Hydroponic culture methods do, however, have certain drawbacks, including a high setup cost, a quick pathogen spread rate, and a requirement for specialised management expertise.
Worldwide acceptance and widespread usage of hydroponic systems for a variety of uses across many continents. This review’s objective is to provide information about hydroponic systems, such as the many types and operating procedures; trends, benefits, and drawbacks; and the function of helpful bacteria and fungi in lowering plant illness and enhancing plant quality and production.
Numerous modified hydroponic systems, including the wick, drip, ebb-flow, water culture, nutrient film method, aeroponic, and windowfarm systems, have been created in order to grow more and better hydroponic crops.
Numerous studies have shown that hydroponics has several benefits over field culture methods, including the reuse of water, simplicity in managing environmental conditions, and a reduction in conventional agricultural practices (such as cultivating, weeding, watering, etc.).
Hydroponic culture methods do, however, have certain drawbacks, including a high setup cost, a quick pathogen spread rate, and a requirement for specialised management expertise. Due to the high nutrient concentrations in hydroponic systems, numerous phytopathogens may also develop quickly and destroy the entire crop by quickly spreading via the water circulation system.
We concentrated on biological controls, particularly plant growth-promoting rhizobacteria that are utilised as biofertilizers, biocontrol agents, and bioremediators, among other ways used to control diseases with physical, chemical, and biological means.
This review aims to improve knowledge of hydroponics, newly implemented systems, and method optimisation in current systems to lessen plant illnesses and improve food quality and quantity.
Growing techniques known as hydroponic systems substitute nutrient solutions for dirt substrates. The supply and demand for hydroponic systems have grown significantly in the United States as a result of the better yields and higher-quality goods that can be produced using hydroponic production techniques.
In affluent nations, a lot of hydroponic crops are grown to satisfy customer demand. Hydroponic research has grown substantially over the past few decades, particularly in the areas of increasing crop output and overcoming hydroponic system limits.
Hydroponic systems have been used to study a wide range of crops, including beans, cucumbers, lettuce, tomatoes, etc. The two nations that produce the most publications concerning hydroponic plant systems are the US and China.
Despite the fact that hydroponics is frequently employed for home gardening, instruction, and research, most systems have been employed in the production of cut flowers and commercial vegetables. According to the needs of various plants, the majority of hydroponic systems automatically adjust the quantity of water, nutrients, and illumination duration.
The type of hydroponics being used, the cost, and the characteristics of the plants all influence the medium choice. Since almost all hydroponic systems are indoors and found in greenhouses, they may be less dependent on the weather outside and have a less environmental effect than a soil culture system.
Since hydroponics systems offer so many advantages, they are frequently utilised to cultivate a broad variety of plants in many different industries, and the demand for hydroponically grown food is rising. However, there is a problem with how hydroponics treats waste water and non-renewable resources.
Additionally, through the water tubing systems, waterborne pathogens can pollute and spread. The most typical plant infections found in hydroponic systems include Colletotrichum, Fusarium, Phytophthora, Pythium, and Phizoctonia species.
Hydroponic models: types and methods of operation
Although closed hydroponic systems are more cost-effective than open systems, open hydroponic systems may generally be less sensitive to the salt of the water.
Five commonly used hydroponic systems are described here: the wick, drip, ebb-flow, water culture, nutrient film, and windowfarm model, which has been recently introduced.
The wick system:
According to Shrestha and Dunn (2013), the wick or passive system is a great model for growing indoor plants since it is self-feeding and doesn’t need a water pump.
Water or a nutrient solution is supplied in a reservoir using a wick or fibre material (often nylon) that may absorb and convey water from the reservoir to the root area via capillary action. The wick method has been used to grow flowering plants in small-scale gardens, such as private homes or office gardens, due to its simplicity of usage.
The wick method is not ideal for large or long-lived plants because they require more water than the wick can provide, even if it efficiently prevents the illnesses associated with overwatering (Harris, 1988).
The drip system:
Since many years ago, the drip irrigation system has been extensively employed in commercial systems (Reed, 1996). Each plant or pot is supplied with water or a nutrient solution by a pump in the reservoir, and the amount of water each plant receives is controlled by an electronic timer (Fig. 2b) (Rouphael and Colla, 2005).
The drip system is divided into two models: recovery and non-recovery, depending on how the recycled water or nutrient solution is treated (Saaid et al., 2013).
The recovery system collects the water or nutrient solution, empties it into the reservoir, and then cycles it once again (Schröder and Lieth, 2002). Reusing the solutions might result in pH changes and the growth of mould or algae in the reservoir or tubing system, although it’s not necessarily a good idea.
But as a result, it is more economical than the non-recovery approach. The drip system’s total output without recovery The amount of water or nutrient solution in the reservoir has to be monitored on a frequent basis to ensure that enough reaches the roots of the plants (Santamaria et al., 2003). The system is further vulnerable to power disruptions that cause plant stress or death.
The ebb and flow system:
The automatic flood and drain watering approach is used by the ebb and flow system, one of the earliest commercial hydroponic systems, to water plants on a regular basis and for brief periods of time (Buwalda et al., 1994).
The employment of several media at the root area is the system’s strongest point. The water or nutrient solution in the reservoir ascends to a growth tray using a water pump, accumulates to a specified level, and stays in the growth tray for a predetermined amount of time to provide water and nutrients to the plants.
After a certain length of time, the solution is drained back into the reservoir using a tube system. Constant inspection is required to manage the water flow in this circulation system.
Despite the fact that a wide variety of plants may be cultivated and provided with a lot of water, this method is prone to root sickness and the development of algae or mould. Because of this, a few customised ebb-flow systems have been created. Systems are used to sterilise the water by the use of a filtration step or another method (Buttner et al., 1995; Nielsen et al., 2006).
The (deep) water culture system:
The bulk of modified hydroponic systems were primarily inspired by the water culture system (Harris, 1988). The fundamental components of the water culture system are a reservoir, an air stone, a tubing system, an air pump, and a floating platform (Hoagland and Arnon, 1950).
The development of aeration techniques to preserve dissolved oxygen led to the development of the deep water culture system, which allows for the continuous floatation of roots in water throughout plant growth. In contrast to the wick approach, it actively creates food.
In a reservoir, where the root systems are continually submerged in water or nutritional solution and oxygen is supplied by an air pump and air stone, plants or pots are supported by a floating platform. Optimising growth conditions requires constant monitoring of salinity, pH, oxygen, and nutrient contents (Domingues et al., 2012).
Although huge or long-term harvests would not be possible with this strategy, all plants, notably cucumber and radish, grow well, and algae and moulds can spread swiftly in the reservoir.
Nutrient film technique system:
The nutrition film technique (NFT) approach was created in the 1960s to address the shortcomings of the ebb and flow systems. NFT systems may continually feed water and nutrients and create oxygen-rich conditions by controlling flow and water depth (Fig. 2e). (Jones, 1997).
After entering the growing tray by a water pump without a timer, a nutrient solution or water is continually circulated around the roots in the system (Domingues et al., 2012).
The solution is collected and utilised again after the volume of water is controlled by the water pump’s force and the tray’s slope. The roots are frequently submerged in water or nutritional solutions due to their constant exposure to moisture, which makes them vulnerable to fungal infection (Thinggaard and Middelboe, 1989).
Advantages of hydroponics:
Hydroponic systems have a number of benefits over soil culture methods. Even in locations where the soil is contaminated with hazardous substances or heavy metals, hydroponics is effective for growing crops (Jones, 1997).
In order to maximise crop output, indoor hydroponic systems also make it simple to adjust growth variables, including temperature, water flow velocity and volume, nutrients, relative humidity, and illumination duration (Norén et al., 2004).
Additionally, plants grown in hydroponic systems are less susceptible to the effects of climate change, enabling year-round cultivation of plants in a variety of environments (Gibeaut et al., 1997; Manzocco et al., 2011; Norström et al., 2004).
Additionally, since the systems run automatically, it is possible that they will cut labour and various other costs. It is possible to do away with common agricultural practices, including cultivating, weeding, watering, and tilling (Jovicich et al., 2003).
Issues | Hydroponic system | Soil Culture | Reference |
|---|---|---|---|
Land use and environmental impact | Less adversely affected by the environment and the soil. Indoor system; simple fertiliser control; environment control (including temperature, humidity, and lighting schedules); year-round cultivation anywhere. | Undesirable if soil contains heavy metals and plant diseases; constrained by soil nutrients; difficult to manage external surroundings; In certain places, year-round cultivation is restricted. | Gibeaut et al. (1997), Jones (1997), Norén et al. (2004), Norström et al. (2004) |
Labour | Traditional methods are mainly eliminated. | Tilling, cultivating, weeding, watering, and other procedures | Jovicich et al. (2003) |
Sanitation | Preserving hygienic conditions and allowing for simple handling of all products and the medium | It is challenging to regularly maintain sanitary conditions and to sanitise the soil and the equipment. | Knutson (2000) |
Diseases and pests | Prevent soil-borne illnesses, make it simple to control insects and animals, and use fewer pesticides. | Insects and animals that are difficult to control (losing agricultural output) and soil-borne illnesses | Zlnnen (1988), Jones (1997) |
Water | Water is used efficiently, it may be recycled or reused, there is no nutritional waste from runoff, and water reaches the root zones directly. This has the potential to regulate water-holding capacity by utilising different types of media. | Ineffective water use; inability to recycle or reuse water; environmental eutrophication brought on by runoff; difficult to regulate water-holding capacity | Güohler et al. (1989), Midmore and Deng-Lin (1999) |
Fertilisers and nutrient solutions | Even distribution to crops, cost-effective fertiliser application, simple pH and nutrient quantity management | Partial nutrient deficit in crops due to uneven distribution; frequent overuse of nutrients; significant variability; difficult pH and nutrient management | Rolot (1999), Resh (2013) |
Quantity and quality of the crop | Production is consistent and uniform, ranging from 14 to 74 kg per m2 for tomatoes to 6900 kg per m2 for cucumbers, 5200 kg per m2 for lettuce, and 5 kg per m2 for beans, all with consistent quality. | Production is unstable and unequal owing to pests and soilborne diseases; tomato yields range from 1.2 to 2.5 kg per m2; cucumber yields 1700 kg per m2; lettuce yields 2200 kg per m2; and bean yields are inconsistent in terms of quality. |
Limitations of hydroponic systems:
• High initial setup costs for supplies and ongoing maintenance costs
• Production of waste materials and high-nutrient hydroponic waste solutions
• vulnerability to power outages resulting in issues with water or nutrient delivery and withering.
There are a number of drawbacks to using hydroponic systems, including:
• Easy spread of phytopathogens through water tubing systems
• There is a need for experts to maintain the systems for optimum production.
• Background nutrient requirements for controlling nutrient levels
• Growth of unwanted algae and fungi in nutrient solutions
• Biofilm buildup in the system interferes with nutrient uptake and shortens system life.
Not all plants are suitable for hydroponic systems.
Beneficial bacteria in hydroponic systems:
Due to the high nutrient concentrations in hydroponic systems, many diseases can flourish there. By moving tainted water through the system, pathogens can be transferred to crops and may destroy the entire crop.
Even though closed hydroponic systems can lessen the emission of a lot of waste hydroponic solutions, they have a possible risk of accumulating poisonous substances and dangerous plant infections. In hydroponic systems, these chemical control approaches may also result in a decline in the population of helpful microbes.
We and others have investigated how rhizobacteria that promote plant development affect hydroponic systems. The introduction of PGPR has had favourable effects on plant quality and quantity in both soil-based and hydroponic systems.
Environmental conditions and the supply of fertilisers may have an impact on the microflora in hydroponic systems. Plant pathogens are sometimes present in the microflora, although they are often outnumbered by non-pathogenic organisms. Bacillus species. Additional studies with Bacillus spp. Despite the way in which Bacillus spp.
Conclusion :
Due to their obvious benefits over soil cultures, hydroponic systems have become more popular in both home gardening and agribusiness. Undoubtedly, new technologies will be developed to solve these issues, especially as we learn more about the processes by which beneficial bacteria support plant development and guard against phytopathogen harm.
This article is jointly authored by Abdul Rehman Javed and Hira Javed from the University of Agriculture, Faisalabad.