Title: The Conflation of iAVs and Sandponics: A Commentary on Sewilam et al., (2022)
Authors: Barry Taylor
DOI: https://doi.org/10.5281/zenodo.17684492
Canonical Source:https://iavs.info/
Abstract
A recent study by Sewilam et al., (2022) conducted a comparative analysis of a sand-based agricultural system. This commentary identifies a terminological inconsistency within the article, specifically the conflation of the proprietary commercial method “Sandponics” with the “Integrated Aqua-Vegeculture System”
(iAVs). These methodologies employ different nutrient sources and operational principles. This conflation led to the omission of pertinent historical data from the literature review and the misattribution of system limitations. This paper clarifies the
distinction between the two technologies and emphasizes the research by McMurtry et al., which addresses the research gap identified by Sewilam et al.
Full Text
- Introduction
Precision in nomenclature is critical for the accurate assessment and classification of
agricultural technologies. Sewilam et al., (2022) define their research focus by stating that
“sandponics (SP), which is also referred to as an Integrated Aqua-Vegeculture system
(iAVs),” is a technique that employs sand filtration in conjunction with fish effluents.
However, existing literature delineates “Sandponics” (a proprietary commercial system
defined by Baba & Ikeguchi, 2015) and “Integrated Aqua-Vegeculture Systems (iAVs)” as
distinct methodologies. This analysis examines the differences between these systems and
illustrates how the interchangeable use of the terms has led to inaccuracies concerning the
historical availability of data and the specific operational constraints of the studied system. - Defining the Distinct Systems
The literature indicates that the two terms describe systems with different nutritional inputs
and mechanical configurations. While Sewilam et al., (2022) employ the term “Sandponics,”
the experimental treatments described (specifically T2, T3, and T4) utilize the functional
architecture of iAVs specifically, the application of aquaculture effluent onto sand beds for
biofiltration and plant growth.
2.1. The Integrated Aqua-Vegeculture System (iAVs)
Developed and characterized across multiple studies (McMurtry et al., 1990b), the Integrated
Aqua-Vegeculture system (iAVs) is a closed system of recirculating water linking fish
production (aquaculture) with sand-cultured vegetable crops (olericulture) (McMurtry et al.,
1990b). The system utilizes unfiltered fish effluent (including solids) pumped directly onto
sand beds (as schematically shown in Figure 1) (McMurtry et al., 1997a). The sand beds
serve simultaneously as the plant growth substrate or plant support (McMurtry et al., 1997a),
a biofilter for the oxidation of reduced nitrogen compounds (McMurtry et al., 1997a), and a
mechanism for particulate removal and the decomposition of waste solids (McMurtry et al.,
1997a). The feasibility of the integrated system was demonstrated using no supplemental
fertilization (McMurtry et al., 1990a), relying exclusively on the mineral nutrition provided
only from fish wastes through biological cycles (McMurtry et al., 1993b).
Fig. 1. Original schematic of the iAVs method. This diagram illustrates the requisite
aquaculture component and direct biological filtration that defines the system. Reproduced
from McMurtry et al., (1990) with the purpose of critical comparison.
2.2. The Sandponics System
The term “Sandponics” is explicitly identified as a trademark or registered trademark of
Sumitomo Electric Industries, Ltd. (Kanazawa et al., 2017).
The proprietary methodology referred to as “Sandponics” (Baba & Ikeguchi, 2015) is
characterized by the use of external chemical inputs. It is described as a unique cultivation
system developed by Sumitomo Electric, using sand as the primary medium (Baba &
Ikeguchi, 2015). The system documentation explicitly lists the inclusion of a “Liquid
fertilizer pump” and a “Liquid fertilizer Dilutor” (see Figure 2) to administer “Standard
Sandponics fertilizer.” Furthermore, the operational protocol addresses agronomic challenges
through chemical adjustment (Baba & Ikeguchi, 2015). This indicates a reliance on manual
chemical intervention to manage water quality, rather than biological nitrification.
Fig. 2. Configuration of the Sandponics System. Reproduced from Baba and Ikeguchi
(2015), “Industrial Cultivation Using the Latest Sandponics System,” SEI Technical Review,
with the purpose of critical comparison.
Kanazawa et al., (2017) describe the evolution of this technology into “New Sandponics”
(NSP) (see Figure 3). This configuration utilizes a basal tank to supply nutrients via the
capillary action of an irrigation cloth. This reliance on chemical fertigation represents a
fundamental divergence from the biological nutrient cycling inherent to iAVs.
Fig. 3: Development of Sandponics devices. Reproduced from Kanazawa (2017), “High
Quality Agricultural Production Support System by Smart Sand Cultivation Device ‘New
Sandponics’,” SEI Technical Review, with the purpose of critical comparison. - Evidence of Existing Literature and the Research Gap
The assertion by Sewilam et al., (2022) that “very little or no scientific literature about
growing crops in sandponics systems hence, creating so many questions related to the
operation, functionality, optimization, sand suitability, and system productivity” (Sewilam et
al., 2022), is directly challenged by the substantial scientific record dating back to the 1980s.
By overlooking the terminology distinction, Sewilam et al., omitted the work of Dr. Mark
McMurtry and colleagues at North Carolina State University (NCSU), which provides
comprehensive, quantitative data on the exact methodology studied.
3.1. Documented System Functionality
Research on iAVs explicitly addressed the operational dynamics, nutrient cycling, and
productivity of sand-based integrated systems, contradicting the claim that such data is
absent.
● Feasibility and Operation: McMurtry et al., (1990) documented the integrated
aquaculture-vegeculture system (iAVs) (McMurtry et al., 1990a, 1990b), which they
described as a closed system of recirculating water (McMurtry et al., 1990a). This
system utilized sand beds as a grow medium (McMurtry et al., 1990a) for the
concurrent production of Blue Tilapia (McMurtry et al., 1990a) and vegetables,
including tomato, cucumber, and bush bean (McMurtry et al., 1990a). The study
successfully demonstrated that the vegetables grown in sand beds provided sufficient
filtration of the recirculated water to maintain water quality acceptable for fish growth
(McMurtry et al., 1993b). The crops achieved adequate mineral nutrition solely from
fish wastes (McMurtry et al., 1990a) with no supplemental fertilization (McMurtry et
al., 1990a).
● Sand Suitability and Substrate Mechanics: Sewilam et al., (2022) assert that “sand
suitability” remains an open question due to scarce literature, specifically citing the
difficulty of “suitable sand for crops that require cooler climates” as a system
limitation. Contrary to this, McMurtry et al., (1990a) provided comprehensive
technical specifications for the optimal growing medium, identifying “builder’s grade
sand” (99.25% quartz, 0.75% clay) with a specific particle size distribution dominated
by: medium sand (0.50–0.25 mm) at 21.0%, coarse (1.00–0.50 mm) at 38.3%, and
very coarse (2.00–1.00 mm) (33.3%) fractions. This granulometry was engineered to
optimize biofiltration and hydraulic conductivity. Longitudinal data confirmed that
clogging was “never observed” over three years of operation, and percolation rates
remained stable without channeling or anaerobic zones (McMurtry et al., 1990a).
Thus, the parameters for sand suitability are well-established in the literature. The
literature demonstrated that for optimal fish health and growth in the recirculating
system utilizing hybrid tilapia (Oreochromis mossambicus x O. niloticus), water
temperatures were kept above 25°C through the use of thermostatic aquaria heaters
(McMurtry et al., 1990b; McMurtry et al., 1997a). Tilapia species (such as
Oreochromis niloticus and hybrids) are classified as warm-water species (Diver, 2000;
Abdelrahman, 2018) that are favored for tropical and sub-tropical regions
(Abdelrahman, 2018) and inherently define the operating environment of the iAVs
(McMurtry et al., 1994). Consequently, the system is inherently optimized for
environments excluding those that necessitate specialized substrates tailored for
maximizing crop production in ambient ‘cooler climates,’ rendering this specific
concern redundant within the typical iAVs framework.
● Economic Viability: The accompanying projected economic returns analysis
(McMurtry et al., 1997b), based on experimental results and current local market
values (McMurtry et al., 1997b), established that the gross returns from this co-culture
system… are on a par with traditional commercial greenhouse tomato production
(McMurtry et al., 1997b). Specifically, the research projected that the annualized
gross returns for the tilapia component alone were estimated to range from $110 to
143/m3 per year (McMurtry et al., 1997b). The projected annual gross returns for the
tomato crop ranged from $50 to 102/m2 (McMurtry et al., 1997b). This comparison
indicated that the overall system’s economic viability was comparable to commercial
greenhouse operations, which Mickey et al., (1989) estimated to range from $77 to
$157/m² annually (McMurtry et al., 1997b).
● Nutrient Dynamics: Sewilam et al., (2022) suggest a lack of data on crop
performance in sand systems. However, McMurtry et al., (1993) provided a detailed
analysis of mineral nutrient concentration and uptake (McMurtry et al., 1993a). The
findings established that despite low absolute concentrations of dissolved nutrients
(e.g., N, P, K, Mg), crop growth was maintained through the constant replenishment
characteristic of the recirculating design (McMurtry et al., 1993a). The research also
demonstrated that the percentage of total nutrient inputs assimilated by the plants
increased in direct correlation with the Biofilter Volume (BFV) ratio (McMurtry et al.,
1993a, 1993b).
● System Optimization: Sewilam et al., (2022) assert that “many questions regarding
optimization” exist due to a lack of literature. Contrary to this, McMurtry et al.,
provided the foundational framework for optimization, characterizing it not as a
missing dataset but as a dynamic interaction between four established variables: feed
input rate, standing fish biomass, system water volume, and biofilter volume.
McMurtry et al., (1997a) evaluated specific biofilter-to-tank ratios (0.67:1 to 2.25:1),
demonstrating that the “optimum” ratio is context-dependent and determined by
specific regional goals, such as prioritizing maximum fish yield versus water
efficiency. The literature further details operational optimization strategies, including
the regulation of ammoniacal-N via feed adjustments (McMurtry et al., 1990a), the
necessity of continuous multi-cropping to maintain pH stability, and specific feed
reformulations to align nutrient input with plant assimilation rates (McMurtry et al.,
1993a).
● Water Efficiency: McMurtry et al., (1997b) quantified the water use efficiency of the
system (McMurtry et al., 1997b). The daily water replacement rate (makeup water)
ranged from 1.2% to 4.7% of the total system volume (McMurtry et al., 1997b).
Beyond exchange rates, McMurtry et al., (1997b) quantified total food production
efficiency (fish plus fruit) at 24.1 g/L of water consumed. This metric compares
favorably to advanced traveling trickle irrigation (23.9 g/L) and dramatically
outperforms traditional methods such as Egyptian tomato production (1.19 g/L)
(McMurtry et al., 1997b). This data directly addresses the functionality metrics
Sewilam et al., claim are missing.
3.2. Historical Context and Citation Record
The work conducted at North Carolina State University (NCSU) on the Integrated
Aqua-Vegeculture System (iAVs), is widely recognized as foundational to the field of
aquaponics (Abdelrahman, 2018; Diver, 2000; Marklin et al., 2013; Dutta et al., 2018;
Ramsundar, 2015). Historical analyses identify this research as a primary source of scientific
data on integrated fish/vegetable production between the late 1970s and 2000 (Martin, 2017;
Greenfeld et al., 2019). The continued relevance and recognition of the NCSU model is
evident in subsequent academic literature, as attested by numerous publications, which
reference the iAVs model’s introduction of the first closed-loop aquaponic system (Marklin et
al., 2013: Dutta et al., 2018; Martin, 2017; Greenfeld et al., 2019; Gott, 2019;
Abdelrahman, 2018; Moldovan et al., 2015; Ramsundar, 2015).
The assertion that literature is sparse is not supported by the widespread citation of
McMurtry’s work in subsequent bio-engineering and aquaculture studies. These citations
confirm that the scientific community has long recognized the iAVs methodology as a
distinct, well-characterized system. Consequently, the “research gap” identified by Sewilam
et al., (2022) does not reflect an absence of scientific inquiry but rather the exclusion of the
primary literature governing iAVs.
3.3. Consequential Methodological Divergence
The omission of the foundational literature resulted in significant methodological divergences
that likely constrained the system’s performance in the Sewilam et al., (2022) study.
Specifically, Sewilam et al., utilized irrigation drip lines with diaphragm emitters and limited
water recirculation to two cycles per day. This contrasts fundamentally with the established
Reciprocating Biofilter (RBF) technique detailed by McMurtry (1990b, 1997a), which
utilizes flood-and-drain mechanics with high-frequency exchanges (5 to 8 times daily).
McMurtry (1993a, 1997a) demonstrated that high-frequency irrigation is critical for the
“constant replenishment” of nutrients, allowing crops to thrive on low concentrations.
Furthermore, the RBF method was shown to reduce Total Ammoniacal Nitrogen (TAN) and
nitrite concentrations by approximately 50% per cycle (McMurtry et al., 1990b, 1997a). By
reducing the daily water processing volume by 50% to 85% relative to McMurtry’s
parameters (McMurtry et al., 1997b), the methodology employed by Sewilam et al.,
represents a sub-optimal configuration that likely underreported the potential efficiency of the
system. - Attribution of System Limitations
Sewilam et al., (2022) identify specific system limitations, including “crop nutritional
deficiencies due to insufficient fertilizers” and a requirement for “specialized training.”
Regarding nutrition, the authors cite Makokha et al., (2020), who investigated an inorganic,
fertigated sandponics system. Attributing limitations characteristic of synthetic formulations
to the Integrated Aqua-Vegeculture System (iAVs) contradicts the system’s documented
biological dynamics.
Robust data confirm that iAVs operates via strategic design (McMurtry et al., 1993b; 1997a)
rather than passive reliance on inputs (McMurtry et al., 1997b). This methodology involves:
(1) optimizing biofilter-to-tank ratios to maximize nutrient extraction and reduce TAN
concentrations (McMurtry et al., 1993b, 1997a); (2) balancing nutrient loads by regulating
feed input to ensure sufficiency (McMurtry et al., 1990a, 1993a); and (3) utilizing targeted
mineral amendments to address specific imbalances (McMurtry et al., 1993a). Therefore,
applying the limitations of an inorganic methodology to iAVs constitutes a critical
misattribution.
Furthermore, the assertion that iAVs necessitates “specialized training” is demonstrably
contradicted by the fundamental design objectives detailed in the literature. McMurtry et al.,
(1990a; 1997b) explicitly optimized the system for “functional simplicity” and “easy to
maintain and operate” (McMurtry et al., 1997a). This operational ease is achieved through
three mechanisms: - Component Integration: The sand beds function simultaneously as biofilters, as
substrate for vegetable growth, and as location for decomposition of waste solids,
reducing mechanical complexity (McMurtry et al., 1997a, 1997b). - Self-Regulating Chemistry: Unlike systems requiring base addition, iAVs
demonstrates pH stability (~6.0) derived from the biological balance between
nitrification (acidifying) and plant nitrate assimilation (alkalizing). This stability is
supported by established physiological principles: the uptake of nitrate (NO3− )
anions by plant roots stimulates the release of hydroxyl (OH− ) or bicarbonate
(HCO3−) ions (Marschner, 1995; Kirkby & Hughes, 1970), which effectively
counteracts the acidity generated by microbial nitrification (McMurtry et al., 1990b;
1997a). Furthermore, the simultaneous availability of ammonium (NH4+ ) and nitrate
(NO3− ) buffers the pH fluctuations typically associated with single-source nitrogen
uptake (Haynes & Goh, 1978; McMurtry et al., 1990a), significantly reducing the
need for external chemical management. - Uniform Distribution: Reciprocating flood-and-drain cycles ensure uniform
distribution of nutrient-laden water within the filtration medium during the flood
cycle and improved aeration through complete atmosphere exchange with each
dewatering (McMurtry et al., 1990a, 1990b, 1994, 1997a). This system feature allows
vegetables to be grown using “traditional methods excluding any which would be
harmful to either the fish or biofilter microbes” (McMurtry et al., 1994) rather than
complex hydroponic protocols (McMurtry et al., 1994). The simplicity of operation
(McMurtry et al., 1994) and the resulting maintenance of adequate nutrient levels
limit or eliminate the need for fertilizer additions (McMurtry et al., 1997a). McMurtry
et al., (1990a) provided a spatial analysis of nutrient distribution within the substrate
(McMurtry et al., 1990a), documenting that nutrient concentrations in the sand
medium generally increased nearest the irrigation furrow (within 50 mm or 1.97 in.)
and toward the bed surface (McMurtry et al., 1990a). The accumulation near the
furrow was linked to the fact that apparent cation exchange capacity (CEC) changes
were greatest near the furrows (McMurtry et al., 1987, 1990a). This change was
attributed to organic matter accumulating on the surface in these areas (McMurtry et
al., 1987, 1990a).
Consequently, the literature describes a system intended for high labor efficiency and ease of
operation, directly refuting the claim that specialized technical training is an inherent
requirement. - Conclusion
Sewilam et al., (2022) conducted an investigation utilizing the functional architecture of the
Integrated Aqua-Vegeculture System (iAVs) – specifically, the biological filtration of
aquaculture effluent through sand beds – but failed to recognize the methodology’s historical
context. This fundamental conflation of iAVs with “Sandponics” (a chemically fertigated
system) led the authors to identify research gaps regarding optimization, sand suitability, and
nutritional limitations that had already been exhaustively quantified and resolved by
McMurtry et al., in the 1980s and 1990s.
The objective of this commentary is not merely to correct nomenclature, but to ensure that the
robust, quantitative data existing on iAVs system performance is preserved for future
research. The foundational literature provides proven metrics for biofiltration efficiency,
water conservation, and economic viability for the advancement of resource-efficient
agriculture in arid regions. Future studies must correctly identify and cite the iAVs
methodology to build upon, rather than replicate, this established scientific record.
Citations
Abdelrahman, M. A. (2018). Effect of Feeding Frequency and Stocking Density on Tilapia
Oreochromis Niloticus and Lettuce Lactuca Sativa Production in Aquaponics System under
the UAE Condition and Business Enterprise Analysis.
Baba, M., & Ikeguchi, N. (2015). Industrial Cultivation Using the Latest Sandponics System.
SEI Technical Review, 80, 104-108.
Diver, S., & Rinehart, L. (2000). Aquaponics-Integration of hydroponics with aquaculture.
ATTRA – National Sustainable Agriculture Information Service.
Dutta, A., et al., (2018). IoT based aquaponics monitoring system. 1st KEC Conference
Proceedings, Vol. 1.
Gott, J. (2019). Practicing ecologies: aquaponics and intervention in the Anthropocene. Diss.
University of Southampton.
Greenfeld, A., et al., (2019). Economically viable aquaponics? Identifying the gap between
potential and current uncertainties. Reviews in Aquaculture, 11(3), 848-862.
Kanazawa, S., Matsuo, K., Baba, M., Misu, H., & Ikeguchi, N. (2017). High Quality
Agricultural Production Support System by Smart Sand Culture Device New Sandponics. SEI
Technical Review, 84.
Kirkby, E.A. and A.D. Hughes. 1970. Some aspects of ammonium and nitrate in plant
metabolism, pp. 69-77. In: E.A. Kirkby: Nitrogen Nutrition of the Plant., Univ. of Leeds,
England.
Makokha, P., et al., (2020). Comparative analysis for producing sweetpotato pre-basic seed
using sandponics and conventional systems. Journal of Crop Improvement, 34(1), 84-102.
Marklin Jr, R. W., et al., (2013). Aquaponics: A sustainable food production system that
provides research projects for undergraduate engineering students. Proceedings of the 2013
American Society for Engineering Education Annual Conference.
Marschner, H. 1995. Mineral Nutrition of Higher Plants. Second ed. Academic Press, San
Diego, California. Meade, T.L. 1974. The Technology of Closed System Culture of
Salmonids. Marine Technical Report 30, University of Rhode Island, Kingston, Rhode Island.
Martín, D. A. (2017). Technical and economical study of Aquaponics feasibility in northern
Finland. MS thesis.
McMurtry, M. R., et al., (1990a). Sand culture of vegetables using recirculated aquacultural
effluents. Applied Agricultural Research, 5(4), 280-284.
McMurtry, M. R. (1990b). Performance of an integrated aquaculture-olericulture system as
influenced by component ratio. North Carolina State University.
McMurtry, M. R., et al., (1993a). Mineral nutrient concentration and uptake by tomato
irrigated with recirculating aquaculture water as influenced by quantity of fish waste products
supplied. Journal of Plant Nutrition, 16(3), 407-419.
McMurtry, M. R., et al., (1993b). Yield of tomato irrigated with recirculating aquacultural
water. Journal of Production Agriculture, 6(3), 428-432.
McMurtry, M. R., Sanders, D. C., Cure, J. D., & Hodson, R. G. (1997a). Effects of
biofilter/culture tank volume ratios on productivity of a recirculating fish/vegetable co-culture
system. Journal of Applied Aquaculture, 7(4), 33-51.
McMurtry, M. R., et al., (1997b). Efficiency of water use of an integrated fish/vegetable
co‐culture system. Journal of the World Aquaculture Society, 28(4), 420-428.
Mickey, S., E. Estes and J. Schultheis. 1989. Greenhouse spring tomato production estimated
net returns, investment cost, and production expenses for a commercial operation in 1990.
Presented at the annual meeting of the N.C. Greenhouse Vegetable Growers Association,
Greensboro, North Carolina, USA.
Moldovan, I. A., & Băla, M. (2015). Analysis of aquaponic organic hydroponics from the
perspective of setting costs and of maintenance on substratum and floating shelves systems.
Journal of Horticulture, Forestry and Biotechnology, 19(1), 73-76.
Noggle, G.R. and G.J. Fritz. 1983. Introductory Plant Physiology, 2nd edition. Prentice-Hall,
Inc., Englewood Cliffs, NJ. 627 p.
Ramsundar, R. (2015). Fishing For a Sustainable Future: Aquaponics as a Method of Food
Production.
Riley, D., and S.A. Barber. 1971. Effect of ammonium and nitrate fertilization on phosphorus
uptake as related to root-induced pH changes at the root-soil interface. Soil Sci. Am. Proc.
35: 301-306.
Sewilam, H., Kimera, F., Nasr, P., & Dawood, M. (2022). A sandponics comparative study
investigating different sand media based integrated aqua vegeculture systems using
desalinated water. Scientific Reports, 12(1), 11093.
Download Full PDF: Addressing the Conflation of Sandponics