Q: "I have a few questions on hydroponics. I am currently working with a team and we are making a hydroponic garden out of an old shipping container. So far we plan to use PVC pipes as the main system and purple lighting (almost like purple party string lights) as our source of light around the container. One of the things we are looking into is, what are common problems we will face and how to find the optimal, temp, humidity, pH, etc. in the container so as to avoid any unwanted pests (algae, gnats, mildew, and other plant diseases). If you know any good tips or ways to go about experimenting please let me know."
A: Shipping containers have been turned into highly successful hydroponic systems in many different climates and they can be a good choice for a compact and productive indoor garden. The main considerations with this type of set up are air flow, humidity control, plant density (i.e., not overcrowding the system), the correct type of lighting and temperatures.
Since the volume of air inside the container is highly limited, factors such as heat and humidity can build up very rapidly when plants are large and grown at a high density. Humidity build up inside a shipping container often leads to condensation on the roof which falls onto the plants, thus greatly increasing the risk of a disease outbreak.
For this reason, the rate of air flow into and out of the container must be sufficient to remove moisture from the air and control temperatures. The recommended rate would be at least one complete air exchange between the inside of the container and the outside per minute (60 air exchanges per hour) and in some climates, dehumidification may also be required. This will be more important as the plants grow as a large surface area of foliage releases much more water vapor into the air.
Secondly, temperature control is also vital, in warm, tropical climates, shipping containers with chilling (i.e. climate control) are used to grow cool season crops such as lettuce when conditions outdoors are too hot for good growth. So the requirement for heating and/or cooling will depend on the local climate where the container is sited – insulated shipping containers are a good choice where a high degree of heating and/or cooling is required to achieve the optimum levels for plant growth.
Lighting for crop growth is also very specific, horticultural LED lamps are recommended for very confined, small spaces as they don’t put out the high heat of HID lamps, they can also be placed just above the plants without the risk of leaf burn. Light for plant growth is very specific and a little different from lighting used for other purposes, so it would be a good idea to consult a reputable supplier of hydroponic equipment to make sure the correct type, layout and intensity of lamps are chosen.
Algae growth can be prevented by making sure the nutrient solution flowing inside the PVC pipes and in the nutrient tank is never exposed to light (light proof covers assist with this).
Fungus gnats can be prevented in a similar way by covering any exposed, damp growing medium and nutrient solution, and preventing algae growth (gnats are attracted to moisture and organic matter).
Other insect pests are more difficult to prevent, however screening over air intakes, vents and a small double door entry into the shipping container may help as well as carefully inspecting any plant material coming into the container for pest infestations.
Daily checking and adjustment of the hydroponic system EC and pH should be sufficient to manage the nutrient in a recirculating PVC system, however it would be advisable to make sure you have a high quality, clean water source or use reverse osmosis (RO) water.
Good luck with your container garden!
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