Hydroponic gardening removes the soil, relying entirely on a prepared water solution to deliver all necessary macro and micronutrients directly to the roots. These hydroponic nutrients are specialized, water-soluble mineral salts. The success of a soilless system depends on the precision and consistency of this solution. Correctly mixing these concentrated salts is crucial for preventing nutrient deficiencies, toxicities, and chemical precipitation. This guide provides instructions to accurately prepare and manage the solution, ensuring a healthy foundation for plant growth.
Essential Supplies and Pre-Mixing Preparation
The quality of the starting water must be established, as it forms the basis of the nutrient solution. Tap water often contains non-nutrient minerals like sodium and chloride, or chemicals such as chlorine, which can be toxic to roots. Hard water, high in calcium and magnesium, can also disrupt the final nutrient balance and clog system components. Many growers prefer reverse osmosis (RO) or distilled water, which provides a blank slate with a total dissolved solids (TDS) reading near zero.
Accurate measurement tools are necessary to achieve the correct concentrations. Essential supplies include calibrated measuring cups or syringes for concentrates, a clean mixing container, and a long-handled, non-reactive stirring tool. All mixing equipment, especially the reservoir, should be thoroughly cleaned to prevent contamination from previous batches. Contamination could chemically react with new nutrients or introduce pathogens.
Step-by-Step Guide to Mixing Nutrients
The physical act of combining nutrient components is governed by preventing precipitation. Precipitation, often called “nutrient lockout,” occurs when incompatible elements are mixed in concentrated form, bonding and falling out of solution as an insoluble solid. Once precipitated, these elements are unavailable to the roots and can clog pumps and emitters.
To avoid precipitation, always fill the mixing container with approximately 75% of the total water volume before adding any concentrates. If using a multi-part system (like a two-part A and B formula), never mix the concentrated parts directly. The primary incompatibility is between calcium in one part and sulfates or phosphates in the other.
Add the first part of the base nutrient (often Part A) to the water and stir until completely dissolved. Repeat this process for the second part (Part B), stirring thoroughly after each addition to ensure full dilution. Supplements, such as bloom boosters or Cal-Mag, should be added only after the primary base nutrients are fully incorporated. Silica, being highly reactive, should be added first and allowed to stabilize for several minutes before introducing other nutrients.
Calibrating Your Solution (pH and EC/TDS)
Once nutrients are mixed, the solution must be measured and calibrated. Electrical Conductivity (EC) or Total Dissolved Solids (TDS) is measured first to determine the concentration of dissolved mineral salts. EC measures the solution’s ability to conduct electricity, correlating directly to the total ion content. TDS is a calculated conversion of that reading, often expressed in parts per million (ppm).
Measuring Concentration (EC/TDS)
The target EC/TDS range depends on the plant species and its growth stage. A general range of 1.2 to 2.5 mS/cm (600 to 1250 ppm) is typical for many crops. If the reading is too high, add plain water to dilute the solution. If the reading is too low, add a small amount of the full nutrient mix until the target is reached.
Adjusting Acidity (pH)
After adjusting concentration, the pH (measure of acidity or alkalinity) must be checked. The optimal pH range for most hydroponic plants is slightly acidic, generally falling between 5.5 and 6.5. This range ensures that all macro and micronutrients remain soluble and available for root uptake. A digital pH meter is the most reliable tool for this measurement.
If the pH is outside the target range, use an acid-based solution (pH Down, typically phosphoric or nitric acid) or a base-based solution (pH Up, typically potassium hydroxide) for correction. Add these adjusters very slowly and in small increments, followed by thorough stirring. Wait 15 to 20 minutes after adding the adjuster before taking a final reading to allow the solution to fully stabilize.
Maintaining and Refreshing the Nutrient Reservoir
Proper management of the nutrient reservoir ensures continuous plant access to nutrition. The solution should be completely replaced every 7 to 14 days, even if the EC and pH appear stable. This prevents the buildup of unused elements or harmful organic byproducts. Plants selectively absorb nutrients over time, altering the balance of the remaining solution and leading to imbalances.
Between full changes, the water level drops due to plant uptake and evaporation. This lost volume should be topped off with water that has been pH-adjusted to match the reservoir’s target. If the EC reading is rising due to evaporation, use plain water for the top-off; if the EC is dropping, use a lightly diluted nutrient solution instead.
Monitoring the solution temperature is also important, with an optimal range between 68°F and 72°F (20°C and 22°C). Temperatures above this range reduce dissolved oxygen, which stresses roots and promotes harmful anaerobic pathogens like root rot. When disposing of the old solution, do not pour it near waterways; it can often be diluted and used to water outdoor or potted plants.