While cannabis plants require very low concentrations of mineral and non-mineral elements to thrive, these elements are still vital to the overall health and growth of the plant.
Many of the premium potting soils marketed for growing cannabis are actually soilless blends. Most indoor cannabis growers are growing hydroponically, even if they’re using buckets of potting soil and hand watering each plant. For this reason, the vast majority of the nutrients sold specifically for cannabis cultivation are hydroponic nutrients. These products are comprised of concentrated mineral salts, usually in liquid form but sometimes as powders, that are to be diluted in water to a level that is suitable for the plant.
What sets soil apart from hydroponic media is the presence of non-inert organic matter like humus, compost, manure, and worm castings that contain many macro and micronutrients. Much of the nutritional value in these substances is locked up in non-soluble form, however, and must be processed by soil-dwelling microbes and fungi in order to be of use to the plant. Non-organic nutrients designed for soil growing are less common at the grow shop because they can quickly build up in the soil, harming the soil life as well as preventing the uptake of water and nutrients by the root system.
Organic fertilizers and nutrients for cannabis are far more forgiving; they usually contain less immediately soluble nutrients and more elements that are beneficial to soil organisms. The first-time grower who decides to use soil as their medium would be well advised to stick to organic fertilizers and nutrients.
Learn more about cannabis plant nutrition at Leafly.com.