The use of high intensity discharge lights are helping to change the way people do hydroponics. No longer to limited to the poor substitutes of yesteryear, the HID lamps are creating better crops than ever, but there is debate when deciding on sodium or metal halide HIDs. For some, it’s a matter of taste and preference, but true hydroponic gardeners cannot choose without looking at the pros and cons of each.
A metal halide lamp emits light by creating an electric arc under high pressure inside a bulb containing mercury and metal halides i.e. metals with bromine or iodine. It has a balanced spectrum that has been shown to enhance the growth cycle in fruits and vegetables. The crops turn out leafier and are perfect for plants like lettuce and cabbage. Halide lights tend to emit about 65-115 lumens per watt, which is less efficient than sodium.
Perhaps the biggest downfall of halide lights is they don’t last as long as the sodium variety. HID lamps are expensive and no one wants to replace the bulbs until they absolutely have to replace them. Large number of halide lamps will end up costing gardeners more in replacement costs over the years.
Everyone has seen sodium lights on lampposts for years, but high pressure sodium lights been used in hydroponics for years also. The emission of a sodium light tends to be more in the yellow and red side of the spectrum. This has shown to be helpful in the flowering phase of development and has become the preferred choice for many gardeners. More flowers on the plant means more fruit come harvest. You can’t argue with results.
Sodium lights tend to put out about 97-150 lumen per watt and last longer than their halide counterpart. It’s this efficiency that has become the cornerstone of why gardeners tend to use sodium over metal halide lights.
Why Not Use Both
The reality is that plants can grow well over their entire lifetime using either of the lamps, but they will flourish in different stages. There has been a new development involving removable ballasts that allows growers to use both lamps at different times. The clear benefit is a plant that flourishes throughout its entire lifespan. The problem is these systems are expensive and since the lamps produce different lumen, this isn’t a one size fits all opportunity.
Some hydroponic gardeners even use both at the same time. Metal halide’s broader spectrum allows it to help in areas where natural sunlight is rare such as in winter climates. Here, the halides in conjunction with sodium supplement the natural light.
The metal halide-sodium debate will likely continue as technology is developed to create specialized lights for specific plants and better efficiency. Weighing the pros and cons of both for your specific situation is the only way to make an informed decision. Both options are viable and used in greenhouses and other hydroponic gardens throughout the world, but in the end it’s what’s best for you.