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The Pharma Innovation Journal 2022; SP-11(6): 2663-2675
ISSN (E): 2277-7695
ISSN (P): 2349-8242
NAAS Rating: 5.23
TPI 2022; SP-11(6): 2663-2675
© 2022 TPI
www.thepharmajournal.com
Received: 26-04-2022
Accepted: 30-05-2022
Yasir Hanif Mir
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Shakeel Mir
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Mumtaz A Ganie
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Aanisa Manzoor Shah
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Uzma Majeed
Division of Statistics and Agricultural
Economics, SKUAST-Kashmir,
Jammu and Kashmir, India
MH Chesti
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Mehvish Mansoor
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Insha Irshad
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Ayman Javed
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Shazia Sadiq
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Fehim Jeelani Wani
Division of Statistics and Agricultural
Economics, SKUAST-Kashmir,
Jammu and Kashmir, India
Corresponding Author
Yasir Hanif Mir
Division of Soil Science and
Agricultural Chemistry, SKUAST-
Kashmir, Jammu and Kashmir, India
Soilless farming: An innovative sustainable approach in
agriculture
Yasir Hanif Mir, Shakeel Mir, Mumtaz A Ganie, Aanisa Manzoor Shah,
Uzma Majeed, MH Chesti, Mehvish Mansoor, Insha Irshad, Ayman
Javed, Shazia Sadiq and Fehim Jeelani Wani
Abstract
The exploding population has aided to the exhaustion of land and water resources which eventually has
impacted their availability and also causes degradation of such crucial natural resources, which poses a
major threat to the ecological balance and sustainability. In addition, the world population is expected to
touch the mark of 9.8 billion by 2050 with simultaneous alarming reduction, deterioration of farming
land and loss of fertile soils owing to industrialization, urbanization and climate change scenario, which
is a major concern regarding global food security. Moreover, conventional agriculture is facing major
challenges of biotic and abiotic stresses that hamper the crop production and hence cause economic loss.
Therefore, it becomes necessary to develop novel technologies coupled with advanced production
techniques to overcome the present scenario and to secure the future. This review focuses on the soilless
farming which could be adopted to address the aforementioned challenges. The different techniques used
in soilless farming are hydroponics, aeroponics, aquaponics and various solid media cultures, provided
with nutrient rich solution. Soil less farming has high yielding, high nutritional values and economically
feasible which could serve as a measure to overcome the threat of global food security, malnutrition
concern and also in economically uplifting of the farming community.
Keywords: Aeroponics, aquaponics, climate change, food security, hydroponics, soilless farming
Introduction
Soil is by far the primary medium supporting crop growth because of its moisture and nutrition
capacity, along with its ability to perform as a buffer in the instance of an abrupt shift in soil
pH (Ellis et al., 1974) [34]. It provides support, essential nutrients, water, aeration etc. necessary
for plant growth. However, soil has some limitations of biotic (disease, pests) and abiotic
(drought, salinity, nutrient deficiency, soil pollution, poor water quality etc.) stresses which
hamper the crop production. In addition, soil fertility and productivity has been significantly
declined coupled with reduction in the available land per person (Lal, 2015; Lehman et al.,
2015) [68, 70]. One of the major challenges today is to develop a sustainable food system and
eradicate poverty and hunger. However, the provision of food to future generation in a
sustainable manner is a substantial concern, especially for increasing population (Alexandratrs
and Bruinsma, 2012) [3]. According to reports, the future population is anticipated to touch the
mark of 9.8 billion by 2050 with major share of developing nations (Cohen, 2002; UN, 2011)
[25, 120]. Therefore, an incremental food production of about 60-70% will be required to feed
this population in a proper manner, globally (Foote, 2015) [41], however, there is no land
availability for cultivation (FAO, 2020) [36], hence, rising issues must be addressed. The
dramatic growth in population has led to ecological deterioration, resource depletion, uneven
distribution of food, and numerous occurrences of undernourishment. An outcome of a survey
has revealed that there were 820 million undernourished people in various regions of the
world, which could worsen in future if the current circumstances continue to prevail. On the
other side, the farming land is shrinking at an alarming rate due to industrialization and
urbanization and the fertile soil are also at stake because of degradation and climate change
scenario. In India, according to an agricultural census 2015-16, the average farm size was 2 ha
in 1976-77 which has reduced to 1.08 in 2015-16, clearly indicating that the farm land will be
less than a hectare in coming years. Furthermore, the arable land in Jammu and Kashmir has
shrunk from 0.14 ha per person in 1981 to 0.06 ha per person in 2012. Kashmir had a net of 4,
67,700 ha of agricultural land in 2015, which has dropped to 3, 89, 000 ha in 2019, with pulse
production declining from 14,600 ha to 12,767 ha from 2015-2019, and area under maize
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cultivation decreased by 20% between 2003-2012 owing to
land use changes. The Kashmir valley lost approximately 22,
000 ha of paddy land from 1996-2012. On an annual estimate,
Kashmir loses an average of 1375 ha of agricultural land
(Jammu and Kashmir Economic Survey Report, 2017-18) [58].
The number of mega cities is increasing rapidly and migration
from rural to urban areas is also increasing, with current
residence of 56% of world population in cities (Shackleton et
al., 2009) [104]. The soil is not usually available in
metropolitan areas, or there is a paucity of healthy land
attributed to unsuitable geographic or topographic aspects,
along with intensive road and building construction, and if
there is, then it may hold contaminants that are not beneficial
to plants. Climate change is another factor contributing to the
increased ecological, economical, and social issues across the
globe (Eileen, 2009) [33]. The increased temperature, irregular
distribution of rainfall (Bisbis and Gruda, 2018; Gruda et al.,
2019) [17, 48], suggesting that these climatic changes can
negatively influence natural resource availability (fertile land
and water) and poses threats to human health and
sustainability (Bisbis and Gruda, 2018; IPCC, 2007) [17, 56].
Several undeveloped nations in tropical areas are susceptible
to climate change owing to their heavy reliance on rain-fed
farming, economic stagnation, and restricted access to
technological innovations and advanced agricultural
approaches (Dowuona et al., 2014) [32]. Under such
circumstances, researchers must develop novel technologies
and provide the solution and therefore, such technologies
must be adopted in order to withstand the aforementioned
challenges. One of the emerging and promising techniques
among the latest technologies to overcome the current threats
is soilless farming. It is a revolutionary innovation in the field
of agriculture and the appropriate strategy for a continual
delivery of high quantity and quality produce (Sardare and
Admane, 2016) [100]. Soilless farming is a technique of crop
production without soil or within solid media culture or water
culture, where nutrients are provided artificially to the plants
for their growth and development. The different types of
stresses (biotic and abiotic) could also be managed in soilless
farming since it is a controlled system. This approach has
various socio-economic advantages, along with the capacity
to deal with rising global food challenges, malnutrition,
efficient utilization and management of natural resources,
hence conserve ecological sustainability with continuous year
round provision of enough and hygienic food supply. It is a
truly excellent crop growing approach for all nations with
limited farmland, constant changing climate, and escalating
food challenges with indigenous population (Sardare and
Admane, 2013) [101]. Several soilless methods had been
adopted to cultivate the plants in a controlled environment.
Although, soilless farming technology mainly focuses on
hydroponics, aeroponics, aquaponics and solid media cultures
(Texier, 2013) [115] and in this regard they will be discussed
separately in the following sections in detail. There are
various crops grown in soilless cultures including cereals,
vegetables, fruits, condiments, flowers, medicinal crops and
fodder crops (Sharma et al., 2018) [105]. The crops cultivated
in soilless medium has enhanced yielding and nutritional
values (Balashova et al., 2019; Sankhalkar et al., 2019; Singh
et al., 2019; Nicola et al., 2020; Majid et al., 2021) [11, 99, 109, 84,
75] which could serve as a measure to overcome the threat of
global food security and malnutrition concern. The developed
nations are working to improve the efficiency and increase the
production; however, this is still in infancy in developing
nations to be adopted by the farmers since it requires technical
knowhow to operate the system.
Historical evolution of soilless farming
Soilless farming has a prolonged history dating back to
ancient civilizations; however, adequate information has not
been documented for various reasons. There are numerous
prime examples, including Aztecs and Egyptian
hieroglyphics, as well as the hanging garden of Babylon,
which reveals that soilless farming was followed in many past
civilizations. Sir Francis Bacon pioneered the practice of
growing plants without soil in his book Sylva Sylvarum in
1627. John Woodward proposed a more comprehensive
publication concerning water culture in 1699. He was a fellow
of the Royal Society of England, and concluded that the
plants/vegetables cultivated in less pure water grew better
than those planted in distilled water, which he ascribed to
certain minerals in water derived from soil. As a result, this
soil-water mixture became the first man-made hydroponic
nutrient solution (Waiba et al., 2019) [124]. His research was
afterwards followed by the majority of European plant
physiologists in order to build various grounds. They proved
that plant roots absorb water and nutrients, transferring
through the stem and water escapes into the atmosphere via
leaves and draws carbon dioxide from the air. However, until
the contemporary theories of chemistry made substantial
advances in 17th and 18th centuries, precise knowledge of what
exactly plants take up was ambiguous. Therefore, following
the advancement, remarkable breakthroughs were
accomplished in laboratory studies of plant physiology and
nutrition between 1800s and 1920s. Later during 1937,
Professor William Frederick Gericke coined the term
“hydroponics” to describe crop cultivation with roots
immersed in nutrient rich solution. In 1940, he authored
“Complete Guide to Soilless Gardening” and despite its
limitation of being concerned with water only, his wok is
considered the foundation for all forms of hydroponic
growing. Furthermore, the nutrient solution known as
Hoagland solution, which is being used in the current era, was
developed by two plant nutritionists named Dennis R.
Hoagland and Daniel I. Arnon at the University of California.
Since science progressed, more novel and sophisticated
approaches were developed, and one among the additions to
soilless farming was the use of growth medium with
alternately flooding and draining of an optimal amount of
both nutrients and air, which was pioneered by Robert B. and
Alice P. Withrow. The practice of cultivation without soil
(hydroponically grown vegetables) was also used to feed the
passengers on a ship sailing in Pacific Ocean during 1930.
Furthermore, in 1945, the United States Air force established
one of the largest hydroponic farms on the Island of Hawaii.
In India, W. J. Shalto Duglas, an English scientist, introduced
the hydroponic technique followed by an establishment of a
laboratory in West Bengal and authoring a book named
“Hydroponics-The Bengal System”. As soilless cultivation
gained popularity due to increased scientific acceptance
coupled with technological advancement, commercial farms
were established in numerous countries between 1960-70,
including Abu Dhabi, Arizona, Belgium, California,
Denmark, German, Holland, Iran, Italy, Japan, Russian
Federation and others (Sardare and Admane, 2013) [101]. This
includes the establishment of various computerized and self-
automated hydroponics farms around the globe, as well as the
widespread availability of hydroponic kits. NASA has
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conducted substantial hydroponic research in Arizona, Euro
fresh Farms in Willcox for their Controlled Ecological Life
Support System to grow plants for space (Gruda, 2009;
Savvas and Passam, 2002) [47, 103]. Arizona farm produced
more than 200 million pounds of tomatoes hydroponically
(Javaid, 2020) [59] with complete absence of pesticide
residues. In Canada, hundreds of acres of land are dedicated
to commercial hydroponic greenhouses that produce
tomatoes, peppers cucumbers and a variety of other
vegetables (Waiba et al., 2019) [124]. Presently, many
commercial firms have created AI-supported software to
monitor and control the hydroponic system through mobile
phones via the internet or Bluetooth facility (Lakshmanan et
al., 2020) [67].
Types of Soilless Farming
Soilless farming is an approach of cultivating plants in
nutrient-rich solution using an artificial medium such as sand,
gravel, rock wool, peat moss, sawdust, coconut fiber,
vermiculite, perlite and so on to provide physical support for
root growth. Several innovations have emerged and attracted
attention in recent years including grow bags, net caps, and a
range of customized nutrient solutions for particular plants.
These cultivation methods were designed to be used in
soilless farming (Gruda and Tanny, 2014) [49]. Soilless
farming is mainly classified into two types viz; open soilless
system and closed soilless system. In brief, both categories
are outlined below:
Open soilless cultivation
In this cultivation system, dripping framework is used to
supply the dissolved nutrients to plants required for their
growth and development. In general, this method should have
a run-off designated at one end, regulated in the root zone to
ensure optimum uptake of available nutrients by plants. The
nutrient solutions in this system are only used once and are
not re-circulated or recycled. Therefore, one of the primary
benefits of this system is that there won't be any risk of
infection in the plant system owing to regular changes in the
nutrient solution (Jones, 2005) [60]. It is further divided into
following types (Table 1):
Table 1: Types of open soilless cultivation and their description
Type
Description
Root dipping
technique
Pots containing growth media are kept in a container having suitable quantity of nutrient solution. The lower portion of the
pots (1-3 cm) remains in direct contact with the solution (Hayden, 2004) [54] where roots are half submerged in the solution and
partly suspended in the air. This method is mostly adopted for growing small leafy greens (Rousos and Harrison, 1986) [97]. It
was observed that vegetables grown in root dipping hydroponic systems contains excellent iron and calcium levels, and jute
mallow had higher plant height, the number of leaves, stem girth, higher yields, higher fruit weight, fresh weight of stem and
fresh weight of root compared to soil farming systems (Olubanjo et al., 2021) [85].
Floating
technique
In this technique, small pots with Styrofoam sheets are used to fix plants and enable them to float on nutrient solution in
shallow containers of 10 cm depth. The nutrient solution used, is artificially aerated in order to meet the needs of the growing
plants.
Capillary
action
technique
In this technique, various forms and sizes of pots are used having holes at the bottom. These pots are filled with inert media,
and seedlings or seeds are planted before being placed in shallow containers having nutrient solution. Aeration is one of the
significant parameters that influence the overall successful functioning of this system, which could be maintained by utilizing
old coir dust mixed with gravel or sand. The nutrient solution enters the medium by capillary action.
Closed soilless cultivation
In this technique, as the name implies, the nutrients in
solutions are circulated, examined and maintained. Frequent
maintenance of nutrient supplements is required, since
inappropriate inspection can result in loss of equilibrium,
which can lead to plant death. The primary drawback of this
approach is that it is reliant on electricity (Lee and Lee, 2015)
[69]. It includes following types, which are discussed further in
the following subsections:
Hydroponics system
The word Hydroponic is originated from the Greek terms
hydro indicating “water” and ponos denotes “labor/working”,
which was introduced by W. F. Gericke in 1930s. It is one of
the soilless farming techniques where plants are cultivated
using mineral nutrient solutions. These nutrient solutions
contain precise quantities of fertilizers required for a specific
plant (Mok et al., 2014) [80] and inert materials supplied with
nutrient solution are also used for root growth (El-Kazzaz and
El-Kazzaz, 2017; Sardare and Admane, 2016) [35, 100].
Hydroponics has been used effectively to raise a wide range
of crops including lettuce, cucumber, tomato, herbs and many
kinds of flowers (Asao, 2012) [7]. It has several benefits over
traditional cultivating system, including rapid growth, high
productivity, ease of handling, efficient water use (Barbosa et
al., 2015) [14] and reduced fertilizer use (Rana et al., 2011;
Cuba et al., 2015) [94, 27]. In addition, roots do not have to
search for mineral elements, and crops can grow closer
together, leading to increased output from less space (Jones et
al., 1991) [61]. As a result, it is increasingly being adopted by
commercial industries to enhance the production. The nutrient
concentration of solution is managed and monitored to detect
the symptoms and nutrient deficiencies or toxicity in the plant
system (Adrover et al., 2013 and Cuba et al., 2015) [2, 27].
Additionally, this approach has a tendency to eradicate the
soil-borne biotic and abiotic stresses (Harris, 1992) [53].
Therefore, it becomes financially viable and lucrative, while
simultaneously laborious for large areas (Pullano, 2013) [90].
Hydroponics has proven to be extremely beneficial in
toxicological investigations on the buildup of numerous
toxins in plants, in the execution of scientific research on
native and exotic crops for economical or therapeutic uses,
and also in conventional crops such as vegetables and
ornamentals. Therefore, the combination of all the benefits
makes hydroponics system more productive than soil based
cultivation system. The global hydroponic market was of a
value of 9.5 billion USD in 2020 and is anticipated to account
for USD 17.9 billion by 2026, increasing at cumulative annual
growth rate (CAGR) of 11.3% during the forecasting period
(Global Forecast, 2026) [43]. This rise in hydroponic sector can
be ascribed to increased acceptability of controlled
environment agriculture. In India, the hydroponic market is
predicted to grow at a CAGR of 13.53% during the forecast
period (2021-27), clearly depicting that the adoption of
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hydroponics in India is increasing, where fruits, vegetables
and flowers accounts for the majority of the market (DataM
Intelligence Analysis, 2022) [28]. This technique is further
classified as follows (Ali, 2017) [4].
Nutrient film technique (NFT)
NFT is a closed hydroponic system designed by Allan cooper
in England in the 1960s. In this method, dissolved nutrients in
a solution are circulated through the bare roots of plants as
shallow stream of water in a watertight gully, known as
channels. The depth of the circulating flow is quite shallow
not more than a thin film of water, ensuring the root mat
developed at the bottom of channel receives an appropriate air
exposure. A thin layer develops on the roots, from where the
plants acquire required oxygen and nutrients (Morgan, 2009)
[81]. As a result, NFT becomes water and nutrient efficient,
and there are numerous studies evaluating the potential
benefits of this approach. Upon comparison to the protected
soil-based growth system, NFT has proved to be an effective
hydroponic approach that provided nutritionally improved and
greater harvests (Majid et al., 2021) [75]. Recently, this system
has been modified with various supporting medium and
growing techniques, with lettuce being the most common
cultivated crop using NFT.
Wick system
Wick system is the basic form of hydroponic system;
traditionally contains no mobile parts and does not require
electricity nor uses water circulation pump (Shrestha and
Dunn, 2013) [107]. Hence, there is no recirculation of nutrient
solution instead the plants absorbs solution via capillary
action of the roots and fibres (Ferrarezi and Testezlaf, 2016)
[40]. As a result, it can be quite useful in areas with negligible
or no assess to electricity. The wick is a component,
connecting the potted plants and nutrition, aiding in the
circulation of nutrient solution to the root zone. An outcome
of a study has revealed a significant effect of this system on
plant height, leaf number, leaf area, dry weight, harvest index
and fresh weight in Brassica chinensis L. (Harahap et al.,
2020) [52]. However, it is not suggested for long-term
cultivation (Lee and Lee, 2015) [69].
Water culture or deep-water culture (DWC)
In this technique of hydroponics, seedlings are immersed in
nutrient rich, fresh water, and plants acquire the required
nutrition for their growth and development. Rectangular
containers of 10-20 cm depth filled with nutrient solution are
used, containing seedlings hovering in panels on the surface
(Van et al., 2002) [121]. Hence, it is often referred as deep flow
technique, floating raft technology or raceway. It is generally
used to grow short-term, leafy greens and herbs. The
oxygenation is achieved through the use of an air stone
connected to an air pump, which generates bubbles and
oxygenates the surrounding water, and (or) by using
appropriate amounts of hydrogen peroxide (H2O2). In order to
optimize growth, the concentration of oxygen, conductance,
and pH must be maintained (Jones, 2005) [60], as plants grow
& utilize resources, the pH and EC of the water fluctuates.
Therefore, regular surveillance is required since nutrient
availability to plants would be impeded if the pH is too high
or low. Lettuce, Chinese cabbage, spinach, and other
vegetables are commonly cultivated in this framework.
Ebb and Flow systems
This method is comparable to the trickle system utilizing an
identical set of containers. Ebb and Flow are two tide phases,
with Ebb being the exiting period when water drains and Flow
being the entering period when water rises again. The pots
contain an inert material that acts as a transitory reservoir of
water and aqueous mineral nutrients. A pump is used to flood
the system periodically with nutrient solution for a brief
period of time (5 to 10 minutes), submerging the roots before
turning off the pump to allow the system to drain. This result
in the provision of the nutrients to plants and the solution is
re-circulated. The rate of flooding the system depends on the
medium’s water retentive capacity. The highly retention
media require only one flooding a day, whereas others
necessitate 2 to 6 flooding per day, with every “flood” round
lasting merely few minutes. Therefore, the quality of medium
determines the plant growth and success of this system. All
sorts of vegetables can be grown and is also appropriate for
crops with enormous root balls (Halveland, 2020) [51].
Drip hydroponic system
In this approach, the system is built using two containers, one
at the top and another at the bottom, with vegetables grown in
the top container and nutrient solution kept in the bottom
container. As the name implies, it uses small emitters to
deliver the solution directly to the plants. The water is
pumped from the reservoir via main line, and further divided
into lateral lines that run directly alongside plants. Hence, it is
also called trickle or micro irrigation system. Oxygenation of
water is achieved by using an aquarium stone (El-Kazzaz and
El-Kazzaz, 2017) [35]. There are two types of drip system such
as recirculating or recovery system and non-recovery or non-
circulating system. When water is delivered to the artificial
medium, the roots do not absorb all of it. Therefore, the
excess water in recovery method is permitted to drain back
into the tank, but excess water in the non-recovery system is
permitted to run off as waste. Although drip systems are
relatively conservative, the magnitude of wastage is generally
small, making it very appealing to commercial growers since
it requires minimal reservoir management. Conclusively, a
drip system is a diverse and practical approach of
hydroponics. It is appropriate for wide range of plants and
herbs and provides greater regulation of water and fertilizer
delivery. Different types of hydroponic systems are
graphically presented in figure 1.
Considering the importance of hydroponic systems in modern
agriculture, numerous studies have been conducted to
evaluate its potential and beneficial impacts to feed the future
population globally (Table 2). Hence, it becomes essential for
researchers to put forward high-tech innovations and farmers
to adopt in order to enhance the output and minimize the
influence of various natural and anthropogenic activities to
preserve the ecological balance, which would eventually serve
and uplift the universal goal of sustainability.
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Fig 1: Different types of Hydroponic system
Table 2: Scientific studies concerning hydroponic system as a potential alternative to conventional cultivation system
S.
No.
Paper Title
Country
Parameters Studied
Author
1.
Prediction and comparative analysis using ensemble classifier
model on leafy vegetable growth rates in DWC and NFT smart
hydroponic system
India
Plant growth dynamics
Srivani et al.,
2022 [112]
2.
Development of greenhouse with root dipping technique
hydroponics structure to test the performance of jute mallow
Nigeria
Plant height, stem girth, leaf number, and
yield.
Olubanjo et al.,
2021 [85]
3.
Controlled comparisons between soil and hydroponic systems
reveal increased water use efficiency and higher lycopene and β-
carotene contents in hydroponically grown tomatoes
UK
Water consumption, WUE, PWU, water
transpired, stem growth, fresh weight, dry
weight, fruit yield, lycopene, β-carotene,
TSS, TAA
Verdoliva et
al., 2021 [122]
4.
Strategies for improved yield and water use efficiency of lettuce
(Lactuca sativa L.) through simplified soilless cultivation under
semi-arid climate
Brazil and
Myanmar
Yield, leaf number, WUE, stomatal
conductance
Nicola et al.,
2020 [84]
5.
Growth and yield response of Okra under root dipping
hydroponic and conventional farming system
Nigeria
Plant height, stem girth, leaf number, root
weight, and yield.
Olubanjo et
al., 2020 [85]
6.
Growth, production and water consumption of coriander grown
under different recirculation intervals and nutrient solution depths
in hydroponic channels
Brazil
Plant height, shoot fresh and dry matters,
water consumption, WUE and visual
quality
Silva et al.,
2020 [108]
7.
Evaluation of hydroponic systems for the cultivation of lettuce
(Lactuca sativa L., var. Longifolia) and comparison with the
protected soil based cultivation
India
Crop duration, photosynthetic parameters,
crop growth parameters, crop quality para
meters, Water consumption, economy
Majid et al.,
2021 [75]
8.
Evaluation of tropical tomato for growth, yield, nutrient and water
use efficiency in recirculating hydroponic system
Ghana
WUE, NUE, plant growth, dry matter, fruit
yield and quality
Ayarna et al.,
2020 [9]
9.
Tomato production through vine cutting technology in
hydroponics system
Nigeria
Shoot formation, number of fruits, fruit
weight
Ossai et al.,
2020 [87]
10.
Evaluation of hydroponic cultivation techniques as a supplement
to conventional methods of farming
India
Germination rate, plant vigour, root
morpho-anatomy, pigment contents, yield
Gurung
et al., 2019 [50]
Aeroponics
The word “aeroponics” is originated from the Greek terms aer
(air) and ponos (labour). Plants are cultivated inside an air or
mist atmosphere without using any aggregate medium,
however, an assistance of artificial support is used to sustain
the plant growth (figure 2) (Osvald et al., 2001) [88]. As a
result, it varies from both conventional hydroponics and
aquaponics. The primary notion of aeroponics is to cultivate
plants in a protected atmosphere by delivering a nutrient
solution in a mist or atomized form with the help of nozzles
and foggers (Mbiyu et al., 2012) [78] and a film of nutrient is
formed on the roots from where the roots absorb nutrient for
their growth. The precise character of atomization spray
frequency and duration enables the quantification of nutrient
absorption levels within the plant throughout under various
conditions. Rather than a continuous misting, the atomization
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spray gives an occasional sprinkle of nutrients to plant roots
periodically for a specific duration (Lakhair et al., 2018) [66].
Numerous studies have found that aeroponics is an efficient
plant cultivation technology (Peterson and Krueger, 1988) [89],
requires minimum water while providing an ideal condition
for the growth of plants (Buer et al., 1996) [19]. Aeroponics is
a high-tech kind of hydroponic system that is classed as a
closed system of soilless growing. This is a technique where
plants are supported by plastic or polystyrene panels and
positioned horizontally at the top of the growing container.
These panels are typically comprised of inert substances like
plastic, steel coated with plastic film etc. to suspend the root
system (Maucieri et al., 2019) [76]. The controlled parameters
are equal nutrient levels, EC, pH, temperature, humidity, light
intensity, atomization rate, atomization spray duration,
atomization interval, and availability of oxygen (Lakhair et
al., 2018) [66]. Aeroponics could be a good approach for
growing potato minitubers and it was discovered that limiting
nutrition delivery during the stolon growth stage substantially
boosts activity of root, limits stolon growth, and eventually
triggers tuber initiation (Chang et al., 2012) [22]. Therefore,
nontuberizing conditions including warm conditions and
delayed cultivars promote the employment of nutrient
interruption approach. This system consists of three
frameworks; the first is high pressure, which does not
typically utilize a water pump, following by second known as
“soakaponics”, which is a low-pressure framework using
standard water pumps to pour out the sprinklers (mister
heads). The third framework consists of ultrasonic foggers
that produce a mist (Domingues et al., 2012) [31]. Hence, to
mist the growing roots, various types of nozzles are used such
as ultrasonic atomization foggers, high-pressure atomization
nozzle and pressurized airless nozzles. An automated system
maintains and controls static pressure of 60-90 Psi (Liu et al.,
2018) [72]. The spray span will be between 30-60 seconds;
depending on the type of crop, cultivation period, plant
growth stage and time. Aeroponics has a distinct advantage of
promptly eliminating problematic plants from the support
structure without disturbing or contaminating the neighboring
plants. This approach is mainly suitable for small horticultural
crops and has not been widely employed due to its high
investment and management costs (Rakocy, 2012) [91].
However, the research revealed that crops cultivated in an
aeroponic system have more production and comparable
phenolics, flavonoids, and antioxidant characteristics than
crops cultivated in soil (Chandra et al., 2014) [21]. All herbs
grown in aeroponics had the highest vitamin C content,
whereas Holy Basil and Perilla grown in the substrate had the
highest essential oil concentration (Bohme and Pinker, 2014)
[18]. Aeroponics can outperform regular agriculture in terms of
yield. As a result, it has the ability to generate more revenue
and minimize the cost of producing quality seed, rendering
widely accessible to growers in underdeveloped nations.
NASA has financed exploration and innovation of
sophisticated technologies to optimize aeroponic efficiency
and minimize maintenance costs. This method is utilized as
research tool and is appropriate for studying root morphology.
Aeroponics has also revolutionized plant cloning from
cuttings, since numerous plants were considered difficult to
propagate; sensitive to bacterial infection became easier as it
provides a highly aerated environment surrounding the root,
resulting in good root hair formation. The global market was
worth of $578.70 million in 2018 and is expected to touch
$3.53 billion by 2026, increasing at a CAGR of 25.60%
(Global Opportunity Analysis, 2019) [44]. Therefore, the
global population explosion and spike in acceptance of
controlled agriculture is likely to generate significant
aeroponics market opportunities. Table 3 summarizes some of
the studies that have been conducted in light of the
significance of aeroponics.
Fig 2: Aeroponics plant growing system with computer controlled techniques. (Source: Lakhair et al., 2018) [66]
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Table 3: Scientific studies concerning aeroponic system as a potential sustainable approach to conventional cultivation system
S.
No.
Paper Title
Country
Parameters Studied
Author
1.
Growth and production of potato mini tubers (Solanum
tuberosum L.) in the aeroponic system by root zone
treatment and concentration of leaf-fertilizer
Indonesia
Growth and yield of mini tubers
Lhokitasari et
al., 2022 [71]
2.
A comparative LCA of aeroponic, hydroponic and soil
cultivations of bioactive substance producing plants
Czech
Republic
Content of bioactive substances, caffeine and
theobromine contents, biomass yield, flavonoids
Wimmerova et
al., 2022 [125]
3.
Aeroponic evaluation identifies variation in Indian potato
varieties for root morphology, nitrogen use efficiency
parameters and yield traits
India
Root system architecture, plant height, leaf area, root
and shoot dry weight, tuber traits and NUE parameters
Tiwari et al.,
2022 [116]
4.
The response of different potato cultivars to plant growth
promting rhizobacteria (PGPRs) and chemical fertilizers
in aeroponic culture conditions
Iran
Number and weight of min tuber, number of stolon,
number of days up to tuberization, plant height, length
of stolon
Nasiri et al.,
2022 [82]
5.
Exogenous salicylic acid improves photosynthetic
pigments and morphological traits of four medicinal
plants in an aeroponic system
Iran
Chlorophyll, carotenoid, plant height, root length, root
volume, number of leaves, root fresh weight, root dry
weight, shoot fresh weight, shoot dry weight
Mohit et al.,
2021 [79]
6.
Yield, characterization and possible exploitation of
Cannabis Sativa L. roots grown under aeroponics
cultivation
Italy
Plant growth and root bioactives (β-sitosterol,
stigmasterol, campesterol, friedelin and epi-
friedelanol)
Ferrini et al.,
2021 [38]
7.
Sensor based nutrient recirculation for aeroponic lettuce
cultivation
Republic
of Korea
Nutrient solution requirement and environmental
pollutions
Chowdhury et
al., 2021 [24]
8.
Growth, yield and dormancy of aeroponically produced
potato minitubers as a function of planting density and
harvesting date
Brazil
Growth and yield of potato, effect of harvesting date
and planting densities, number of stem, leaves,
number and fresh weight of mini tubers
Balena et al.,
2021 [12]
9.
Potato production under different soilless systems
Egypt
Plant height, root length, number of leaves, stem
diameter, leaf area, leaf length and potato yield
Khater, 2021
[63]
10.
Comparison of aeroponics and conventional potato mini
tuber production systems at different plant densities
Turkey
Mini tuber production and yield
Çalışkan et al.,
2020 [20]
Aquaponics system
Aquaponics is a type of soilless culture where aquaculture in
integrated with hydroponics for the purpose of producing both
fish and vegetables in a synergistic environment (Rakocy,
2007) [93], where the nutritious fish water is supplied to
hydroponic system and nitrifying bacteria transform ammonia
into nitrates. The closed circulation system leads
accumulation of aquatic effluents, arising from leftover feed
or rearing animals such as fish, which in turn becomes
hazardous to aquatic animals in high proportion; however, it
contains nutrients required for plant growth. Hence, a pump is
utilized to extract the water from the fish tank and deliver to
the plant growing container through a biofilter where
nitrifying bacteria can grow and toxic compounds are broken
down. The beneficial bacteria like Nitrosomonas sp. and
Nitrobacter sp. convert ammonia to nitrites and nitrites are
converted to nitrates through metabolic process, respectively
(Rakocy et al., 2016) [92]. This ammonia conversion is
amongst the significant activities in an aquaponic system
since it minimizes the toxins for fish and permits the
associated nitrate compounds to be assimilated for plant
sustenance. The water is then cleansed and oxygenated before
being returned to the aquaculture section, and the cycle
continues. Many plants are suitable for aquaponics however it
depends on the nutrient requirement of the plants. Green leafy
vegetables having low to moderate nutritional demands thrive
in less fish density and other plants with high nutrient
requirement needs greater fish densities. There are different
types of fishes that can be widely cultivated along with plants
and they are classified as air-breathing and water breathing
fish. Some of the air-breathing fishes are Anabas, Pangasius
and gourami. Water breathing fishes are Tilapia, Red-bellied
natter, rohu, mrigal and catla. Even ornamental fishes can be
grown in an aquaponics system and high yield can be
obtained from both fish and plants (Azad et al., 2016) [10].
This aquaponics system can ensure food security in urban
area by cultivating vegetables where space is not sufficient
and also where scarcity of fertile land, soil degradation, are
and lack of freshwater and problematic soil (Bindraban et al.,
2012; Klinger and Naylor, 2012) [16, 64]. Aquaculture can be
effectively combined with three systems of hydroponics such
as Deep-Water System, Nutrient Film Technique, flood and
drain system, among these different systems DWC and NFT
are the most widely used aquaponics system (Maharana and
Koul, 2011) [74]. India, Israel, China and Africa are the
emerging aquaponic leading nations (Singh and Singh, 2012)
[110]. The global market value of this system valued at $662.49
million in 2019 and is projected to reach a market size of
$1.29 billion in 2026 with a CAGR 12.5% (Global
Aquaponics Market, Forecasts, 2021) [42].
Growing Medium and its types
The solid media culture is a medium other than soil which is
inert and organic or inorganic material to support the plant
growth which can be in different form. The media used must
have high water holding capacity, porosity and various other
properties leading to appropriate nutrition solution supply,
proper oxygenation of roots to keep plants healthy. The
quality of media must be greatly maintained to ensure good
growth of seedlings. Different media is used to cultivate the
plants since these media types has better physical properties
with supplied nutrition to sustain plant growth and enable the
efficient usage of resources. There are various mediums used
such as coco coir, hydroton, perlite, vermiculite, peat moss,
saw dust, rock wool, coarse sand etc. to sustain plant growth
(Farhan et al., 2018, see for review) [73]. These mediums are
versatile in soilless production having excellent moisture and
nutrient holding ability, good aeration, and easy exchange of
oxygen. In addition, vermiculite has abundant amount of
potassium and magnesium and is also rot resistant, helps to
improve soil structure. Furthermore, some of the medium
used are impervious to microbiological degradation, however,
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are far pricey than other material and are not interchangeable
with other insulation material. Therefore, different methods
adopted to use these growing mediums for crop production
are, hanging bag technique, grow bag technique, trough or
trench technique and pot technique. There are numerous
studies confirming the use of growth media influence on plant
growth and nutrition and eventually on the agricultural output.
Some of the studies are mentioned in table 8 concerning the
use of growth media.
Table 4: Scientific studies concerning aquaponic system as an efficient alternative to conventional soil based system.
S.
No.
Paper Title
Country
Parameters Studied
Author
1.
Fish feeds in aquaponics and beyond: A novel concept to
evaluate protein sources in diets for circular multitrophic food
production systems
Germany
Nutrient cycling, circular multitrophic food
production system, nutrient density
Shaw et al., 2022
[106]
2.
Cost benefit analysis of soilless cultivation system in Tagaytay
city, Philippines
Philippines
Cost-benefit analysis
Tality et al.,
2022 [114]
3.
Fish welfare in urban aquaponics: Effects of fertilizer for lettuce
(Lactuca sativa L.) on some physiological stress indicators in
Nile Tilapia (Oreochromis niloticus L.)
Spain
Fish production parameters, physiological
indicators of fish stress and lettuce growth
Villarroel et al.,
2022 [123]
4.
Effect of biofertilizers on the integrated culture of genetically
improved farmed Tilapia and green beans in aquaponics
Malaysia
Effect of commercial biofertilizers on
production efficiency.
Saufie et al.,
2022 [102]
5.
Survival and growth rates of mangroves planted in vertical and
horizontal aquaponic system in north Jakarta, Indonesia
Indonesia
Survival rate, correlation between physico-
chemical environment parameters and
survival and growth rates
Hilmi et al.,
2022 [55]
6.
Complementary nutrients in decoupled aquaponics enhances
Basil performance
USA
Biomass, height, SPAD chlorophyll index,
root:shoot biomass ratio
Rodgers et al.,
2022 [96]
7.
Structural and biophysical properties of whole leaf and root
tissue and isolated cell walls of common green bean and tomato
seedlings grown in an aquaponics system relative to soil-grown
counterpart
USA
Comparing aquaponics and soil-grown
counterpart and evaluate changes in
structural components and energy producing
components
Knoll and Marry,
2022 [65]
8.
Early production of strawberry in aquaponic systems using
commercial hydroponic bands
Spain
Production and quality of strawberry
Fernández-
Cabanás et al.,
2022 [39]
9.
Small-scale aquaponics and hydroponics systems: Pak Choy and
spinach growth rate comparison
Malaysia
Quality, germination time, yield,
Lynn et al., 2022
[73]
10.
Basil, Ocimum basolicum, yield in northern latitudinal aquaponic
growing conditions
USA
Yield
Abbey et al.,
2021 [1]
Table 5: Scientific studies regarding the different growth media used in soilless farming
S.
No.
Paper Title
Country
Parameters studied
Author
1.
Effect of different growing media on growth and yield of leafy
vegetables in nutrient film technique hydroponics system
Nepal
Growth and yield
Chhetri et al., 2022
[23]
2.
The effect of different growing media on physical morphology of
Rockmelon (Cucumis Melo Linn cv. Glamour) seedling
Malaysia
Plant height, number of leaves, total leaf
area and stem girth
Rauf et al., 2022
[95]
3.
Soilless tomato production: Effects of hemp fiber and rock wool
growing media on yield, secondary metabolites, substrate
characteristics and greenhouse gas emissions
Germany
Leaf area, plant height, yields and fruit
quality.
Nerlich et al., 2022
[83]
4.
Non-composted chinaberry (Melia azedarach L.) sawdust mixtures
as growth medium for okra (Abelmoschus esculentus (L.) Moench)
Pakistan
Growth, seed germination, leaf area,
chlorophyll content, plant biomass,
number of pods per plant, dry weight
Yasin et al., 2022
[126]
5.
Conception and development of recycled raw materials (coconut
fiber and bagasse)- based substrates enriched with soil
microorganisms (Arbiscular Mycorrhizal Fungi, Trichoderma spp.
And Pseudomonas spp.) for the soilless cultivation of tomato (S.
lycopersicum)
France
Tomato production, plant performance,
biotic and abiotic stress.
Masquelier et al.,
2022 [77]
6.
Effects of growing substrate, mode of nutrient supply, and saffron
corm size on flowering, growth, photosynthetic competence, and
cormlet formation in hydroponics
Egypt
Flowering traits, growth parameters,
photosynthetic rate and stomatal
conductance, yield
Dewir et al., 2022
[30]
7.
The impact of different growth media and ammonium-nitrate ratio
on yield and nitrate accumulation in lettuce (Lactuca sativa var.
longifolia)
Turkey
NO3- accumulation, yield and growth
attributes
SöYlemez, 2021
[111]
8.
Nursery production of Pinus engelmannii Carr. with substrates
based on fresh sawdust
Mexico
Substrate combinations that favour the
quality of Pinus engelmannii Carr.
González-
Orozco et al., 2018
[46]
9.
Sawdust and bark-based substrates for soilless strawberry
production: irrigation and electrical conductivity management
Canada
Productivity potential
Depardieu et al.,
2016 [29]
10.
Impacts of the substrate medium on tomato yield and fruit quality in
soilless cultivation
Greece
Yield, fruit quality parameters
Tzortzakis and
Economakis, 2008
[119]
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Nutrient solution for the soilless system
The aqueous solution containing nutrients needed for plant
growth and development along with air (oxygen) and water.
Currently, 17 nutrient elements regarded for their essential
growth are carbon, hydrogen, oxygen, nitrogen, phosphorus,
potassium, calcium, magnesium, sulphur, iron, copper, zinc,
manganese, molybdenum, boron, chlorine and nickel
(Salisbury and Ross, 1992) [98]. Elements like Carbon and
Oxygen are obtained from the atmosphere (Trejo-Téllez and
Gómez-Merino, 2012) [117]. The nutrient solution is prepared
by dissolving inorganic salts in water, which dissipates as ions
are absorbed by the plant root system. The level of nutrients
in the solution should be monitored regularly and the best
time is between 6:00 and 8:00 am. The water and nutrient
requirement varies every day based on the type of crop and
age of the plant. This nutrient solution should be applied to
the roots of the plant without wetting the foliage as it causes a
scorching effect on leaves. Regularly around 20-50% of the
nutrient solution in the hydroponic system has to be drained
off and refilled with the new solution as it avoids the
accumulation of toxic ions (Sardare and Admane, 2013) [101].
Table 6 presents the concentration of different nutrients used
in soilless farming. Furthermore, optimum EC and pH for
different crops has also been summarized in table 7.
Table 6: Commercially prefixed available nutrient solution and concentration ranges of essential mineral elements (Cooper, 1988; Steiner, 1966;
Baudoin et al., 1990) [26, 113, 15]
Nutrient
Hoagland and Arnon (1938)
Hewitt (1966)
Cooper (1979)
Steiner (1984)
N
210 mg L-1
168 mg L-1
200-236 mg L-1
168 mg L-1
P
31 mg L-1
41 mg L-1
60 mg L-1
31 mg L-1
K
234 mg L-1
156 mg L-1
300 mg L-1
273 mg L-1
Ca
160 mg L-1
160 mg L-1
170-185 mg L-1
180 mg L-1
Mg
34 mg L-1
36 mg L-1
50 mg L-1
48 mg L-1
S
64 mg L-1
48 mg L-1
68 mg L-1
336 mg L-1
Fe
2.5 mg L-1
2.8 mg L-1
12 mg L-1
2-4 mg L-1
Cu
0.02 mg L-1
0.064 mg L-1
0.1 mg L-1
0.02 mg L-1
Zn
0.05 mg L-1
0.065 mg L-1
0.1 mg L-1
0.11 mg L-1
Mn
0.5 mg L-1
0.54 mg L-1
2.0 mg L-1
0.62 mg L-1
B
0.5 mg L-1
0.54 mg L-1
0.3 mg L-1
0.44 mg L-1
Mo
0.01 mg L-1
0.004 mg L-1
0.2 mg L-1
-
Table 7: The optimum range of EC and pH values for vegetables grown in hydroponics crops (Sharma et al., 2018) [105]
Crops
EC (dSm-1)
pH
Asparagus
1.4-1.8
6.0-6.8
Bean
2.0-4.0
6.0
Broccoli
2.8-3.5
6.0-6.8
Cabbage
2.5-3.0
6.5-7.0
Celery
1.8-2.4
6.5
Cucumber
1.7-2.0
5.0-5.5
Egg Plant
2.5-3.5
6.0
Leek
1.4-1.8
6.5-7.0
Lettuce
1.2-1.8
6.0-7.0
Pak Choi
1.5-2.0
7.0
Peppers
0.8-1.8
5.5-6.0
Parsley
1.8-2.2
6.0-6.5
Spinach
1.8-2.3
6.0-7.0
Tomato
2.0-4.0
6.0-6.5
Advantages and Disadvantages
Soilless farming is a prominent approach in today’s world
with numerous benefits over traditional cultivation system. It
offers favorable environment to plants and provide a year
round production with minimum usage of water and nutrients
compared to conventional agriculture. Numerous studies on
the subject have shown that soilless faming has potential to
produce higher output than soil based cultivation. The
controlled system of soilless farming also reduces biotic and
abiotic stresses, thus sustain crop growth. The conservation of
resources and ecological sustainability is amongst the
profound advantages of soilless farming.
Despite several merits, it also has certain demerits including
technical knowhow requirement to operate the system, higher
initial investment, surveillance of various plant growth
parameters (pH, EC, nutrient concentration etc.), and
electricity requirement. Therefore, careful consideration is
required before initiating soilless cultivation.
Conclusion and Future Thrust
Soilless farming is expanding across the globe to sustain the
growing population, and like approaches provide numerous
opportunities for producers and clients to produce quality
vegetables boosted with bioactive components by replacing
traditional farming. It is possible to cultivate various
vegetables in places with less space and reduced water
availability, so hydroponics can make a significant
contribution in such areas. Besides, it can ignite and uplift the
economic growth of a country by promoting innovative
entrepreneurship. Furthermore, since it is a controlled system,
it provides a year-round production. Therefore, low-cost
soilless and other high-tech innovations must be developed in
order to improve industrial soilless farming with lower
investment and operational costs. In the future, studies on the
subject may delve at specific methodologies and
implementation of various sorts of soilless farms. Soilless
cultivation methods include Hydroponic, Aeroponic and
Aquaponic systems. For instance, rigorous study is needed to
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precisely quantify the benefits and drawbacks of various types
of soilless farming and should further be checked to augment
the adoption of these techniques in the long run. Soilless
methods are also being considered for future space
programmes which will pave avenue for space research and
eventual habitation on Moon and Mars. In India, the adoption
is increasing, however it is still in infancy and government
should take initiation to encourage people for investing and
adoption of these techniques by raising awareness, conducting
educational seminars on the topic throughout country and
must integrate in cities to generate year round supply of food
for an increasing population.
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