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Hydroponic & Water-Soluble Fertilizer Guide: Nutrient Solutions & Ratios
Hydroponic and water-soluble fertilizer guide: nutrient solutions, EC/PPM targets, pH management, and crop ratios for soilless growing.
What Is It ?
Hydroponic and container growing eliminate soil from the equation entirely, which means every single nutrient your plants need must come from the fertilizer you dissolve in water. There is no soil biology to buffer mistakes, no organic matter to slowly release nutrients on a forgiving timeline, and no mineral reserves to fall back on when your solution runs low. This makes fertilizer selection and management the single most critical skill in soilless growing — more important than lighting, more important than temperature, more important than variety selection. Plants grown in water, perlite, coco coir, or other inert media depend on a complete nutrient solution that provides all essential elements in the correct proportions and at the right concentration. The three primary nutrients — nitrogen, phosphorus, and potassium — must be supplied in water-soluble forms that dissolve completely without residue that clogs drip lines and emitters. Equally important are secondary nutrients like magnesium and sulfur, plus trace elements including iron, manganese, and zinc. Old Cobblers Farm's Wicked Growth 19-19-19 is a fully water-soluble formula that dissolves completely for clean nutrient delivery, and combined with Wicked Organics Epsom Salt for magnesium supplementation, it provides the foundation for productive soilless growing. This guide covers everything from basic EC and pH management to crop-specific nutrient ratios and troubleshooting common deficiency symptoms in soilless systems.
Why Water-Soluble Fertilizers Are Different From Granular
Standard granular fertilizers designed for soil application often contain insoluble fillers, slow-release coatings, or nutrient forms that require microbial breakdown to become plant-available. These products are engineered for soil environments where insoluble materials gradually dissolve through weathering and microbial activity over weeks and months. In a hydroponic system, these properties become serious problems: insoluble materials clog drip lines, emitters, and spray nozzles. Slow-release coatings that work perfectly in soil do nothing in a recirculating reservoir. Nutrient forms that depend on soil bacteria never become available because there is no soil biology to process them.
Water-soluble fertilizers must dissolve completely in water, leave no residue, and provide nutrients in immediately plant-available ionic forms. When you dissolve Wicked Growth 19-19-19 in water, the nitrogen, phosphorus, and potassium are instantly in the forms that plant roots recognize and absorb: nitrate and ammonium for nitrogen, phosphate for phosphorus, and potassium ions for potassium. No waiting, no microbial processing, no insoluble residue.
Old Cobblers Farm's Wicked Growth 19-19-19 is a fully water-soluble formula designed for three applications: hydroponic systems, container feeding, and foliar spraying. Its balanced 1:1:1 ratio provides equal parts of all three primary nutrients, making it a solid foundation for most crops during vegetative growth. At 1 tablespoon per gallon of water, it provides a moderately concentrated feeding suitable for most established plants. At half-tablespoon per gallon, it provides a gentle feeding suitable for seedlings, newly transplanted starts, and sensitive crops.
Understanding EC and PPM: Measuring Nutrient Concentration
In soil gardening, you measure fertilizer by weight per area — pounds per 1,000 square feet. In hydroponics, you measure fertilizer by concentration — how much dissolved nutrient is in each gallon of solution. The standard measurement tool is electrical conductivity (EC), which measures the total dissolved salts in your nutrient solution. Pure water has an EC near zero. Adding fertilizer increases EC proportionally.
Most hydroponic crops perform best at EC 1.2-2.5 mS/cm (millisiemens per centimeter), which translates to roughly 600-1,250 ppm (parts per million) on the 500 scale. This range provides enough nutrient concentration for vigorous growth without the osmotic stress that occurs at higher concentrations.
Different crops have different optimal EC ranges based on their nutrient demands and salt tolerance. Leafy greens like lettuce, spinach, and herbs prefer the lower end: EC 1.2-1.8. Their relatively modest nutrient demands and sensitivity to salt stress mean they perform best with lighter feeding. Fruiting crops like tomatoes, peppers, and cucumbers prefer higher concentrations: EC 2.0-2.8. Their heavy nutrient demands during fruit production require more dissolved nutrients. Herbs like basil, cilantro, and parsley fall in the middle: EC 1.4-2.0.
Start at the low end of the recommended range and increase gradually based on plant response. Leaf tip burn — brown, crispy leaf edges — indicates the solution is too concentrated. Pale, slow growth with thin stems suggests the solution is too dilute. Adjust by adding more Wicked Growth 19-19-19 or diluting with plain water.
pH Management in Hydroponics
pH management is even more critical in hydroponics than in soil because there is no soil buffer to moderate swings. In soil, clay particles and organic matter absorb excess hydrogen ions and release them gradually, preventing rapid pH changes. In water, there is no buffer — pH can shift dramatically with nutrient uptake, water evaporation, and microbial activity.
Most hydroponic crops perform best at pH 5.5-6.5, with the sweet spot at 5.8-6.2 for most vegetables. This slightly acidic range keeps all essential nutrients in plant-available forms simultaneously. At pH below 5.0, calcium and magnesium become less available and some micronutrients reach toxic concentrations. Above 7.0, iron, manganese, zinc, and phosphorus precipitate out of solution — literally becoming insoluble particles that cannot be absorbed by roots, clogging systems and starving plants.
Check pH daily using a calibrated digital pH meter. Expect pH to drift upward as plants absorb nutrients (they take up more anions than cations from most balanced solutions, leaving excess hydroxide ions that raise pH). Adjust downward with pH-down solutions available at hydroponic supply stores. The need for frequent pH adjustment is normal — it is a sign that plants are actively absorbing nutrients.
How To Store
While Wicked Growth 19-19-19 provides the primary NPK foundation, most hydroponic crops benefit from supplementation to fill specific nutrient gaps.
Wicked Organics Epsom Salt (Magnesium Sulfate) is a standard hydroponic addition at 1-2 grams per gallon (roughly one-quarter to one-half teaspoon). It supplies magnesium — the central atom of every chlorophyll molecule and therefore essential for photosynthesis — and sulfur, which is required for amino acid and protein synthesis. Epsom Salt dissolves instantly and completely in water with zero residue, making it ideal for reservoir addition. It does not significantly affect pH or interact negatively with other nutrients in solution.
For crops showing potassium deficiency during heavy fruiting — leaf edge browning, poor fruit color, uneven ripening — a small addition of Wicked Growth 0-0-60 Muriate of Potash can boost potassium levels. Use sparingly: potassium chloride has a high salt index and can raise EC quickly. Start with one-eighth teaspoon per gallon and check EC before adding more. This targeted supplementation is most commonly needed in tomatoes and peppers during peak fruit production when potassium demand exceeds what balanced 19-19-19 provides.
If nitrogen demand is especially high during vegetative growth — common in leafy greens and herbs harvested repeatedly — a small addition of Wicked Growth 46-0-0 Urea at one-eighth teaspoon per gallon boosts nitrogen without adding proportional P and K. Monitor EC closely and adjust.
Wicked Organics Kelp Meal (1-0-2) can be brewed into kelp tea for hydroponic supplementation. The natural cytokinins, auxins, and trace minerals in kelp stimulate root development, improve stress tolerance, and fill micronutrient gaps that pure synthetic solutions may lack. Steep one tablespoon of kelp meal per gallon of water for 24-48 hours, then strain thoroughly through fine cheesecloth or a paint strainer to remove all solids that could clog lines. Add the strained extract to your reservoir at each solution change.
Supplementing Your Solution With Old Cobblers Farm Products
Change your nutrient solution completely every 1-2 weeks rather than simply topping off with more concentrated solution. As plants selectively absorb nutrients at different rates, the remaining solution becomes imbalanced — some nutrients accumulate while others are depleted. Topping off with fresh concentrated solution masks this imbalance, potentially leading to toxicity of over-accumulated nutrients and deficiency of over-consumed ones. A complete change resets the ratios to their correct proportions.
Between complete changes, top off with plain pH-adjusted water to maintain volume and concentration. Plants consume water faster than nutrients through transpiration, so the solution gradually becomes more concentrated as water evaporates and is taken up by roots. Topping off with plain water counteracts this concentration drift and keeps EC stable.
Water quality matters enormously. Hard water with high calcium and magnesium content can supply a significant portion of these nutrients, which means your Wicked Growth 19-19-19 solution combined with hard tap water may provide excess calcium and magnesium. Test your source water and account for its mineral content when designing your nutrient program. Very hard water may require pre-treatment with a reverse osmosis system. Soft water or RO water will need extra Epsom Salt supplementation since there is no background mineral content to start with.
Water temperature should stay between 65-72 degrees Fahrenheit. Cold water holds more dissolved oxygen, which roots need for respiration, but extremely cold water can shock roots and slow nutrient uptake. Warm water above 75 degrees holds less oxygen and promotes the growth of root-rotting pathogens like Pythium. An aquarium heater or chiller can maintain optimal temperature in reservoirs.
Nutrient Solution Management Best Practices
You do not need a full hydroponic setup to benefit from water-soluble feeding. Container gardens, hanging baskets, window boxes, and raised beds with soilless media all respond exceptionally well to dissolved Wicked Growth 19-19-19 applied every 1-2 weeks during active growth. The principles of hydroponic nutrient management apply directly to any container growing situation.
Wicked Growth Hanging Plant Fertilizer (10-10-10) dissolved in water works specifically for hanging baskets and window boxes. These containers dry out and leach nutrients faster than ground-level pots because of increased air exposure on all sides, making frequent water-soluble feeding essential.
For container tomatoes, start with balanced 19-19-19 during vegetative growth. Once flowering begins, supplement with additional potassium using a small amount of 0-0-60 dissolved in the feeding solution. This shift from balanced nutrition to potassium-forward feeding mirrors the professional hydroponic approach to fruiting crop management — and it works just as well in a 5-gallon bucket on your patio as it does in a commercial greenhouse.
Troubleshooting Common Nutrient Problems
If leaves turn yellow starting with the oldest, lowest leaves and growth slows, nitrogen is insufficient — increase Wicked Growth 19-19-19 concentration or supplement with a small amount of 46-0-0 Urea dissolved in the reservoir. If leaf edges turn brown and crispy while interior leaf tissue remains green, potassium is low — add a small amount of Wicked Growth 0-0-60 dissolved carefully. If leaves yellow between the veins while veins stay green (interveinal chlorosis), the issue is usually magnesium — increase Epsom Salt supplementation. If new growth at the top of the plant is distorted, pale, or stunted while older growth looks fine, the problem is typically a micronutrient deficiency or pH out of range — check pH first, then consider kelp tea supplementation for trace minerals.