Since all bulb vegetables are low-growing herbaceous plants, it is easy to grow them by using hydroponics growing technology. In fact, chives and leek are considered as some of the best crops suitable for greenhouse hydroponics. Onions, garlic and shallots are suitable for outdoor hydroponics.
Hydroponics is a practice of growing plants in a nutrient-rich solution, without soil. Today the term ‘hydroponics’ has become synonymous with ‘soil-less production of crop plants’ though the term itself means that it is water (‘hydro’ means ‘water’) that is at work (‘ponics’ means ‘labor’ or ‘work’). The term ‘hydroponics’ may seem to represent a sophisticated process but in reality, hydroponics is a simple process of crop production. The only difference of a hydroponics crop production from that of a traditional method is that hydroponics makes use of a nutrient solution as plant growing medium instead of soil.
Generally speaking, hydroponics under controlled environmental conditions (i.e. greenhouse hydroponics) is more successful than that of outdoor hydroponics.
Hydroponics is based on the principle that plant growth in a traditional soil-based production system is not dependent on the soil rather it is dependent on the nutrients and moisture present in the soil. So, if the plant nutrients and moisture required for the plant growth are provided through any other medium other than the soil, plants can still have a natural growth. Therefore in a hydroponics system, ideal nutrient and moisture requirements of the plants are fulfilled through a water culture or solution culture under ideal environmental conditions. In other words, hydroponics is soil-less crop production system under controlled environmental conditions.
There are mainly two types of hydroponic grow systems: Aggregate systems and Deep Water Culture (DWC) systems. In aggregate systems, growing media such as perlite and rock wool are used as plant supporting systems. DWC systems use only water culture or nutrient solution to grow the plants. These systems do not use any aggregate growing media as plant root support system. The plant roots are totally suspended in the nutrient solution. A tray made of plastic or Styrofoam boards or similar materials that float on the surface of the solution is used to support the plant above the solution. Holes are provided on the tray so that the roots are inserted into the solution while the shoots stand on the tray growing upwards.
In DWC systems, the nutrient solution needs to be aerated or bubbled continuously by using an air pump and air stones. Nutrient solution should be changed regularly and kept at constant level in the reservoir tank. Best examples of popular DWC systems are Nutrient Film Technology (NFT) and BubblePonics. NFT is one of the most popular water culture hydroponics systems used for growing chives. BubblePonics or bubble hydroponics is water culture hydroponics where constant oxygenation or aeration of the plant root zones is required for the healthy growth of the plants.
A standard DWC hydroponics grow system is divided into TWO areas: a propagation area (propagation room) and a grow area (grow room). Propagation area is where propagation takes place while grow area is exclusively dedicated for vegetative growing purposes.
A standard hydroponics system includes grow trays, reservoir tanks, plant pots, plant nutrient kits , pH test kit, digital TDS meter, water pumps, air pumps and air stones, air diffusers, growing media kits, starter materials (seeds, clones), and a plant starter tray. The system should have air filters, duct mufflers or silencers, and a light proof system .Safety of operations is ensured in a hi-tech hydroponics system by providing provisions for fire protection, and insulation.
Propagation: It is advised to start planting materials in the hydroponics system itself. This helps avoid transplant stress for the plants. Propagation within the hydroponics system will also help the growers obtain disease-free and pest-free starting materials. A separate propagation room may be used for propagation purposes.
Propagation room should be specifically designed for facilitating propagation process by providing optimum temperature, light and humidity conditions. A standard propagation system available with the hi-tech hydroponics system includes a starter tray, a humidity dome, a seedling heat mat, a heat mat thermostat and a growing media kit. A starter tray is used for seed germination. Seedlings are grown here until they attain transplanting age. Starter trays are made up of durable plastic and come with a reservoir tank in which nutrient solution is prepared to be supplied to the seedlings. A humidity dome is used for providing optimum humidity conditions for accelerating germination process. Heating the root zone of germinating seeds is important for achieving their optimum growth. Seedling heat mat is used for this purpose in a hydroponics system. A heat mat thermostat may be used to regulate the temperature of the heat mats.
Seeds are sown directly on the starter/seed tray that is filled with a growing medium. After sowing, tray is covered with a lid. The growing medium is constantly kept moist by pumping the nutrient solution kept in a reservoir tank. Rockwool is the most popular growing media used in the hydroponics. Rockwool cubes with a hole in the center are popularly used for seed propagation. These cubes are soaked in water or nutrient solution before placing seeds into the hole. Cubes are kept moist until the germination process is completed and seedlings are ready for transplanting.
Seedlings, when they are ready for transplanting, are taken to the grow room. A grow room has a perfectly balanced environment with proper ventilation, humidity, temperature and light management system. A controlled environment such as a greenhouse is recommended for growing kale and celery because such a system provides shelter, and stress-free environment for the plants. Temperature of the growing environment may be monitored regularly by using a thermometer. Temperature within the growing environment should be kept at 50- 70 degrees F (10-200C). High Temperatures may induce bolting in the plants and thus destroy them. A hygrometer may be used to measure the humidity inside the growing environment. A well-designed hydroponics system has cross air flow system to ensure adequate aeration around the plants and their root zones.
Preparation of Nutrient Solution: For healthy plant growth, a plant needs both macronutrients and micronutrients (trace elements). Major macronutrients include Nitrogen (N), Phosphorous (P), Potassium (K), Calcium (Ca), Magnesium (Mg), and Sulphur(S). Trace elements are Iron (Fe), Manganese (Mn), Boron (Bo), Zinc (Zn), Copper (Cu), and Molybdenum (Mb). Nutrient formulas containing all these nutrients in correct proportions are available in the market as hydroponic nutrient mixes. A grower may purchase them to prepare the nutrient solution for the hydroponics.
Regarding, preparation of the nutrient solution, care should be taken that only good quality water is used. Hard water should be avoided by all means. Periodical flushing of the nutrient solution is necessary to prevent salt build up in the solution.
While preparing an ideal nutrient solution, pH, electrical conductivity (EC), temperature and total dissolved solids (TDS) of the solution should be measured as each of these parameters has an impact on the degree of nutrient absorption by the plant roots.
Optimum pH range for the nutrient solution should be maintained always. Large variations in the nutrient pH may lead to poor absorption of nutrients by the plants.
pH of the nutrient solution can have a great impact on the plant growth. Since every plant has a preferred pH range at which plant nutrients become available to its growth, solutions having too low or too high pH should be avoided in a hydroponics system. pH of nutrient solution should be checked regularly by using any of the pH devices available in the market. Cheap pH devices such as a pH control kit and pH pen may serve this purpose for those who are looking for cost effectiveness. A pH meter may be a costly device as compared to a pH control kit but provides instant reading.
Electrical Conductivity (EC) of nutrient solution should also be kept at desirable range. EC refers to ‘electrical conductivity’ or flow of electric current through the nutrient solution. EC and concentration of the nutrient solution is proportionately correlated. i.e. when the concentration of nutrients is higher in the solution, EC will be higher and vice versa. EC meter is used to measure the electrical conductivity of the nutrient solution. EC meter records the reading in either micromhs per centimeter (uMho/cm) or microsiemens per centimeter (uS/cm).
The temperature of the nutrient solution affects the reading of the EC meter. Hence it is recommended that EC should be measured at 250 C always. If the temperature of the nutrient solution is above 250 C, the EC reading will be higher, even though concentration of the solution remains same. If the temperature of the nutrient solution is below 250 C, EC reading will be on the lower side.
An ideal hydroponic growing condition for the bulb vegetables such as for Chives (and for other members of onion family) is as follows: EC: 1.8-2.2; pH: 6.1-6.8; and temperature: 65-80º F; light: 12 hrs minimum
Another important consideration is TDS. Total Dissolved Solids (TDS) of the nutrient solution should also be kept at desirable range. TDS refers to the total dissolved solids present in the nutrient solution. A TDS meter is used to measure TDS level of the nutrient solution. The meter reading is shown in parts per million (ppm).
In hydroponics, the roots of the growing plants should be aerated at regular intervals because plant roots need oxygen in order to survive. This oxygenation of roots may be carried out by using highly efficient air pumps and air stones.
Remember, good aeration of the hydroponic solution is essential to obtain the best results.
If nutrient solution is poorly aerated, it adversely affects the root development. A healthy root system is white coloured and highly branched. In poorly aerated solution, roots develop browning and turn to dark colour.
Regular monitoring of the nutrient solution provides the grower an idea about the status of the nutrient solution.
Regular testing of the nutrient solution for pH, EC, and TDS helps growers ensure that plants are being fed with right nutrients at right concentration. It also helps monitor the salt levels of the nutrient solution at every phase of crop production. Thus growers can take appropriate corrective measures if the salt levels rise unexpectedly resulting in a ‘salt build-up’ in the growing system.
Two important corrective measures recommended for eliminating problems associated with salt build-up is regular flushing of the growing medium with a fresh nutrient solution or replacing the nutrient solution with a fresh one.
Remember, temperature of the nutrient solution should always be lower than the air temperature.
Tips for Successful Nutrient Application
- Whenever a nutrient solution is prepared, use a measuring cup to take correct quantities of nutrients
- Make sure that nutrients are taken in correct proportions
- If nutrients are in powder form, use warm water to dissolve them and mix well by stirring vigorously to get a homogenous solution
- Use a PPM (parts per million) measuring device (e.g.: nutrient monitor) to measure the concentration level of the nutrient solution
There should be an air filtration system in the growing system. Carbon filters effectively eliminates undesirable odours from the grow system. Adequate lighting should also be provided for the growing plants@10-18 hours of light/day. Fluorescent grow lights or LED lights may be used for providing artificial light.
LED lights are highly energy efficient and economical. LEDs are low temperature way to increase the amount of light that plants receive. Light distribution and coverage within the system can be adjusted by installing panels and reflectors.
Placement of the lights should be directly related to the intensity of the light required by the plant. If more light intensity is required, place the light close to the plants but not too close to burn the leaves. Adjustable lighting system may be used to adjust the light according to the plant requirement.
In hydroponics, care should be taken not to expose the roots of the growing plants to the light. Root exposure to light may induce growth of algae and thus contaminate the growing medium.
CO2 forms an integral part of a plant growth system and therefore it is important that CO2 should be applied in a hydroponics system for healthy plant growth. Generally CO2 is administered to the plants through a tank application process.
Significance of Light Energy and CO2 in Hydroponics: Plants need light energy for various purposes, major being photosynthesis and transpiration. During photosynthesis, plants produce carbohydrates (foods) using light energy, carbon dioxide and water. In an enclosed hydroponics system, artificial lighting system and CO2 application system may be used to provide the light and CO2 needed by the plants.
In indoor hydroponics in greenhouses, pests and disease can also be effectively controlled by protecting the greenhouses from the entry of insects and pests. Wire meshing may be used at all entry points to prevent pest infestation. If proper hygiene is practiced within the greenhouses, disease incidences can be minimised to nil.
In well-managed hydroponic grow systems, a grower can produce a good quality crop within a span of one or two months. Both quality and quantity of the crop can be optimised in a well-managed hydroponic grow system.
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