Hydroponic nutrient liquids are designed to provide all of the nutrients that plants need for healthy growth. Each commercial nutrient manufacturer has its own proprietary recipe, but they all contain the necessary nutrients for plant nutrition. Sixteen different nutrients have been identified as essential for plant life. The sources of each nutrient varies depending on the manufacturer and whether the nutrient solution is a natural organic solution or from a chemical source. Carbon is the only necessary nutrient that is not included in the nutrient solution. Plants get carbon from taking in carbon dioxide.
The bulk of the nutrient solution is water. Plants absorb water from the nutrient solution to supply hydrogen and oxygen for the plant. The water source needs to be clean and free of excess dissolved solids with a pH in the 5.5 to 7.0 range.
Nitrogen, phosphorus and potassium are the primary nutrients used by plants and are the nutrients provided by most fertilizer formulas. Plants need these nutrients in large amounts. The ratio of these nutrients changes for different plants and during different life phases. Nitrogen is necessary during heavy vegetative growth phases. Potassium is required in the photosynthesis process throughout the plant life. Phosphorus encourages germination and plant growth. It encourages plants to flower and make fruit.
Calcium, magnesium and sulfur are needed by plants in smaller amounts. Calcium is a necessary part of the plant’s cell wall. Magnesium is necessary for photosynthesis, the main energy source for plants. Sulfur is necessary in the makeup of plant proteins and vitamins.
Micronutrients are needed in lesser amounts, but are vital to plant health. Iron, copper, chlorine, boron, manganese, zinc, and molybdenum are needed in very small amounts. In large amounts these micronutrients can be toxic to plants.
Other Beneficial Nutrients
These nutrients are not included in the necessary nutrients for plant life, but are considered beneficial and are sometimes included in nutrient solutions. Cobalt, silicon, vanadium and sodium are considered beneficial for some, but not all, plants. Nickel is considered essential by some because some grains will not germinate without it and it participates in the nitrogen fixing cycle of legumes.
The Role of pH
The pH of the nutrient solution is very important and additional acid or base is often added to the nutrient solution to balance it. If the nutrient solution is too acid or too basic, the plant will not be able to uptake or use some nutrients, even though they are present in the solution. Some nutrients will not dissolve or will fall out of solution if the pH is not in an acceptable range. For most plants, a pH between 5.5 and 6.5 is desirable.