Each hydroponic system, from basic homemade systems comprised of recycled plastic containers to sophisticated aeroponic systems used by NASA, relies on the nutrient solution to deliver the necessary nutrition to the plants. The nutrient solution, regardless of how it is delivered to the plant’s roots, is how the plants within a hydroponic system will receive most, if not all, of the essential elements needed to survive and thrive. An increased understanding of how plants use these elements and how to best combine the particular elements into stable fertilizers has expanded the availability of quality pre-packaged hydroponic nutrients for both the hobbyist and commercial greenhouse growers. The increase in user-friendly hydroponic nutrients is good news for beginner hydroponic gardeners or horticulturists looking to experiment with hydroponic gardening. Providing proper nutrition is a crucial component for optimizing the growth of every hydroponic garden.
The mineral essential elements needed for plant functions are broken down into two subcategories: macronutrients and micronutrients. Essential elements categorized as macronutrients are elements that are used in higher concentrations. In other words, the elements categorized as macronutrients are used by the plant at a higher rate than micronutrients. Even though micronutrients are used in lower concentrations, it doesn’t mean they are any less imperative. Both macro and micronutrients are required for optimal plant growth. The six essential elements classified as macronutrients are: nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). The eight essential elements classified as micronutrients are: iron (Fe), manganese (Mn), chlorine (Cl), boron (B), zinc (Zn), copper (Cu), molybdenum (Mo), and nickel (Ni). Together these 14 mineral elements make up the essential elements that will be found in a complete hydroponic fertilizer regiment. Aside from the essential mineral elements, scientists have discovered a few other elements that have shown potential beneficial characteristics. Sodium (Na), cobalt (Co), and selenium (Se) have all demonstrated benefits for plants (usually in very small quantities or in particular situations) but silicon (Si) is the beneficial element most commonly used by hydroponic gardeners.
The ratios of the micronutrients, macronutrients and beneficial elements in a hydroponic solution will vary depending on a multitude of factors. The type of crop, stage of growth and various environmental factors will all come into play when fine-tuning a hydroponic solution. More advanced hydroponic horticulturists use individual sources of each of the essential elements so that they are able to provide the ideal ratio for the given application. Most hobbyists, however, rely on hydroponic nutrient manufacturers to provide formulas with the proper ratios of macronutrients, micronutrients and/or beneficial elements.
Upon entering a hydroponic retailer, a consumer will quickly notice the seemingly countless options available. There are many choices when it comes to choosing a brand of hydroponic nutrients (fertilizers) and this can be overwhelming for a novice hydroponic enthusiast. Choosing a hydroponic fertilizer is kind of like buying a car. There are many options but, at the end of the day, they all get you from point A to point B. The base nutrients of a hydroponic nutrient solution do just that, get your plants from the beginning to the end. The base nutrients will contain all the mineral essential elements and will provide all that is necessary for plant growth. The essential elements found in hydroponic nutrients can be derived from a variety of sources. The varying sources will affect the formula’s stability. This leads to different types of formulas for the horticulturist to choose from. Typically speaking, there are three types of formulas produced by manufacturers of hydroponic nutrients. One-part formulas (stand-alone grow and bloom), two-part formulas (grow A and B and bloom A and B), and three-part formulas (micro, grow and bloom). A hydroponic grower will usually first choose from a one-part, two-part or three-part formula and then choose which brand of fertilizer he or she wishes to use.
A one-part formula consists of one individual grow formula and, if it is for growing a plant that produces fruit or flowers, one individual bloom formula. One-part formulas are great for beginner hydroponic growers as they only require the dosing and mixing of one product. The stage of growth of the plant(s) will determine if the gardener uses the grow or the bloom formulation. The type of crop and stage of growth will determine the dilution rate for the particular product. One-part formulas will contain all of the essential elements needed to sustain plant health. However, one-part formulas will usually contain less than optimal levels of some of the essential elements in order to make the overall formula stable. For example, many one-part formulas contain only small amounts of calcium and rely on calcium contained within the grower’s water to make up the difference. Horticulturists using one-part formulas may, in some cases, need to supplement additional sources of certain essential elements.
A two-part formula consists of two parts for both the grow and the bloom stages of plant growth. In other words, during the vegetative stage of growth, both a grow A and a grow B formula will be required. If the horticulturist is growing a particular plant variety with a fruiting or flowering stage of growth, he or she will be required to use both a bloom A and a bloom B during that period. Two-part formulas offer an advantage as they are able to separate some of the elements that would otherwise create an unstable formula when mixed in the concentrated forms. More specifically, two-part formulas are able to separate particular compounds containing concentrated calcium and phosphorus which could react poorly when mixed. A two-part formula allows the horticulturist to dilute the concentrated calcium before adding the phosphorus. This is why the part A of a two-part formula will usually contain the calcium. Generally speaking, two-part formulas can contain a higher concentration of calcium and a more ideal ratio of all the essential elements than a one-part formula.
A three-part formula consists of separate micro, grow and bloom formulas. Unlike the one-part and two-part formulas where the “grow” is used exclusively in the vegetative stage and the “bloom” is used exclusively in the fruiting or flowering stage, three-part formulas use all three parts throughout the entire life cycle of the plants. The ratio of the three parts (micro, grow, and bloom) will change depending on the particular dietary needs of the plant and the stage of growth. For example, a pepper plant in its vegetative stage will receive different ratios of each of the three parts than a pepper plant when it is producing peppers. As the names suggest, the “micro” contains most of the micronutrients (and usually the calcium), the “grow” contains nutrients more specific to growth and the “bloom” contains nutrients more specific to blooming. Although growers will use all three parts throughout the plant’s life cycle, they will typically use a higher ratio of “grow” during the vegetative stage and a higher ratio of “bloom” during the fruiting or flowering stage. A three-part formula offers heightened control to the horticulturist and gives the ability to more quickly correct deficiencies.
After a hydroponic gardener has established an effective base fertilizer program, he or she can begin to experiment with the various nutrient additives available on the market. Micronutrient supplements, carbohydrate formulas, enzyme formulas, plant vitamins, plant hormones and beneficial microorganisms are just some of the options a hydroponic gardener can experiment with. Each garden is different and the best way to determine if a nutrient additive is truly beneficial is by way of experimentation.
There are a number of other factors to consider when dealing with nutrition in a hydroponic system. One of the most important factors for any hydroponic grower to consider is the water source. A gardener’s water source should be tested to determine its mineral content, pH, and, if it is municipal water, what chemicals are being used in the treatment process. All of these factors could affect the nutrition of a hydroponic system. Many hydroponic growers opt to treat the water with a reverse osmosis (RO) system. The biggest advantage of using a reverse osmosis system is that a grower can acquire water with consistency. This is very important because if the water is inconsistent, finding the ideal ratio of nutrients for the plants can be very difficult. RO water gives a hydroponic gardener a clean slate to start with which goes a long way in building an optimal ratio of nutrition for the crop.
Nutrient solution maintenance is another huge factor to consider when discussing hydroponic nutrition. The potential hydrogen (pH) of a nutrient solution will determine the availability of all the essential elements. In order to maximize nutrient uptake, a hydroponic nutrient solution should maintain a pH between 5.0-6.0 (the optimal range usually falls between 5.5 and 5.8). Maintaining the proper temperature of a nutrient solution is also imperative to hydroponic nutrition. If the temperature is too cold, the plant’s metabolism slows down and eventually shuts down. If the temperature of the solution is too hot, the dissolved oxygen levels become too low and pathogens may enter the hydroponic system. A good general temperature for a hydroponic solution is 68 degrees F, although it varies slightly depending on which type of hydroponic system is being used.
Hobbyists may choose to experiment with different formulas in their given systems but the ultimate goal is always the same: to provide the plants with the essential elements needed to flourish while maintaining the appropriate atmospheric and nutrient solution parameters. As technology progresses and our knowledge of plant physiology increases, the hydroponic nutrients available to horticulturists will continue to improve. These improvements are very encouraging to the future of hydroponics. With “high-tech” fertilizers on the market, some complete with pH buffering capabilities, there is no doubt that the advancements in hydroponic nutrients will make it easier for hobbyists and beginner horticulturists to provide their hydroponic gardens with the essential elements needed to optimize nutrition. That is why today, more than ever; it is a great time for any horticulturist to begin experimenting with hydroponics.
Eric Hopper resides in Michigan’s beautiful Upper Peninsula where he enjoys gardening and pursuing sustainability. He is a Garden & Greenhouse contributing editor and may be contacted at Ehop@GardenAndGreenhouse.net.