By Dr. Who
When it comes to growing in soil, you have many options for nutrients. You should always take into consideration your growing medium when choosing your nutrient. Different brands of soils have different compositions and nutrient requirements.
There are basically two different soils—inert and non-inert. Inert soils such as sphagnum peat moss and coco coir (coconut husks) that are commercially available contain no nutritional value. This means that you must supply every nutrient and micronutrient that the plant needs or you will get nutrient deficiencies in your plants very quickly. Non-inert soils such as potting soils usually contain composted matter, which is rich in macro- and micronutrients and alleviate some of the possible nutrient-deficiency problems.
Macronutrients are nitrogen (N), phosphorus (P) and potassium (K). These are the building blocks of all plants. Plants use large quantities of these nutrients, so soils usually run out of these very quickly. The percentages of these nutrients are typically labeled on each fertilizer. A nutrient that is labeled “5-6-7” would contain 5 percent nitrogen, 6 percent phosphorus and 7 percent potassium.
Secondary nutrients are calcium (Ca), magnesium (Mg) and sulfur (S). Plants use these in smaller quantities. Non-inert soils usually contain sufficient quantities of these nutrients.
The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). Plants use these in small quantities, but they are still very important. You can get micronutrient deficiencies very easily by not choosing a good quality plant food.
Marijuana uses large amounts of nitrogen during the growth, or vegetative, phase. This is when the plants are first starting out, producing most of the leaves and “bushiness” that will determine the size of the plant during maturation. This phase is determined by light cycle. If you are giving your plants about 18 hours of light per day, they will stay in the vegetative phase. The longer you keep the plants in this phase, the larger they will finish. You want to use a high-nitrogen fertilizer during this phase.
Budding and flowering plants use more potassium and phosphorus during the bloom period, when cutting your lights back to 12 hours on and 12 hours off induces the plant to bloom. Feeding them a quality bloom mix with high phosphorus and potassium levels will give them the nutrition that they need.
It is always best to feed your plants a good quality nutrient with a full micronutrient set. The plant foods that are available at your local home improvement store give plants all of the macro- and secondary nutrients that you need, but are usually lacking in the micronutrients. Some specialty plant foods contain all of the micronutrients that your plants will need all throughout the growing cycle, thus ensuring a bountiful crop.
DR. WHO is a Southern California expert in plant cultivation. Reach him at firstname.lastname@example.org.