with 15 and 18% of crude protein) and five slopes (2, 4, 6, 8 and 10%) of cultivation channels (PVC tubes). The following variables were evaluated: fresh and dry mass of shoot and roots and the chemical elements of the solutions. In the tilapia feed, the nutrient solution with 18% of protein (wastewater) provides greater production and accumulation of nutrients (N and P) in the lettuce shoot. The slope of 8% on cultivation channels provides greater production of iceberg lettuce, cultivar Lucy Brown. The different slopes and nutrient solutions studied did not influence the potassium (K) accumulation in the lettuce shoot.
Summary
The authors grew iceberg lettuce (cv. Lucy Brown) in NFT (nutrient film technique) PVC-pipe channels fed by three nutrient sources — a conventional hydroponic solution (HS) and two tilapia aquaponic wastewaters from diets with 15% (WS15%) or 18% (WS18%) crude protein — crossed with five channel slopes (2, 4, 6, 8, 10%) in a randomized-block, 3×5 split-plot design with three replicate blocks. They measured shoot and root fresh/dry mass, root length, the root:shoot dry-mass ratio, channel flow rate, and macro/micronutrient concentrations in both the nutrient solutions and the lettuce shoot tissue at 26 days after transplanting. The 18%-protein aquaponic wastewater produced the highest shoot and root biomass and the greatest nitrogen and phosphorus accumulation in the shoot, exceeding both the 15%-protein wastewater and the conventional hydroponic solution; potassium accumulation did not differ among the three solutions. Across all three nutrient sources, an 8% channel slope maximized lettuce production, with lower slopes (2-4%) associated with reduced growth attributed to a longer nutrient-solution contact time and greater osmotic/salinity stress on the roots. The study reports fish-side management (feeding protocol, biofiltration, target water-quality ranges) largely in qualitative or target terms rather than as measured trial outcomes (no stocking density in kg/m³, FCR, survival, or final fish weight are given).
Experiment data
- Location: ‘Sonho Verde’ nursery, Itumbiara, GO, Brazil (18°24’58.6” S, 49°15’12.8” W, 885 m altitude), partnered with Instituto Federal Goiano, Morrinhos Campus
- Design: Randomized block design, 3 replicates, 3×5 split-plot: nutrient solution (HS / WS15% / WS18%) as main plot × channel slope (2/4/6/8/10%) as subplot
- Replicates / n: 3 (blocks)
- Duration: Research conducted March-April 2020 (lettuce cycle: harvest 26 days after transplanting); total fish-side duration not stated as a single figure — see Extraction notes
- Organisms: Tilapia (Oreochromis niloticus) / Lettuce (Lactuca sativa, cv. Lucy Brown, iceberg type)
- Statistics: ANOVA (F-test), Tukey test (p≤0.05) for nutrient-solution comparisons; regression analysis for channel-slope means
- Shoot fresh mass: 448.30 g/plant (WS15%) vs 483.60 g/plant (WS18%) vs 468.60 g/plant (HS), all at the 8% channel slope — WS18% highest, WS15% lowest
- Nitrogen accumulation (N-leaf/N-solution ratio): WS18% (20.5-24.6) significantly higher than WS15% and HS (both 17.5-19.6), across all slopes
Channel slope effect
This paper: Nutrient solutions and channel slopes both had a significant effect (p≤0.01) on all evaluated variables except the K-leaf/K-solution ratio, with a significant solution × slope interaction on the same variables (Table 3, p.750). Flow rate (Q) increased linearly with slope for all three solutions (+0.99, +0.98, +1.06 L h⁻¹ per 1% slope increase for HS, WS15%, WS18% respectively). Shoot fresh mass (SFM) increased with slope up to 8-9%, then plateaued; the lowest slopes (2, 4%) produced the smallest plants, attributed to longer nutrient-solution contact time increasing osmotic/salinity stress on roots (citing Paulus et al. 2010). The 8% slope produced the highest SFM in all three solutions: 448.30 (WS15%), 483.60 (WS18%), 468.60 (HS) g/plant (p.752).
Compared with:
- todo Furlani et al. 2009 — recommended 2-4% slope for channels up to 30 m in hydroponics (p.747, cited for slope range context).
- todo EMBRAPA 2015 — presented slopes of 8-12% for aquaponics (p.747, cited for slope range context).
- todo Paulus et al. 2010 — saline water with higher EC caused linear reduction of RFM/RDM in hydroponic lettuce; salinity effect lower on roots than shoot (p.752).
Nutrient solution effect
This paper: WS18% gave the highest values of SFM, SDM, RFM, RDM, RL, and RDM/SDM in almost all channel slopes (e.g., SFM increase of 3.2% and 10.0% over HS, attributed to higher N and Mg concentration in the WS18% wastewater). WS15% was the least productive solution, attributed to its lower soluble N (0.193 g kg⁻¹), Ca, Mg, and P content relative to WS18% (p.750-751). Potassium accumulation (K-leaf/K-solution ratio) did not differ significantly among the three solutions or channel slopes (Table 3, p.750) — the only variable not significantly affected by either factor.
Compared with:
- todo Cortez et al. 2009 — wastewater from fish-farming can provide significant levels of most plant essential nutrients except potassium and magnesium, regardless of fish species, requiring mineral supplementation for these two elements (p.749).
- todo Jordan et al. 2018 — higher nitrogen content influences leaf area in aquaponic lettuce (p.750, cited for the N-SFM relationship).
Nutrient solution chemistry (Table 1) and leaf tissue mineral content (Table 2)
This paper: Most macro/micronutrients in both wastewater solutions (WS15%, WS18%) were similar to or greater than the hydroponic solution (HS), except potassium and manganese, which were lower in the wastewaters (Table 1, p.749). Leaf tissue N and P (Table 2, p.749, both dry-matter basis, all systems measured at EC stabilized to 1.8 ± 0.2 dS m⁻¹, 26 DAT) ranged 17.9-21.0 g kg⁻¹ N and 58.1-67.3 g kg⁻¹ K, both described by the authors as adequate ranges (citing Fátima et al. 2018); leaf P (5.65-7.35 g kg⁻¹ DM) was close to the range recommended by EMBRAPA (1999), 4-7 g kg⁻¹ DM. Leaf tissue Fe (1168-1498 mg kg⁻¹ DM) and, to a lesser extent, Mn (141-203 mg kg⁻¹ DM) are markedly high relative to typical lettuce sufficiency ranges; the paper does not comment on this. Full Table 1/Table 2 values are recorded in Experimental Remarks (Table 1, a water-chemistry panel, has no matching trials.csv columns for most of its elements) and in plant_measurements.csv (Table 2, leaf tissue minerals).
Compared with:
- todo Gualberto et al. 1999 — original HS nutrient recipe (NPK+8 nutrients, Forth Hortaliças) used as the hydroponic control formulation in this study (p.747).
Linked claims
- Channel slope affects nutrient film technique lettuce production independently of nutrient source
- Aquaponic wastewater from a higher-protein fish diet increases nitrogen and phosphorus accumulation in lettuce shoot tissue
- Potassium accumulation in lettuce shoot is not affected by aquaponic vs hydroponic nutrient source
Citations to chase
- todo Furlani et al. (2009) — recommended channel slope range for hydroponics
- todo EMBRAPA (2015) — recommended channel slope range for aquaponics; general aquaponic system design manual cited throughout Methods
- todo Paulus et al. (2010) — salinity effects on hydroponic lettuce root/shoot growth
- todo Cortez et al. (2009) — fish-farming wastewater nutrient content, K/Mg deficiency
- todo Jordan et al. (2018) — nitrogen effect on aquaponic lettuce leaf area
- todo Gualberto et al. (1999) — hydroponic nutrient solution recipe used as HS control
- todo Fátima et al. (2018) — reference ranges for adequate N and K leaf tissue content in lettuce
Extraction notes
⚠️WARN-MATERIAL — Shoot dry mass (SDM), WS18% at 8% channel slope. Table 4 (p.750) reports SDM for WS18% at the 8% slope as “19.70” (g/plant). The Results running text (p.752) restates the same 8%-slope headline figures as “SDM values of 17.90, 18.30, and 9.70 g per plant, for HS, WS15%, and WS18%, respectively” — i.e. 9.70, not 19.70. The HS (17.90) and WS15% (18.30) figures in that same sentence match Table 4 exactly, and the parallel SFM sentence immediately before it also matches Table 4 exactly (468.60/448.30/483.60), so only the WS18% SDM figure is affected. 9.70 would also break the otherwise monotonic increase with slope in Table 4’s WS18% SDM column (9.00, 13.20, 15.60, then supposedly dropping to 9.70, then rising again to 17.50) and would fall below even the 6% and 4% slope values — internally inconsistent within the table itself. Table 4’s value (19.70) is recorded as the more reliable figure (most likely a dropped leading digit in the text, “19.70” → “9.70”); the text’s “9.70” is noted here but not used. Affects: Plant dry matter cell for T2 only.
⚠️WARN-MINOR — Shoot dry mass (SDM) formatting artifact, WS15% at 8% slope. Table 4 (p.750) prints this cell as “18,.30” (comma followed by period). Read as 18.30 — consistent with the neighbouring slope values (14.10 at 6%, 15.00 at 10%) and with the Results text (p.752), which states “18.30” plainly for this same cell. No competing value exists; this is treated as a typesetting artifact, not a genuine contradiction, and does not affect the recorded value.
[not reported] (grouped by field, both trials): Fish Category; Initial Stock density (see below); FCR; SGR; N, P, K (feed elemental composition, only crude protein % given); % of body weight (daily ration given in g/day, not %); Fish size final; Total Feed (kg, cumulative); Fish biomass created (kg); Fish survival rate; Fish weight gain; Fish trial duration (days, as a single figure); Water classification; Daily Water exchange rate (stated as an interval — “50% every 30 days” — not a daily %, so not converted); Dissolved Oxygen (monitored per Methods p.748 but no summary value given in Results); Water temperature (monitored per Methods p.748 but no summary value given; Figure 1 gives air, not water, temperature); TAN/NH4-N and NO2-N (only upper-limit targets stated, “below 2.0 mg/L” and “below 0.5 mg/L” respectively — not measured trial means); Plant Category; Plants/m² (not stated; channel length, hole spacing and channel spacing are all given but combining them into a density would be derivation); SPAD; Plant height; Leaf count; Tissue nitrate AP/HYD (no tissue nitrate assay in this paper — Table 2 measures N, P, K, Ca, Mg, S, Cu, Fe, Mn, Zn, not nitrate); AP, HYD (see note below); Average room Temperature (Figure 1 is a line chart with no numeric mean stated in text — not read off the figure per the schema’s figure-reading rule).
NOT DERIVED, left NR: Initial Stock density — the paper states “60 juveniles per box, for a final storage density of 60 kg of live fish per m³ of water” (p.747-748); this is explicitly a final, not initial, density, and the schema column is defined as initial only, so it is NR here (the final figure is preserved as a NO COLUMN item below). Fish size initial is given only as an approximation (“about 100 g each,” p.748) and recorded as such, not treated as a precise mean. Daily Water exchange rate: solution “renewed every 30 days, replacing 50% of the volume” (p.748) is an interval-based statement; converting to a %/day figure (50/30 ≈ 1.67%/day) would be derivation, so left NR. Plants/m²: channel is 3.0 m long with 10 planting holes (25 cm apart) and channels are spaced 30 cm apart (p.747) — sufficient to compute a density, but not derived.
NO COLUMN items (recorded in Experimental Remarks in trials.csv, no matching schema column):
- Table 1 (nutrient-solution chemistry panel, tanks, 26 DAT): full Ca, Mg, S, Cu, Mn, Zn, B, Cd, Pb, Ni, Cr concentrations for WS15%, WS18%, HS — this is a water-chemistry panel with no home in the trials.csv water-quality columns (which only cover TAN/NH4-N, NO2-N, NO3-N, EC, pH, DO, temperature). Flagging per SCHEMA.md: this water panel seems too valuable to discard entirely — see point 7 of the report.
- Root fresh matter (RFM), root dry matter (RDM), root length (RL), and the RDM/SDM ratio (Table 3/4, p.750) — none of these have a dedicated trials.csv column. Full per-slope breakdown (2/4/6/8/10%) recorded per trial below.
- Table 5 (p.752): N-leaf/N-solution and P-leaf/P-solution ratios accumulated over the cycle, by solution × slope — no dedicated column; WS18% (20.5-24.6 for N-ratio) was significantly higher than WS15% and HS (both ~17.5-19.6) at every slope; P-ratio pattern was more mixed (WS15%/HS higher than WS18% at the 2% slope only; no difference among solutions at 4%; WS18% highest at 6/8/10%). K-leaf/K-solution ratio was not significantly affected by solution or slope (the paper’s only null result, restated in Conclusion #3).
- Site altitude: 885 m (p.747).
- Flow rate (Q) was measured twice: once before transplanting, without root systems present, giving 16.5/18.1/20.3/21.6/23.4 L h⁻¹ at slopes 2/4/6/8/10% (not broken down by solution at this point), and again at 25 days after transplanting, with roots present and broken down by solution (Table 4) — these are explicitly two different, clearly labelled measurement times, not a contradiction. The 25-DAT, per-solution values are the ones used for
Water recycle.
Type classification rationale: experiment — randomized block design, 3×5 split-plot with true replication (3 blocks), defined treatments (nutrient solution × channel slope), and formal statistical testing (ANOVA/Tukey/regression). No review or modelling component; all data are original measurements from this trial.
AP / HYD columns: Populated with the per-plant shoot fresh mass (SFM) at the 8% slope (this paper does not report an area-based yield, e.g. g/m² or kg/m², anywhere), since Plants/m² could not be derived to convert to an area basis. This differs from the per-m² convention used in some other notes in this vault (e.g. alcarrazQualityLettuceLactuca2018); flagging the unit choice explicitly since AP/HYD unit normalisation is listed as an open schema question.
New tags introduced: None. Meta/Type/Experiment, Meta/Region/South-America, Meta/Fish/Tilapia, Meta/Plant/Lettuce are all reused from existing vault entries (e.g. barbosaPerformanceNileTilapia2020, dasilvaProductionTambaquiJuveniles2025).
Quality tally: 0 ⚠️BLOCK, 1 ⚠️MATERIAL (SDM WS18% at 8% slope, text vs. table), 2 ⚠️MINOR (SDM comma/period formatting artifact; unrelated unit mislabel of the dimensionless RDM/SDM ratio as “g per plant” in running text, p.752, which does not affect any extracted cell). Score: ok (0 BLOCK and ≤2 MATERIAL).
Source: Mendonça et al. - 2023 - Lettuce production in hydroponic and fish-farming .pdf
Data Tables
Structured data extracted from this paper into the vault's
trials.csv/plant_measurements.csvdatasets. Fields the paper didn't report are omitted. Download the full datasets (measurements).
Trial Parameters
mendoncaLettuceProductionHydroponic2023-T1
Fish
| Field | Value |
|---|---|
| Fish | Tilapia (Oreochromis niloticus) |
| Protein | 15 |
| Fish size initial | 100 (stated as ‘about 100 g each’, p.748; approximate, not a precise stated mean) |
| Feed routine | Twice daily, 50% at 9:00 and 50% at 16:00 (p.748) |
| Feed regime | Feed type/amount/particle size adjusted to tilapia live weight and development stage (juvenile, growth, fattening); ~75 g/day (60 fish/box, week 1) gradually increased to 200 g/day by week 9; feeding rate and fish numbers adjusted per weekly ammonia/nitrate monitoring (p.748) |
Water
| Field | Value |
|---|---|
| Water recycle | 0.308 (L/min, at 8% channel slope, 25 days after transplanting; UNIT CONVERSION ONLY: 18.5 L/h -> L/min; full per-slope breakdown (L/h) 12.5/14.2/17.2/18.5/20.1 (slopes 2/4/6/8/10%); pre-transplant calibration values were 16.5/18.1/20.3/21.6/23.4 L/h at slopes 2/4/6/8/10%, not broken down by solution — see Extraction notes) |
| Water volume in the system | 1000 (L, per tank; total system volume incl. 200 L biofilter + channel volume not stated, p.747) |
| Water type | Wastewater from tilapia (Oreochromis niloticus) aquaculture, diet with 15% crude protein (p.747) |
| Aq pH | 6.0-6.5 (post-biofilter average, feeding the NFT channels; range of stated averages, no single trial mean, p.748) |
| pHOptimal | 6.4-6.8 (target range maintained via limestone reservoir addition/removal, p.748) |
| EC | 1.8 +/- 0.2 (dS/m, stabilized value at time of Table 2 tissue sampling, 26 DAT, p.749; broader observed range across the cycle 1.2-2.0 mS/cm [=dS/m] also reported, p.748 — compatible, not conflicting, not used as the primary value) |
| NO3-N | 10 (mg/L, stated as ‘maintained at around 10 mg/L’ using a Speedy Test kit, p.748; an operational target restated as achieved, not a formal trial-mean statistic) |
Plant
| Field | Value |
|---|---|
| Plant | Iceberg lettuce (Lactuca sativa), cv. Lucy Brown |
| Details | Seedlings from a commercial nursery, adapted to local climate conditions; harvested 26 days after transplanting (p.748) |
| Days Plant after transplant | 26 |
| Plant fresh weight | 448.3 (g/plant, at 8% channel slope — the paper’s own highlighted/recommended slope, restated in running text p.752; full per-slope breakdown 149.7/243.5/348.5/448.3/385.0 (slopes 2/4/6/8/10%) in Experimental Remarks, Table 4 p.750) |
| Plant dry matter | 18.3 (g/plant dry weight, at 8% slope; Table 4 p.750 prints this cell as ‘18,.30’ — read as 18.3, WARN-MINOR formatting artifact, see Extraction notes; full per-slope breakdown 8.6/12.6/14.1/18.3/15.0 (slopes 2/4/6/8/10%)) |
System & Setup
| Field | Value |
|---|---|
| System type | Nutrient Film Technique (NFT), PVC tube channels (p.747) |
| Media Details | PVC pipe channel, 100 mm diameter, 3.0 m long, perforations every 25 cm (10 plants/channel); channel-to-channel spacing 30 cm; cultivation bench 1.2 m wide x 3 m long, ~1.0 m average height, built from pallets/wooden slats/nails; slopes tested 2/4/6/8/10% (p.747) |
| Biological system already in use | N (New biofilter cycled for ~30 days after tilapia juvenile introduction, before plants were introduced, to establish nitrification equilibrium (p.747)) |
| pH Buffers | Y (Limestone reservoir used to raise/adjust solution pH as needed, target range 6.4-6.8 (p.748); HS pH specifically raised from 5.7 to ~6.2 via the limestone reservoir (p.749)) |
| Nutrient supplemented | Y (Aquaponic (WS15%): no added nutrient solution, wastewater only; no supplementation applied despite the Discussion (p.749) noting fish wastewater aquaponics may generally need K/Mg supplementation (citing Cortez et al. 2009). Hydroponic control (HS): NPK+8 nutrients organic fertilizer (Forth Hortalicas(TM)), per Gualberto et al. 1999, applying per liter: 236.3 mg N, 39.0 mg P, 224.9 mg K, 228.0 mg Ca, 33.7 mg Mg, 46.3 mg S, 0.24 mg B, 0.02 mg Cu, 5.0 mg Fe, 0.23 mg Mn, 0.03 mg Mo, 0.05 mg Zn (p.747).) |
| Equipment | Digital timer (40 settings); three centrifugal motor pumps, 1000 L/h each, 23 mca head, 1/2 hp; PVC tube channels 100 mm diameter; 13 mm buried polyethylene supply pipe; 5x7 mm flexible microtubes per plot; 200 L biological filter with 67.1 L expanded clay per fish tank; thermometer with datalogger; pH meter; Prodac Tape Test Ph Gh Kh NO2 NO3 Cl2 (‘Speedy Test’) test strips |
| Control Parameters | pH target 6.4-6.8; EC kept below 1.8 mS/cm target (achieved ~1.8+/-0.2 dS/m at 26 DAT); ammonia kept below 2.0 mg/L; nitrite kept below 0.5 mg/L; nitrate maintained around 10 mg/L |
| Combination | Tilapia (Oreochromis niloticus, 15% crude protein diet) and iceberg lettuce cv. Lucy Brown; NFT PVC channels; aquaponic wastewater vs conventional hydroponic solution (HS) control; crossed with 5 channel slopes (2,4,6,8,10%) |
Site
| Field | Value |
|---|---|
| Region | South America |
| Country | Brazil |
| Lat | -18.4163 |
| Long | -49.2536 |
Results & Statistics
| Field | Value |
|---|---|
| Measured Unit | g/plant (SFM, SDM, RFM, RDM); cm (RL); dimensionless (RDM/SDM); L/h (Q); g/kg or mg/kg dry matter (leaf nutrient concentration, Table 2) |
| Statistic Details | Analysis of variance (F-test); Tukey test p<=0.05 for nutrient-solution mean separation; regression analysis for channel-slope means; randomized block design, 3 replicate blocks, 3 nutrient solutions x 5 slopes split-plot (solution = main plot, slope = subplot) |
| Statistically analysed | Y |
| Replicates (n) | 3 |
| AP | 448.3 (g/plant SFM at 8% slope; this trial’s aquaponic treatment; see Plant fresh weight cell) |
| HYD | 468.6 (g/plant SFM at 8% slope; paired HS control, same value repeated for both T1 and T2 per schema convention) |
Experimental Remarks: TRIAL DEFINITION: T1 = aquaponic treatment using tilapia wastewater from a 15% crude-protein diet (WS15%), grown in NFT PVC channels crossed with 5 channel slopes (2,4,6,8,10%) as a sub-plot factor in a 3x5 split-plot design (3 replicate blocks). Paired control = conventional hydroponic solution (HS, per Gualberto et al. 1999), recorded in the HYD-side columns (Water type=NA does not apply here — HS is a real tested arm in this paper, its own values are carried in HYD/AP-comparison columns only, not as a separate trial row), tested under the identical 5-slope sub-plot design and repeated identically for T1 and T2 as instructed by the schema. | NO COLUMN — Table 1 nutrient-solution chemistry (tanks, 26 DAT, mg or g per kg as stated in the paper): WS15%: N 0.193 g/kg, P 0.071 g/kg, K 0.073 g/kg, Ca 0.284 g/kg, Mg 0.165 g/kg, S 0.046 g/kg, Cu 0.32 mg/kg, Fe 18.5 mg/kg, Mn 1.3 mg/kg, Zn 0.312 mg/kg, B 0.615 mg/kg, Pb 0.013 mg/kg, Ni 0.014 mg/kg (Cd and Cr not detected/reported, shown as ’-’ in Table 1). HS (paired control): N 0.239, P 0.064, K 0.426, Ca 0.170, Mg 0.026, S 0.036 g/kg; Cu 0.045, Fe 5.000, Mn 0.480, Zn 0.300, B 0.320 mg/kg; Cd/Pb/Ni/Cr not detected/reported. This is a water-chemistry panel with no matching trials.csv columns for most elements; flagged in the note as too valuable to discard. | NO COLUMN — root traits (Table 4, p.750, g/plant unless noted), no dedicated column: RFM (root fresh matter) across slopes 2/4/6/8/10 slope (headline) values: RFM 58.1, RDM 3.1, RL 17.5, RDM/SDM 0.17. HS (paired control, same slopes): RFM = 40.5/51.7/59.6/61.2/56.2 (slopes 2/4/6/8/10%); RDM = 1.01/1.45/2.8/3.8/2.4 (slopes 2/4/6/8/10%); RL = 12.4/15.2/15.9/16.5/16.5 (slopes 2/4/6/8/10%); RDM/SDM = 0.11/0.11/0.2/0.21/0.16 (slopes 2/4/6/8/10%); 8%% slope: RFM 61.2, RDM 3.8, RL 16.5, RDM/SDM 0.21. | NO COLUMN — Table 5 (p.752) N-leaf/N-solution and P-leaf/P-solution ratios (accumulated over the cycle, by slope): see paired note in the other trial row / the paper’s note for the full breakdown; headline: WS15% N-ratio significantly higher than the other two solutions at every slope; P-ratio pattern mixed (WS15%/HS higher only at 2% slope, no difference at 4%, WS18% highest at 6/8/10%). K-leaf/K-solution ratio not significant for solution or slope (paper’s Conclusion #3). | NO COLUMN — site altitude: 885 m (p.747). | NOT DERIVED, left NR: Initial Stock density (paper states a FINAL storage density of 60 kg live fish/m3 for 60 juveniles/box, p.747-748 — explicitly final, not initial, so the Initial Stock density cell is NR; the final figure is preserved here as NO COLUMN: final storage density = 60 kg/m3); FCR; SGR; Total Feed (kg, cumulative — only a daily g/day progression is given, 75 g/day week 1 rising to 200 g/day by week 9); Fish biomass created (kg); Fish survival rate; Fish weight gain; Fish trial duration as a single day-count (paper states the overall research period as ‘March to April 2020’ [~61 days max] and separately describes a feed progression ‘up to the ninth week’ [~63 days] — these are not presented as two answers to the same explicit question, so not flagged as a contradiction, but neither yields a clean total duration, hence NR); % of body weight (feed given in g/day, not %); N/P/K feed composition (only crude protein % given); Daily Water exchange rate as a %/day figure (paper states ‘renewed every 30 days, replacing 50% of the volume’, p.748 — converting to ~1.67%/day would be derivation); Plants/m2 (channel length 3.0 m, 10 holes/channel 25 cm apart, channel spacing 30 cm are all given, p.747, but combining them into a density would be derivation). | AP/HYD columns populated with per-plant SFM at the 8% slope (no area-based yield, e.g. g/m2 or kg/m2, is reported anywhere in this paper, and Plants/m2 could not be derived to convert to an area basis); differs from the per-m2 convention used in some other notes in this vault — flagging the unit choice explicitly since AP/HYD unit normalisation is an open schema question. | Nutrient supplemented details: Aquaponic (WS15%): no added nutrient solution, wastewater only; no supplementation applied despite the Discussion (p.749) noting fish wastewater aquaponics may generally need K/Mg supplementation (citing Cortez et al. 2009). Hydroponic control (HS): NPK+8 nutrients organic fertilizer (Forth Hortalicas(TM)), per Gualberto et al. 1999, applying per liter: 236.3 mg N, 39.0 mg P, 224.9 mg K, 228.0 mg Ca, 33.7 mg Mg, 46.3 mg S, 0.24 mg B, 0.02 mg Cu, 5.0 mg Fe, 0.23 mg Mn, 0.03 mg Mo, 0.05 mg Zn (p.747). | Water type: Wastewater from tilapia (Oreochromis niloticus) aquaculture, diet with 15% crude protein (p.747)
mendoncaLettuceProductionHydroponic2023-T2
Fish
| Field | Value |
|---|---|
| Fish | Tilapia (Oreochromis niloticus) |
| Protein | 18 |
| Fish size initial | 100 (stated as ‘about 100 g each’, p.748; approximate, not a precise stated mean) |
| Feed routine | Twice daily, 50% at 9:00 and 50% at 16:00 (p.748) |
| Feed regime | Feed type/amount/particle size adjusted to tilapia live weight and development stage (juvenile, growth, fattening); ~75 g/day (60 fish/box, week 1) gradually increased to 200 g/day by week 9; feeding rate and fish numbers adjusted per weekly ammonia/nitrate monitoring (p.748) |
Water
| Field | Value |
|---|---|
| Water recycle | 0.322 (L/min, at 8% channel slope, 25 days after transplanting; UNIT CONVERSION ONLY: 19.3 L/h -> L/min; full per-slope breakdown (L/h) 13.2/14.8/17.9/19.3/21.6 (slopes 2/4/6/8/10%); pre-transplant calibration values were 16.5/18.1/20.3/21.6/23.4 L/h at slopes 2/4/6/8/10%, not broken down by solution — see Extraction notes) |
| Water volume in the system | 1000 (L, per tank; total system volume incl. 200 L biofilter + channel volume not stated, p.747) |
| Water type | Wastewater from tilapia (Oreochromis niloticus) aquaculture, diet with 18% crude protein (p.747) |
| Aq pH | 6.0-6.5 (post-biofilter average, feeding the NFT channels; range of stated averages, no single trial mean, p.748) |
| pHOptimal | 6.4-6.8 (target range maintained via limestone reservoir addition/removal, p.748) |
| EC | 1.8 +/- 0.2 (dS/m, stabilized value at time of Table 2 tissue sampling, 26 DAT, p.749; broader observed range across the cycle 1.2-2.0 mS/cm [=dS/m] also reported, p.748 — compatible, not conflicting, not used as the primary value) |
| NO3-N | 10 (mg/L, stated as ‘maintained at around 10 mg/L’ using a Speedy Test kit, p.748; an operational target restated as achieved, not a formal trial-mean statistic) |
Plant
| Field | Value |
|---|---|
| Plant | Iceberg lettuce (Lactuca sativa), cv. Lucy Brown |
| Details | Seedlings from a commercial nursery, adapted to local climate conditions; harvested 26 days after transplanting (p.748) |
| Days Plant after transplant | 26 |
| Plant fresh weight | 483.6 (g/plant, at 8% channel slope — the paper’s own highlighted/recommended slope, restated in running text p.752; full per-slope breakdown 160.7/267.1/365.7/483.6/414.7 (slopes 2/4/6/8/10%) in Experimental Remarks, Table 4 p.750) |
| Plant dry matter | 19.7 (g/plant dry weight, at 8% slope, Table 4 p.750; ⚠️WARN-MATERIAL: running text p.752 states this same 8%-slope value as ‘9.70’ — Table 4’s 19.7 is used, see Extraction notes for evidence; full per-slope breakdown 9.0/13.2/15.6/19.7/17.5 (slopes 2/4/6/8/10%)) |
System & Setup
| Field | Value |
|---|---|
| System type | Nutrient Film Technique (NFT), PVC tube channels (p.747) |
| Media Details | PVC pipe channel, 100 mm diameter, 3.0 m long, perforations every 25 cm (10 plants/channel); channel-to-channel spacing 30 cm; cultivation bench 1.2 m wide x 3 m long, ~1.0 m average height, built from pallets/wooden slats/nails; slopes tested 2/4/6/8/10% (p.747) |
| Biological system already in use | N (New biofilter cycled for ~30 days after tilapia juvenile introduction, before plants were introduced, to establish nitrification equilibrium (p.747)) |
| pH Buffers | Y (Limestone reservoir used to raise/adjust solution pH as needed, target range 6.4-6.8 (p.748); HS pH specifically raised from 5.7 to ~6.2 via the limestone reservoir (p.749)) |
| Nutrient supplemented | Y (Aquaponic (WS18%): no added nutrient solution, wastewater only; no supplementation applied despite the Discussion (p.749) noting fish wastewater aquaponics may generally need K/Mg supplementation (citing Cortez et al. 2009). Hydroponic control (HS): NPK+8 nutrients organic fertilizer (Forth Hortalicas(TM)), per Gualberto et al. 1999, applying per liter: 236.3 mg N, 39.0 mg P, 224.9 mg K, 228.0 mg Ca, 33.7 mg Mg, 46.3 mg S, 0.24 mg B, 0.02 mg Cu, 5.0 mg Fe, 0.23 mg Mn, 0.03 mg Mo, 0.05 mg Zn (p.747).) |
| Equipment | Digital timer (40 settings); three centrifugal motor pumps, 1000 L/h each, 23 mca head, 1/2 hp; PVC tube channels 100 mm diameter; 13 mm buried polyethylene supply pipe; 5x7 mm flexible microtubes per plot; 200 L biological filter with 67.1 L expanded clay per fish tank; thermometer with datalogger; pH meter; Prodac Tape Test Ph Gh Kh NO2 NO3 Cl2 (‘Speedy Test’) test strips |
| Control Parameters | pH target 6.4-6.8; EC kept below 1.8 mS/cm target (achieved ~1.8+/-0.2 dS/m at 26 DAT); ammonia kept below 2.0 mg/L; nitrite kept below 0.5 mg/L; nitrate maintained around 10 mg/L |
| Combination | Tilapia (Oreochromis niloticus, 18% crude protein diet) and iceberg lettuce cv. Lucy Brown; NFT PVC channels; aquaponic wastewater vs conventional hydroponic solution (HS) control; crossed with 5 channel slopes (2,4,6,8,10%) |
Site
| Field | Value |
|---|---|
| Region | South America |
| Country | Brazil |
| Lat | -18.4163 |
| Long | -49.2536 |
Results & Statistics
| Field | Value |
|---|---|
| Measured Unit | g/plant (SFM, SDM, RFM, RDM); cm (RL); dimensionless (RDM/SDM); L/h (Q); g/kg or mg/kg dry matter (leaf nutrient concentration, Table 2) |
| Statistic Details | Analysis of variance (F-test); Tukey test p<=0.05 for nutrient-solution mean separation; regression analysis for channel-slope means; randomized block design, 3 replicate blocks, 3 nutrient solutions x 5 slopes split-plot (solution = main plot, slope = subplot) |
| Statistically analysed | Y |
| Replicates (n) | 3 |
| AP | 483.6 (g/plant SFM at 8% slope; this trial’s aquaponic treatment; see Plant fresh weight cell) |
| HYD | 468.6 (g/plant SFM at 8% slope; paired HS control, same value repeated for both T1 and T2 per schema convention) |
Experimental Remarks: TRIAL DEFINITION: T2 = aquaponic treatment using tilapia wastewater from a 18% crude-protein diet (WS18%), grown in NFT PVC channels crossed with 5 channel slopes (2,4,6,8,10%) as a sub-plot factor in a 3x5 split-plot design (3 replicate blocks). Paired control = conventional hydroponic solution (HS, per Gualberto et al. 1999), recorded in the HYD-side columns (Water type=NA does not apply here — HS is a real tested arm in this paper, its own values are carried in HYD/AP-comparison columns only, not as a separate trial row), tested under the identical 5-slope sub-plot design and repeated identically for T1 and T2 as instructed by the schema. | NO COLUMN — Table 1 nutrient-solution chemistry (tanks, 26 DAT, mg or g per kg as stated in the paper): WS18%: N 0.247 g/kg, P 0.07 g/kg, K 0.071 g/kg, Ca 0.28 g/kg, Mg 0.17 g/kg, S 0.046 g/kg, Cu 0.33 mg/kg, Fe 19.0 mg/kg, Mn 1.0 mg/kg, Zn 0.33 mg/kg, B 0.62 mg/kg, Pb 0.012 mg/kg, Ni 0.011 mg/kg (Cd and Cr not detected/reported, shown as ’-’ in Table 1). HS (paired control): N 0.239, P 0.064, K 0.426, Ca 0.170, Mg 0.026, S 0.036 g/kg; Cu 0.045, Fe 5.000, Mn 0.480, Zn 0.300, B 0.320 mg/kg; Cd/Pb/Ni/Cr not detected/reported. This is a water-chemistry panel with no matching trials.csv columns for most elements; flagged in the note as too valuable to discard. | NO COLUMN — root traits (Table 4, p.750, g/plant unless noted), no dedicated column: RFM (root fresh matter) across slopes 2/4/6/8/10 slope (headline) values: RFM 65.8, RDM 4.1, RL 18.5, RDM/SDM 0.21. HS (paired control, same slopes): RFM = 40.5/51.7/59.6/61.2/56.2 (slopes 2/4/6/8/10%); RDM = 1.01/1.45/2.8/3.8/2.4 (slopes 2/4/6/8/10%); RL = 12.4/15.2/15.9/16.5/16.5 (slopes 2/4/6/8/10%); RDM/SDM = 0.11/0.11/0.2/0.21/0.16 (slopes 2/4/6/8/10%); 8%% slope: RFM 61.2, RDM 3.8, RL 16.5, RDM/SDM 0.21. | NO COLUMN — Table 5 (p.752) N-leaf/N-solution and P-leaf/P-solution ratios (accumulated over the cycle, by slope): see paired note in the other trial row / the paper’s note for the full breakdown; headline: WS18% N-ratio significantly higher than the other two solutions at every slope; P-ratio pattern mixed (WS15%/HS higher only at 2% slope, no difference at 4%, WS18% highest at 6/8/10%). K-leaf/K-solution ratio not significant for solution or slope (paper’s Conclusion #3). | NO COLUMN — site altitude: 885 m (p.747). | NOT DERIVED, left NR: Initial Stock density (paper states a FINAL storage density of 60 kg live fish/m3 for 60 juveniles/box, p.747-748 — explicitly final, not initial, so the Initial Stock density cell is NR; the final figure is preserved here as NO COLUMN: final storage density = 60 kg/m3); FCR; SGR; Total Feed (kg, cumulative — only a daily g/day progression is given, 75 g/day week 1 rising to 200 g/day by week 9); Fish biomass created (kg); Fish survival rate; Fish weight gain; Fish trial duration as a single day-count (paper states the overall research period as ‘March to April 2020’ [~61 days max] and separately describes a feed progression ‘up to the ninth week’ [~63 days] — these are not presented as two answers to the same explicit question, so not flagged as a contradiction, but neither yields a clean total duration, hence NR); % of body weight (feed given in g/day, not %); N/P/K feed composition (only crude protein % given); Daily Water exchange rate as a %/day figure (paper states ‘renewed every 30 days, replacing 50% of the volume’, p.748 — converting to ~1.67%/day would be derivation); Plants/m2 (channel length 3.0 m, 10 holes/channel 25 cm apart, channel spacing 30 cm are all given, p.747, but combining them into a density would be derivation). | AP/HYD columns populated with per-plant SFM at the 8% slope (no area-based yield, e.g. g/m2 or kg/m2, is reported anywhere in this paper, and Plants/m2 could not be derived to convert to an area basis); differs from the per-m2 convention used in some other notes in this vault — flagging the unit choice explicitly since AP/HYD unit normalisation is an open schema question. | Nutrient supplemented details: Aquaponic (WS18%): no added nutrient solution, wastewater only; no supplementation applied despite the Discussion (p.749) noting fish wastewater aquaponics may generally need K/Mg supplementation (citing Cortez et al. 2009). Hydroponic control (HS): NPK+8 nutrients organic fertilizer (Forth Hortalicas(TM)), per Gualberto et al. 1999, applying per liter: 236.3 mg N, 39.0 mg P, 224.9 mg K, 228.0 mg Ca, 33.7 mg Mg, 46.3 mg S, 0.24 mg B, 0.02 mg Cu, 5.0 mg Fe, 0.23 mg Mn, 0.03 mg Mo, 0.05 mg Zn (p.747). | Water type: Wastewater from tilapia (Oreochromis niloticus) aquaculture, diet with 18% crude protein (p.747)
Plant Measurements
| Trial | System | Category | Analyte | Value | Unit | Sig. | Location |
|---|---|---|---|---|---|---|---|
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Nitrogen (N) | 17.9 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Nitrogen (N) | 20.3 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Nitrogen (N) | 21.03 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Nitrogen (N) | 20.3 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Phosphorus (P) | 6.54 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Phosphorus (P) | 7.35 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Phosphorus (P) | 5.65 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Phosphorus (P) | 7.35 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Potassium (K) | 58.1 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Potassium (K) | 59.1 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Potassium (K) | 67.3 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Potassium (K) | 59.1 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Calcium (Ca) | 17.3 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Calcium (Ca) | 18.05 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Calcium (Ca) | 14.9 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Calcium (Ca) | 18.05 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Magnesium (Mg) | 8.2 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Magnesium (Mg) | 7.5 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Magnesium (Mg) | 6.9 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Magnesium (Mg) | 7.5 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Sulfur (S) | 2.12 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Sulfur (S) | 3.11 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Sulfur (S) | 2.81 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Sulfur (S) | 3.11 | g/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Copper (Cu) | 47.6 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Copper (Cu) | 44.3 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Copper (Cu) | 44.8 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Copper (Cu) | 44.3 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Iron (Fe) | 1284.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Iron (Fe) | 1168.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Iron (Fe) | 1498.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Iron (Fe) | 1168.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Manganese (Mn) | 203.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Manganese (Mn) | 141.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Manganese (Mn) | 162.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Manganese (Mn) | 141.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | AP | mineral | Zinc (Zn) | 235.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T1 | HYD | mineral | Zinc (Zn) | 301.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | AP | mineral | Zinc (Zn) | 267.0 | mg/kg dry matter | NR | Table 2, p.749 |
| mendoncaLettuceProductionHydroponic2023-T2 | HYD | mineral | Zinc (Zn) | 301.0 | mg/kg dry matter | NR | Table 2, p.749 |