Understanding nutrients in cannabis has a simple complexity to it. Simply speaking, it’s a matter of getting the right type of nutrient to the plant at a particular time. For example, “N-P-K” is a rating you will see on many essential nutrient bottles: N for Nitrogen, P for Phosphorus and K for Potassium; these are the basics. But the complexity comes in as you take the basics and tailor them to make them work for your grow and your priorities.
Most professional growers have a favorite brand or mix of brands. But you need to do your homework, ask questions and learn from trial and error as to what nutrient solution works best for you. For consistency, it is important that you do not change brands mid-grow. A shift mid-flower can cause problems, depending on organic and non-organic compounds. It is best practice to wait, then change at the beginning of each new cycle.
Tips for adding nutrients
First, start with water that has been filtered through a reverse osmosis system and is ready for pH, parts per million (PPM) and temperature tests. There are some great combined test units on the market. Knowing where you begin with your water’s base levels helps you add as much benefit to the water as possible. pH will not be a factor until after you have added your nutrients. Starting with a PPM as close to zero is best for most systems.
The amount of nutrients you add affects the total PPM of additives to your water. The balance of macro and micronutrients will change your pH overall. Bringing the PPM to a high—but not too high—point allows your plants to uptake and use the correct nutrient at the right time. Some plants can handle a water PPM of over 1300, and some like to stay in the 900 PPM range. Simple research on your chosen strains, nutrient line and a slow, gradual increase in each watering PPM level will let you know how high you can go.
Second, more is not always better. Your plants will tell you what they like and don’t like. Water temperature and your added air stone system will work together to help the nutrients more evenly blend into the water and eventually into your soil.
Third, choose a nutrient that’s higher in nitrogen for early growth and feeding. Cannabis plants love nitrogen and will use it quickly once they’re past seedling or clone stage. But use nutrients sparingly when you are dealing with new plants, seedlings and clones; if you overuse nitrogen on young plants, you can burn them.
Fourth, as your plants reach the state of readiness for flowering, lower the nitrogen and begin to raise the phosphorus. This shift will allow the flowers to form and feed on phosphorus. Potassium is beneficial through the entire grow period and the flowering cycle. The rule of high nitrogen for vegetative and high phosphorus for flowering always applies, no matter what nutrient line you choose.
The closer your cannabis flowers are to finishing, the more phosphorus they will use. It is OK to load them up for the last few weeks, but keep a calendar and know when to stop all feedings and let the plant flush. This flushing will give the plant a chance to use its stored nutrients, leaving you with flowers that have little to no trace of additives. Flushing should take place for the last few weeks to ensure the plant has a pure taste and is free of nutrients. It is best to flush with water that has been filtered and pH-balanced with no nutrients added.
Fifth, there are many choices for nutrient options, such as Botanicare Pure Blend, FoxFarm, General Organics and many others. Remember to start light and not full strength, take notes, and pH your water each time you use it. When bringing the pH to your desired level, always give the pH additives a few hours to balance and level off. This waiting period will save you from burning plants or damaging roots. Also, pH imbalances can cause root lock and other nutrient uptake deficiencies.
Finally, if you have built your soil in a way that includes many organic micronutrients, you will need to add them to your water schedule only every few cycles to keep them enhanced. The cannabis plant loves vitamin B, and products like Superthrive can be added to every watering in higher than average amounts. Superthrive is recommended to help make dense and hearty buds; it is also ideal for vegetative growth.
Light, airflow, temperature, humidity control and nutrients are the basics of every good garden. Understanding this basic yet complex symbiotic relationship will allow you to become a well-versed, advanced professional grower.
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