NPK isn’t some trendy Gen Z abbreviation circulating on TikTok; it actually stands for nitrogen, potassium, and phosphorus—the cornerstone of nutrients for developing cannabis plants. NPK and cannabis are a fundamental dynamic for optimal results from your cannabis harvest.
There’s a lot of information available regarding the best NPK ratio for cannabis; however, growers obtain the most reliable results when they follow the guidance of peer-reviewed research and experienced cultivators.
Growers should dial in the best NPK ratio for cannabis during different growth cycles of the plant. The right balance helps cannabis grow vigorously and produce high-quality harvests. In this article, we not only discuss the best NPK ratios for cannabis cultivation, but also the ideal ratios for different cycles of growth.
Cultivators use a lot of different compounds and products to maintain the pH balance of their cannabis plants. Growers who understand the importance of NPK cannabis cultivation ratios also like to introduce other nutrients into the mix, depending on where on the pH scale the levels need to be. Nutrient solutions do well in hydroponic grows, while organic sources are used in traditional indoor and outdoor soils.
Nitrogen is an essential part of chlorophyll, so it directly affects plant size, particularly of flower buds. Hydroponic nutrient solutions include synthetic nitrogen sources, such as calcium nitrate and potassium nitrate.
Organic fertilizer sources provide beneficial microbes. These organic nitrogen sources include:
Phosphorus strengthens roots, boosts growth, and improves disease and mold resistance. This nutrient provides all of those factors, as well as contributes to flower and trichome development. Cultivators can add bone meal, bat guano, and similar materials as organic phosphorus sources.
Potassium supports osmosis and photosynthesis, providing benefits during the critical developmental stage of vegetation and increasing flower mass during flower bloom. Organic sources include kelp meal, wood ash, alfalfa meal, and even banana peels!
Secondary macronutrients like calcium play an important role during all growth stages, despite N, P, and K garnering all of the attention. Synthetic nutrients are available, while organic sources include:
Magnesium’s role during photosynthesis and nutrient transport can’t be understated. There are several organic cannabis soil nutrients containing magnesium available to cannabis growers, including dolomite lime, epsom salt, kelp meal, and compost.
Growers use smaller amounts of sulfur compared to other cannabis nutrients like NPK; however, it still supports photosynthesis, chlorophyll production, and terpene synthesis. The source of sulfur can be found organically in epsom salt, kelp meal, alfalfa meal, and compost.
Iron maintains growth vigor, especially during the vegetative stage. Roots, hormones, and enzymes all benefit from sources of iron that include chelated iron, blood meal, fish meal, alfalfa, and compost.
Plants use manganese in small amounts to boost health and reduce stress that can cause cannabis plants to produce lower-quality harvests. Organic sources of manganese include compost, kelp meal, greensand, and volcanic ash.
Zinc is another micronutrient that’s also super important for the internal development of cannabis plant enzymes, hormones, and growth regulation and development. This nutrient can be found in manure/compost, fish meal, kelp meal, and basalt dust.
Cultivators have several different ways to provide cannabis plants with nutrients, including NPK and others. Fertilizers, including these nutrients, usually fall under several different categories.
The importance of maintaining a proper pH level of the growing media will determine much of how your weed plant fares on its long journey to harvest. Each NPK cannabis ratio listed below is in order as N–P–K for each growth stage.
Soil slowly releases nutrients while supporting microbial activity for increased vigor and health. Soil-based cultivation often includes organic sources of NPK cannabis nutrients.
READ: Best Fertilizers for Indoor Cannabis Cultivation
Soilless growing media like coco coir are great for increased water and air retention, but not nutrients. A continuous nutrient uptake is needed to maintain efficient balances during each cycle of growth.
Hydroponic cultivation allows nutrients to be received courtesy of water with no soil or grow media buffer. Adjusting NPK in soil-grown cannabis doesn’t require as much control compared to hydro grow.
Choosing the right cannabis fertilizer isn’t always so easy with so much different information out there, combined with a multitude of available options. Anyone having difficulty making the right decision isn’t alone—here are a few practical tips.
Growers must supply proper nutrition for cannabis plants for successful bud-laden harvests, all the way from just a little seed or clone. Cannabis cultivators need to maintain a proper balance of nutrients to support proper development and ideal pH levels.
The NPK ratio for vegetative stage cannabis development is completely different than when in flower, for example. Simple adjustments like that ultimately make the difference between spending precious time, money, and energy on a successful harvest or a dud.
Cannabis cultivators seeking the best NPK ratio for cannabis soil experience a slower metabolism of nutrients due to the microbial content. The following summary of NPK ratios provides more detailed NPK ratios for each stage of growth:
Many experienced growers enjoy a soil mixture consisting of 1 part peat-based soil for optimal loaminess, 1 part coco coir for optimal water retention, 1 part vermiculite to ensure optimal drainage, and 1 part compost to add beneficial nutrients and microbes.
The best NPK ratio for cannabis depends on what type of grow medium you use, as well as the specific stage of development your plants are in.
Soil, soilless, and hydroponic ratios can also vary depending on the climate and environment for cultivation. Many growers can’t go wrong with any of the ratios listed above, according to each of these different types of growing media.
Big Bud nutrient solution is a flowering booster that provides ideal ratios of phosphorus and potassium, with minimal nitrogen content in a 0–2–3 ratio. Big Bud solution is used for hydroponic grows.
Cultivators must supply macronutrients and micronutrients throughout every growth stage. Macronutrients include:
Micronutrients include:
Cannabis plants in the flowering phase receive a different ratio compared to the vegetative stage. The NPK ratio for flowering cannabis eventually reduces nitrogen input to essentially nothing. Growers usually follow a 1–3–2 ratio at first during flower, then 0–2–3 later on during the flowering phase.
Is a 3:1:2 fertilizer good or does it HAVE to be 3:1:1? Growing Northern Lights Auto Feminised in potting mix and Im sure the Miracle Gro 20-20-20 is good for tomatoes but I’m not growing tomatoes. I’m growing indoor/outdoor with full Florida sun for 8-10 hours then another 8 hours under a red spectrum lamp. Any help appreciated.
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