Nutrient Solution

Most plant problems are a result of using the wrong amount of fertilizer. Too little and your plants are weak and underfed, too much and you can burn the plant and even kill it. In most cases, it is a judgment call and requires constant monitoring and adjusting as the plant matures. This section contains general guidelines that apply to fertilizing most types of plants.

Hydroponic nutrient solutions are sold in concentrated form and added to your indoor garden's water supply at a certain ratio. The ideal concentration for your hydroponic solution is about 150-600 parts per million (ppm). For most plants, you can narrow that range down to 300-400 ppm. They are typically sold in two or three parts because some of the nutrients cannot be combined directly. Always mix each part of your nutrient solution directly into the water, never into another nutrient type.

How Much Hydroponic Nutrient Solution?

Plants require different proportions of nutrients during vegetation and flowering. Modern nutrient products are far more advanced than their earlier counterparts and now allow precise adjustments based on growth stage. Most hydroponic nutrient solutions are sold in a "growth" or "grow" formula for the vegetative growth phase and a "bloom" or "flower" formula for the flowering phase of the growth cycle. You should at least switch to the bloom formula because your yield will increase exponentially if you can max out your plant's capacity during the flowering stage.

A weak nutrient solution should be used for plants in poor growing conditions, such as low light, overheated gardens, and root-bound or crowded plants. It is also ideal for newly rooted cuttings and plants in the process of being transplanted or in transition between growing cycles.

Regular strength solution is fine for normal, healthy plants in ideal growing conditions. In rare conditions, you may be able to increase the fertilizer strength to capitalize on the efficiency of your garden. This only works if you have high quality lighting, ventilation, and CO2 production that will allow your plants to grow fast enough to handle the extra feedings. Always make sure to increase the fertilizer strength gradually to avoid burning the plant.

In addition to the basic types of hydroponic nutrient solution, there are also various additives you can purchase to boost your plant's growth. Keep good records in your grow log of what additives are used, when they were applied, and the results (good or bad). This will give you a good reference guide on what worked and what didn't work for your future grows. Flush your hydroponic system immediately if you see any signs of an adverse reaction.

How to Measure Hydroponic Nutrient Solutions

The concentration of nutrients in your hydroponic nutrient solution is usually measured by the electrical conductivity of the dissolved minerals in the water. The unit of measure is parts per million (ppm), but this only measures the total conductivity of the solution, not the relative strength of the various minerals. This is another reason why most hydroponic nutrient solutions are sold as a mix of 3 parts instead of by individual nutrient. Once you have the correct mix between the parts, it is easy to add to or dilute the solution to achieve the correct conductivity.

Over-use of Hydroponic Fertilizer

If you see any signs of over-fertlization, you should immediately flush out your growing medium to allow the plant to recover before further damage is done. Use only clean water until the plant shows symptoms of nutrient deficiency. Then you may resume your normal feeding schedule. Depending on your hydroponic system, flushing may require top down watering to completely clean out the medium.

Another good time to do a complete flush of the plant and medium is around 2 weeks before your expected harvest date. That will help prevent the vegetables from tasting like your hydroponic nutrient solution.

Primary Hydroponic Nutrients

• Nitrogen (N)
• Nitrogen is the most important nutrient for leaf and stem development. Most plants need more nitrogen during the vegetative growth phase. Hydroponic nutrient solutions with "grow" or "flower" in their name usually contain an extra boost of nitrogen for vegetating plants. Nitrogen deficiency is the most common plant problem found in hydroponic growing systems. Soft, weak plants and yellow leaves are signs of nitrogen deficiency.
• When plants are in transition between growing phases, it may be better to use only a half-strength nitrogen mix in your solution. This will prevent your plant from stretching while it is switching its energy over to flower development. Resume feeding with your regular mix of hydroponic nutrients after the plant is fully into flowering stage.
• Phosphorus (P)
• Phosphorus is crucial for root and flower development. Slow and/or stunted growth could be a sign of phosphorus deficiency. Phosphorus becomes even more important during the flowering stage. Most "Bloom" type formulas contain a breakdown of 0-50-30, which means they contain no nitrogen and much higher levels of phosphorus and potassium.
• Potassium (K)
• Potassium is different from the other two hydroponic nutrients in that it doesn't feed the plant directly in any stage of growth. It regulates and aids the intake of the other primary and secondary nutrients. Without sufficient potassium, your plant may experience irregular growth and increased susceptibility to disease and pests. You should give less potassium during flowering because it inhibits fruit production.

Secondary Hydroponic Nutrients

• Calcium (Ca)
• Calcium is crucial because it filters and aids the absorption of many other nutrients. Calcium is a base, which can help raise pH if needed. It is most often used during vegetation, with only small amounts still used during the flowering stage.
• Magnesium (Mg)
• Magnesium is used by the plant to produce chlorophyll during photosynthesis. Magnesium deficiency shows during flowering as yellowing leaves while the leaf veins are still green.
• Sulfur (S)
• Sulfur is used only in small amounts by the plant. Sulfur deficiency is shown when your new leaves turn yellow.
• Iron (Fe)
• Iron is also only used in small amounts. Iron deficiency appears very similar to sulfur deficiency, with the new leaves turning yellow. Be sure to also check your pH if you see signs of iron deficiency because high pH can impair the plant's ability to absorb iron.
• Molybdenum (Mb)
• Molybdenum aids the intake of nitrogen and is used in the conversion of nitrate to ammonium.
• Boron (B)
• Boron is used for carbohydrate transport in the phloem, but may or may not be required. Boron is not usually found in regular soil and must be supplemented if needed. Be very careful not to over use as excess boron can kill the plant.