Nutrients are individual mineral elements that are synthesized to make fertilizers.
Cannabis uses several different nutrients that it absorbs mostly through its roots.
Primary macronutrients: Nitrogen (N), Phosphorus (P), Potassium (K)
Secondary macronutrients: Calcium (Ca), Sulfur (S), Magnesium (Mg)
Micronutrients: Zinc (Zn), Manganese (Mn), Iron (Fe), Chlorine (Cl), Boron (B), Copper (Cu), Molybdenum (Mo), Nickel (Ni)
There are organic and non-organic indoor fertilizers.
Non-organic fertilizers are formulated from mined minerals and synthesized to be highly water soluble. They flow well through hydroponic systems and they can be absorbed easily by plants roots. The disadvantage to these fertilizers is the mineral ingredients used to make them are mined in an environmentally destructive way.
Organic fertilizers use materials that are not mined destructively. For example, organic sources of potassium include wood ash and kelp meal, which can be acquired without adverse harm on the environment. The disadvantage of organic fertilizers is they can ferment in reservoirs and clog up hydroponic systems since they are not highly soluble. Use them when hand watering an indoor planting mix, not in hydroponic systems that use a reservoir or pumps to deliver the nutrient / water solution.
The most important nutrients for marijuana growth are the primary macronutrients: Nitrogen, Phosphorus and Potassium. The concentrations of these is usually displayed right on the front of the fertilizer bottle. A main priority of most fertilizers is to ensure adequate supply of these three main nutrients.
For marijuana, the ideal concentrations of Nitrogen, Phosphorus and Potassium is different for early growth (vegetative) and later stage of growth (flowering). When growing hydroponically indoors, a 2 step fertilizer system, 1 for vegetative and 1 for flowering, addresses these needs.
Along with the primary macronutrients, fertilizers usually also contain many secondary macronutrients and micronutrients.
Too much, or too little, nutrients can cause problems. Too much can cause nutrient burn and too little can cause defects and a reduced yield. Adding the ideal amount of fertilizer improves growth substantially.
The tap water you start with contains some dissolved minerals already, usually calcium and magnesium. Your plants will not do well with just small amounts of calcium and magnesium, so tap water alone is not good enough. Fertilizers add more nutrients and a wider variety of nutrients.
Typically, the nutrients in tap water is approximately 100 parts per million. You plants need 500-600 parts per million when they are young seedlings and clones, 800-900 parts per million in the vegetative (grow) phase, 1000-1100 parts per million during flowering (bloom) phase, and 400-500 ppm when they are being flushed at the end of their lifecycle.
Mixing instructions that come with fertilizers will tell you how much fertilizer to mix with water. For example, 10 ml for every litre of water. You can also measure nutrients in your water, expressed as parts per million, with a TDS digital reader. Following mixing instructions should get you in the ballpark of where you need to be, but using a TDS digital reader to measure parts per million is the most accurate way to measure nutrient levels.
If you are using a reservoir and pump to deliver nutrients to you plants, it is more important to use a TDS digital reader than if you are planting in a growing medium and watering manually. A growing medium can “buffer” nutrient swings, making accuracy less important. Buffering means the medium holds and stores nutrients if you add too many. If you add too many nutrients, the medium will just store the excess and release it later. In a reservoir and pump system, there is no buffer.
A TDS digital reader will tell you the exact parts per million in the water. You can monitor and adjust your reservoir to maintain an ideal level of nutrients. The benefit is superior growth because your plants will always have the ideal amount of nutrients.
Tap water with an excess of native nutrients is called hard water. If you are lucky, you do not have hard water. Hard water is a problem because it makes it impossible to feed plants properly. For example, lets say your tap water is already 800 ppm. This is already the correct concentration for vegetative growth. But all the dissolved solids in tap water are calcium and magnesium, and the plant needs other kinds of nutrients also, most notably Nitrogen. If you add more fertilizer to give your plants enough nitrogen, you may increase the volume of dissolved solids to a level that causes problems such as nutrient lockout (a condition that can occur when the dissolved solids are too high). With hard water, the grower is stuck between giving too many nutrients, or too few of the nutrients that the plants need.
If you have a serious hard water issue you need to use a reverse osmosis machine, or find another water source that is not contaminated. If you have a small issue, you need to be aware of the issue and factor it in to your calculations. For example, if you have 50 ppm extra hard water, you may want to set a target for vegetative growth at 850 – 950, rather than 800 – 900, to ensure adequate levels of the nutrients are available that you plant needs.
The chart below shows the ideal ppm (parts per million) of the most important nutrients in a hydroponic solution.
Normally you just measure the overall amount of nutrients in the solution, not the amount of the individual nutrients. This chart is here to help you expand your understanding. If you want to measure individual nutrients you will need a chemical testing kit to do it.
In the chart below strong light refers to sunlight and 1000 w HID.
|Nutrient||Vegetative (Grow)||Flowering (Bloom)|
A simple two-step system
This is an example of an affordable basic two-step fertilizer system. It is a general purpose fertilizer that is intended to work for a wide range of plants, both for indoor and outdoor use.
For growing marijuana indoors, you could use the Foliage pro during vegetative growth and the grow formula during flowering.
The nitrogen, phosphorus and potassium levels on the Foliage pro is 9-3-6. The high ratio of nitrogen is good for vegetative growth.
The nitrogen, phosphorus and potassium levels on the bloom is 3-12-6. The high ratio of phosphorus and lower nitrogen is good for flowering.
These fertilizers also have secondary macro, and micro nutrients.
Another simple two-step system
This is an another example of a basic two-step fertilizer system. Note the differences in the nitrogen, phosphorus and potassium levels on this set compared to the example above. The part A for vegetative growth is 5-0-6. The part B for Flowering growth is 1-5-4. These levels are lower.
This fertilizer is designed specifically for hydroponics. Usually hydroponic systems use smaller containers, so the nutrients can’t spread out. Less nutrients is better when working with small containers because the nutrients are more concentrated around the plants roots.
A two-step organic system
Many products that are labelled organic are not actually organic because they contain mined nutrients. In order to be truly organic it has to be certified and contain only organic ingredients. This product is truly organic.
Organic products clog hydroponic systems and ferment in reservoirs, which is why most hydroponic fertilizers are not organic. You can use organic fertilizers indoors if you are hand watering.