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HID means “high intensity discharge”. This refers to a high output and efficient type of lighting such as halide and high-pressure sodium. The HPS is more efficient than halide, and has more in the photosynthetically active orange/red spectrum.
However, with certain genetics and environment, the use of HPS as the sole source of illumination may lead to excessive stem elongation. This is undesirable because a higher proportion of stem is produced, and the cubic area filled by the plants is increased leading to decreased light intensity. These factors reduce useful yield. Typically, stem elongation has been reduced by using halides in combination with HPS (usually in a one-to-one ratio). Now, it has been discovered that this undesirable stem growth may be avoided by maintaining lower temperatures (about 70 degrees), higher levels of light intensity, and using Power Bloom or B-9 hormone.
For side lighting, the smaller wattage color improved or Ultra-HPS lights are preferred because of the more complete spectrum. The UHPS has slightly more in the blue, and much more in the orange/red. Blue is desirable for root development and the prevention of stem elongation, and orange/red is desirable for growth and flowering. “Lumens” is a crude and inaccurate way of measuring light intensity for plant growth, because lumens represent a bell-shaped curve centered at green. I recommend using blue-spectrum fluorescents for rooting cuttings and the first few days of growth; then HPS and UHPS for flowering.
The halide ballast consists of a transformer and capacitor; they regulate the voltage and current. The HPS ballast has a different value for its transformer and capacitor, and has an ignitor circuit also. The ignitor creates a short-duration pulse of very high voltage to start the HPS (or UHPS) bulb. This necessitates a 5 KV (5,000 volt) pulse-rated socket for the 1,000-watt HPS, 4 KV for smaller wattages.
So, the halide and HPS ballasts and sockets have different requirements. This means an HPS bulb may not safely be used with a halide socket—because of the danger of explosive failure (this is especially bad since the HPS gases are heated to 4,000 degrees). However, a halide bulb may safely use an HPS socket. If a halide bulb is powered from an HPS ballast, bulb and ballast life will be shortened, and useful light per watt will be decreased. With the Advance brand ballast, for example: halide bulb with halide ballast equalsl,100 watts; HPS bulb with HPS bilast equals 1,150 watts; halide bulb with HPS ballast equalsl,330 watts (21 percent more power consumption). However, there is a 940 HPS bulb which is designed to operate safely and efficiently with a halide socket and ballast Some people learn faster than others. Senior electricians often are not qualified in the HID specialty. The science of lighting for plant growth is not static dogma to be passed down from generation to generation. It is a rapidly growing field of applied knowledge, where intelligent innovation can yield big bucks and carelessness can be very dangerous.
Let us now review the major brands of ballasts. Jefferson has increased in price and decreased in quality. Universal has increased in quality, particularly the halide. The noise level on G.E. ballasts has increased significantly; the price is way out of line.
Prototypes of two brands of 1,000-watt horticultural halide bulbs have been produced; they are now being tested at the agricultural experiment station. Crop yields are expected to improve by about 25 percent. The 1,000-watt UHPS bulb is under consideration, but technical problems remain.
If you are going to use organic fertilizers in your drip system, I recommend the Gardena brand. The water tubes and openings are larger. The Gardena system also self-regulates water pressure by a unique ball-valve action.
In a rockwool medium, I generally recommend drip irrigation with chemical hydroponic fertilizers. It is important to separate the calcium and magnesium until time of application, to minimize chemical combination and insolubility. I wouldn’t use organic fertilizers in the rockwool medium because the ammonia tends to bum, and organic fertilizer additives in general tend to be incomplete because of low potassium levels.
For flavor enhancement, organics can be successfully applied with an electric fogger. However, to minimize the danger of bud mold, make sure the humidity is low (around 40) and air circulation is adequate. I recommend air conditioning, which has the additional advantage of controlling temperature and minimizing smelly air leaks.
If you are willing to sacrifice a little yield, organics can also be applied to the medium the last few days to flush out the chemicals and enhance flavor. If pineapple juice is used for this purpose, acidity will be increased but that’s OK as long as the pH doesn’t get as low as three.
pH is not so much a goal, as a consequence of the proper ratio of primary to secondary nutrients. If the proper ratio is achieved, pH can be from three to 6.5; although with neutral tap water and a complete fertilizer the ideal pH is 5.5 to six. The question is not so much what the pH is, but why is it at a certain level. For example, if your tap water is acidic because of the presence of sulfuric acid, you may need a custom blend fertilizer. If the tap water is acidic because of the presence of pine acids, this is not usually a problem. If your tap water is too alkaline, you may need a custom blend fertilizer. If adding fertilizer to neutral tap water results in a fertilizer solution which is too acidic because of an absence of calcium and magnesium, switch to a complete hydroponic fertilizer.
There is now a better brand of container. The Imperial has many chambers in pyramid-shaped patterns to age root-circling. University tests shown increased yields compared to classic-type design. The classic designed specifically to di root-circling, it is only slightly more than normal pots. The classic share designed to stiffen the pot is cheaper.