All plants need nutrients to live. In traditional gardening and farming, plants get their nutrients from the soil and additives such as compost, manure, and chemical fertilizers. In hydroponics, plants are not grown in soil, so nutrients must be delivered directly through a watering solution.
These nutrients are divided into two categories: macronutrients and micronutrients. Macronutrients are those that plants need in large amounts, including carbon, phosphorous, hydrogen, nitrogen, oxygen, sulfur, potassium, magnesium, and calcium. Micronutrients are needed in tiny amounts but are essential. These include zinc, nickel, boron, copper, iron, manganese, molybdenum, boron, and chlorine.
Without these essential elements, plants are unable to build molecules, undergo enzymatic reactions, and complete their life cycle. For hydroponic gardeners, this means that without proper nutrients, the plants cannot produce quality fruit or vegetables or strong plants for transferring to a soil environment.
Plant pH Needs
When developing a nutrition program for hydroponics, pH levels are also an essential element to consider. pH is a measure of the hydrogen ion concentration or acidity of the solution. Measured using a 0- to 14-point scale, 0 is the most acidic, 7 is neutral, and 14 is the most alkaline. The pH value of a nutrient solution has a huge impact on the amount of nutrition that a plant can absorb. It is essential to check pH levels regularly, preferably daily, even if you are careful about measuring and mixing your nutrient solution.
Plants have different requirements for pH value and nutrient concentration. If you are going to be growing a large variety of plants in your system, make sure to research the requirements for each so that you can group them in terms of their pH needs.
A single plant’s needs may also change under different environmental conditions, such as weather, season, and temperature. This isn’t an issue for indoor setups that have a controlled environment, but it is something to consider if your hydroponics system is outside.
The nutrient solution must be kept at a steady temperature. The ideal is 70 to 78 degrees Fahrenheit. This is more of a concern for outdoor systems that are exposed to fluctuating temperatures. For winter, you can buy miniature water heaters that go inside your reservoir to keep the nutrient solution warm. For summer, keeping the reservoir in a shaded area and periodically topping it off with cool water will help keep it from getting too hot.
Premade vs. Homemade
You can either buy a premade nutrient solution or formulate your own. Small farms and hobbyists generally purchase premixed liquid or powder concentrates that are added to water. Large-scale farms generally mix their solutions to suit the specific needs of the plants that they are growing, using bulk concentrates of the individual chemical compounds.
Even for small farms and hobbyists, mixing your nutrient solutions can be helpful to create large quantities. These can be stored to last for weeks at a time. There are several benefits to each method of supplying nutrients to your plants:
Best for small farms and hobbyists
Easier to use
Requires fewer materials
Best for large-scale farms
Customizable to specific nutrients
Can be mixed in large quantities or on an as-needed basis
Using Premade Nutrient Solutions
Premixed concentrates usually come in two separate bottles: one for macronutrients and one for micronutrients. They are separated because some concentrated elements are incompatible with each other and cause precipitation when they are combined. Once diluted, they do not form precipitates and can be used together without issue. Some manufacturers have developed single solutions that hold the incompatible nutrients in a chemical complex so that they do not mix.
For hydroponics, twin- or triple-pack solutions are usually the best options. They are simple to mix and only require a few materials. Here’s how to prepare premixed concentrates of nutrient solutions:
- Step 1: Gather a container in which to mix the solution, a dedicated measuring cup, and a stirrer. Choose a container that is appropriately sized based on the mixing instructions for your specific concentrate. If your container has a lid, you can shake the mixture without using a stirrer.
- Step 2: Measure the concentrate based on its instructions. For example, the solution may be 3.5 millileters (mLs) of concentrate per liter of water, or it may be 1 ounce of concentrate per gallon (it varies among manufacturers). It’s important to dilute the solution accurately to ensure that your plants receive the right concentration of nutrients.
- Step 3: After mixing your solution, let it sit for a few minutes and settle. Check the pH of the solution and adjust as necessary. You can even measure the number of drops of the product pH Up or pH Down needed every time you mix your solution and add that amount to the water before mixing in your concentrate.
- Step 4: Feed the plants by adding the solution directly to the water of hydroponic plants.
Depending on the size of your system—for example, a large-scale Ebb and Flow setup—you may want to mix your nutrient solution in very large quantities. Fifty-five-gallon drums make ideal mixing containers for large systems, storing enough nutrient solution to replenish your reservoir for weeks. For smaller systems, or if you do not have space for a large mixing container, it is perfectly OK to mix your solution on an as-needed basis.
Hydroponics Systems and Principles of Plant Nutrition: Essential Nutrients, Function, Deficiency, and Excess. Penn State Extension
Hydroponics Systems: Nutrient Solution Programs and Recipes. Penn State Extension