Food security and safety has becoming a challenge due to changing climate (13-45% yield losses by 2040), sprawling population (global 9.6 billion humans by 2050 while ~ 1 billion people malnourished), losses of arable land and dietary changes.
By Dr. Nazar Faried*, Dr. Ishtiaq A. Rajwana, Dr. Gulzar Akhtar, Dr. Syed Bilal Hussain, Ali Asad Bahar
1. Introduction
Besides, the growing food crops are facing several soil/ ground and air-borne biotic and abiotic challenges along-with higher future land requirement, inefficient and higher water, nutrient and pesticide utilization. Besides, increasing population of Pakistan demands 150% increase in cropping intensity annually. Therefore, crop cultivation systems need transformation for food security and environment sustainability through efficient resource (water, nutrient, environment, and others) utilization. Hence, increase in crop productivity and quality. Currently Urban agriculture has been diversifying. For example, greenhouse vertical cultivation, aquaponic, edible landscaping and hydroponics/ soilless farming.
Greenhouse hydroponics / soilless farming involves growing crop plants without soil in an aqueous solvent or inert media (perlite, vermiculite, coconut fiber, peat moss, etc) for an extended period by using mineral nutrient solution. Plants are provided defined quantity of water, minerals, and oxygen as per crop growth stage. William Frederick Gericke during 1930s named it hydroponics which means water working. Hydroponic system ensures earlier, higher, and vertical crop production at any place by utilizing less resources under controlled growing environment (light, temperature, humidity, and airflow) throughout the year. Globally, it is growing at ~19% annually with maximum production in France, Netherland, Spain, and USA. NASA declares it future farming especially for astronauts in space. This technology can further be explored to produce high value crops like vegetables in areas with either limited or doesn’t exist or degraded soils (e.g. salinity) or water stressed areas to ensure food security.
2. Hydroponic/ Soilless Systems
Broadly, hydroponic systems divide into closed/ recovery or open/ non-recovery systems. In closed system nutrient solution is continuously recycled. The drained nutrient solution is collected, monitored, adjusted, and recirculated. It does not use growing media. On the other hand, open system uses growing media (e.g. coconut coir). It may either be closed (nutrient solution is recycled) or open system (nutrient solution is provided during each fertigation cycle and discarded). Different hydroponic/ soilless systems have been developed through R&D for different crops depending upon growth behavior, and season. For examples, Drip systems (it’s an extensively used system in which nutrient solution provided to plant roots by drip line. Drain/ run-off is reused in recovery/ closed system while not in non-recovery/ open system. Figure 1), Nutrient Film Technique (NFT) (It is closed system which involves continuous flow of nutrient solution from a reservoir to plant roots in grow trays, drain to reservoir and again pumped to grow trays. Figure 2). Wick system (Plants uptake water and nutrient with wicks from a reservoir containing nutrient solution through capillary action. Figure 3), Deep Water culture (Plants are held in light weight Styrofoam platform that floats on nutrient solution with roots directly immerse in the solution and oxygen supplies by air pump. Figure 4), Ebb & Flow (Flood and Drain) (It involves flooding nutrient solution to the plant roots held in grow tray filled with growing media by submersible pump and draining back to reservoir numerous times a day through timer. Optimum oxygen is ensured by air pump. Figure 5), Aeroponic (This system is same as NFT except the nutrient solution is applied like mist on the hanging roots at regular interval to avoid root drying. Figure 6) and Aquaponics (Rearing fish, plants, and beneficial bacteria together in a single water source. Nitrifying bacteria converts fish waste ammonia into nitrite and nitrates which are used as a source of plant nutrition while plant roots uptake nutrients and filter the water for fish consumption. Oxygen ensures through air pump to avoid anaerobic conditions. Figure 7) (courtesy: https://www.simplyhydro.com/system/)
3. Advantages of Hydroponic System:
Following are the few advantages of Hydroponic/ Soilless cultivation
Efficient Water Consumption
Climate change is prevailing globally and disturbing the natural ecosystem. Pakistan listed as the 5th most vulnerable country exposed to climate change and the 3rd most water scarce country. Water will become a critical issue in future when food production requirement is predicted to increase by 70%. Besides, sewage and industrial affluent’s enriched irrigation are the major source of soil pollution in urban and peri-urban growing food system particularly leafy and root vegetables. In this scenario, hydroponic cultivation is considered as a viable solution for water saving (70-90%) relative to open field cultivation especially under closed loop fertigation system included run-off collection, filtration and recirculation system for large-scale food production to ensure higher yield and improved quality under controlled environment greenhouse system.
Efficient Nutrient Utilization
Hydroponic cultivation success depends on the provision of three fundamental things (quality water, oxygen, and nutrients) that leads to optimize plant growth and development, thereby early, higher and quality production. The plants require seventeen essential nutrients in which carbon, hydrogen and oxygen (non-mineral macronutrients) are obtained from air, water, or both while nitrogen, phosphorus, potassium (mineral primary macronutrients), calcium, magnesium, sulphur (mineral secondary macronutrients), boron, copper, iron, zinc, manganese, molybdenum, nickel and chlorine (mineral micronutrients) are provided in the form of fertilizers. Productivity and quality of crops depend on plant’s ability to acquire nutrients from the growing medium. In hydroponic growing systems, nutrients are dissolved in water and directly uptake by plants to use for food production compared to soil in which nutrients 1st adhere to soil particle followed by soil solution and uptake by plants. Therefore, growers have complete control on concentration { electric conductivity (EC) } and pH of the nutrient solution to ensure fast growth during vegetative and reproductive phases. The nutrient solution containing macro and micro-nutrients are provided in specific concentration (1.3-2.5 EC), pH (5.6-5.8) and temperature (22-24°C) to ensure maximum root uptake, thereby optimum growth, early and maximum crop production. Moreover, the drain/ run-off nutrient solution is collected, tested, adjusted, and reused for maximum nutrient efficiency. In this regard, hydroponic cultivation system utilizes less fertilizers (~ 60%) compare to traditional methods.
Optimal Growth Environment
Greenhouse (transparent material structure such as glass, polycarbonate, polythene etc) environment (temperature, relative humidity, and light) ensures optimize growth eco-system, protects from extreme weather along-with disease and pests through ventilation, transparent cover and shade to growing plants, thereby higher crop growth and productivity (3-10 times) including off-season for extended period (9-11 months) than that of open field grown crops (4-6 months). Besides, vertical space is utilized with increase planting density compared to open field. The high value crops like tomato, cucumber and pepper grow vertically. They require specific growth environment including temperature (25-28 °C), relative humidity (60-70%) , CO2 enrichment (700 and 900 μl l−1) and optimal light (covering 40% shade at noon during summer) that’s ensure through retractable environment-controlled greenhouse. Controlled environment accompanied with soilless cultivation has been helping growers for efficient resource utilization (water, nutrient, light, pesticides) and superior produce. Hence, greenhouse hydroponic growers have complete control over the temperature, relative humidity, light intensification, and composition of the air year round regardless of season and land type (waterlogged, saline, and desert) to ensure food security and safety with maximum farmer’s profit.. Currently, this technology has been adopted commercially by more than 50 countries including USA, Holland, Spain, Italy, Turkey, China, Japan etc for floriculture (gerbera, lily, freesia, iris, etc) and vegetable crops (tomato, cucumber, capsicum, melons, strawberries, beans, etc). For instance, 132% increase in greenhouse soilless production of herbs and vegetables was recorded in USA alone during 2012-2017.
Weed Free Growing Environment with Least Insect-Pest and Disease Spread
Weed (an undesirable plant in human controlled crop field) is associated with soil, more efficient in using crop production resources (light, space, water, nutrients) and acts as a source of insect-pest and disease spread and may cause crop productivity loss upto 50%. Insect-pest and disease pathogen particularly soil-born develops and retain in rhizosphere year after year and negatively affects the crop production. Being tender crops, vegetables are more susceptible to insect-pest and disease attack. Farmer managed by continuously spraying the vegetable crops with chemicals which not only pollute the soil and aerial eco-system but also harvest produce and consumer health. However, hydroponics system is entirely clean and weed free. Resources (space, light, nutrient and water) are delivered to roots for optimized crop cultivation horizontally and vertically without weed management practices. Moreover, soilless greenhouse system ensures limited chances of external contaminants (insect/pest) and least insecticide/pesticide sprays, thereby producing high quality horticultural produce including tomato (plum, beefsteak & cherry), bell pepper, chilies, cucumber, strawberry, lettuce, mint, cabbage, beans, coriander, peas, etc.
Higher Crop Productivity and Quality
Greenhouse hydroponic farming of high value crops relies on manipulating plant nutrition factors (quality water, slightly acidic pH and EC) as per growth stage, delivering intensive nutrient solution and oxygen directly to roots, homogenous growth eco-system (temperature, humidity, light, air circulation) for extended period along-with vertical cultivation and higher planting density. Besides, better crop management practices (plant pruning, training, fruit thinning, etc) with least disease and insect-pest proliferation compared to open field soil cultivation lead to faster growth, earlier harvest, larger crop production (3 to 10 times) for extended period (9-11 months, longer shelf-life, persistent quality, nutritious and healthier produce (↑mineral and vitamins) with least postharvest losses, thereby higher consumer acceptance and farmer profitability.
Conclusion
Globally, soilless cultivation has been expanding for early, higher, nutritious, and quality production with consistent supply throughout the year by ensuring maximum resource use efficiency with minimum postharvest losses under environment-controlled system, thereby higher grower profitability and consumer satisfaction. However, several challenges including technical human resource, economical nutrient recipe, expensive greenhouse and environment-controlled technology and crop calendar as per market and environment particularly in developing countries like Pakistan need consideration for its sustainability. In this regard, MNS University of Agriculture, Multan (MNS-UAM) has been working on soilless farming since 2017 vis-à-vis exploring South Punjab environment for high value vegetable production (e.g. beefsteak, plum and cherry tomato, colored bell pepper), crop calendar development, varietal evaluation, economical nutrient recipe development, postharvest and nutritional quality testing as well as technical human resource development who will serve as the future managers or entrepreneurs or serve in foreign country greenhouse industry (e.g. Middle east). Moreover, MNS-UAM is working on technology outreach to different stakeholders and consultancy services in the country.
*For more information: Dr. Nazar Faried, Assistant Professor,Dept. of Horticulture, MNS University of Agri., Multan.
Source: https://www.technologytimes.pk/2021/04/22/hydroponics-a-future-technology-for-sustainable-food-security/
Hydroponics A Future Technology For Sustainable Food Security
26 April 2021
