You might have a lot of questions when it comes to your cannabis plants’ fertilizer: What are the differences between the different types of fertilizer? What is a granular fertilizer? What is a water-soluble fertilizer? What does slow-release, timed-release, and controlled-release mean? What is an organic fertilizer? Does the type of fertilizer affect my plant? What is the best fertilizer for a cannabis plant? If these questions sound familiar, then you’re in the right place.
Choosing a fertilizer can be a confusing. Choosing the right type of fertilizer requires knowing the cause of illness you want to fix on your cannabis plant or how you want to help your plants grow. There are two options available: liquid fertilizers and solid granular fertilizers. Knowing the positives and negatives of each type can help you choose what’s right for your grow needs.
Granular fertilizers are solid granules that need a while to dissolve or decompose before your plants can access their nutrients.
Granular fertilizers are meant to be worked into the soil or sprinkled around plants. They last 1 to 9 months, depending on the type. Because they must first break down before releasing nutrients, it usually takes watering and a few days to start seeing results. It’s often good to work them into the ground before planting.
You apply granular fertilizers dry — with a mechanical spreader or from a shaker container —and water them in. Fertilizer for lawns and gardens are often in granular form. They’re easier to control because you can see how much you’re using and where you’re dispersing them. There are two formulations of granular fertilizers:
- Quick-release — water-soluble nitrogen (WSN) — provide nitrogen to plants immediately. They generally last for 3 to 4 weeks, depending on the rainfall and temperature.
- Slow-release — water-insoluble nitrogen (WIN) — available in sulfur-coated varieties, which last for about 8 weeks, and polymer-coated varieties, which can last for about 12 weeks. The time estimates may vary depending on the amount of rainfall. You don’t need to apply these fertilizers as often, and they produce more even growth. In addition, burning caused by nitrogen is less of a concern with slow-release fertilizers.
There are also some natural fertilizers that are not organic, such as Greensand, which contains potassium, iron, calcium, and other nutrients. These are considered okay for organic gardening because they are not synthesized, but come from natural mineral-rich deposits in the earth.
Organic granular fertilizer, that does not contain chemicals, is also commercially available. Organic fertilizer comes from an organic source such as manure, blood meal, cottonseed meal, feather meal, crab meal, or others, as opposed to synthetic sources. Using slow-release organic granular fertilizer significantly decreases the chances of damaging lawns and plants. Organic fertilizers depend on the microbes in the soil to break them down into digestible bits for plants. Organic fertilizers tend to encourage soil microbes, earthworms, and other flora more than synthetic fertilizers do, because most organic fertilizers don’t add excess salts and acid to the soil.
Because granular fertilizers do not immediately affect plants, it may take a long time for positive results to show. Plants may not receive nutrients fast enough to help them recover from deficiencies. Granular fertilizers also need moisture and warm temperatures to act. The pH of soil may also influence their effectiveness.
Granular fertilizers deliver food to a plant slowly but have the advantage of longevity.
This method, which covers large areas well, is used to apply granular fertilizers to new beds before they are planted. The broadcast method can be done with a hand-rotary or drop spreader.
This technique, which provides nutrients to individual plants such as shrubs and perennials, is done by hand with granular fertilizers. Simply apply the fertilizer around the base of the plant, extending to the drip line.
Products to Use
Liquid fertilizers are liquid concentrates or water-soluble powders of synthetic chemicals that contain a mix of nitrogen, phosphorous, potassium and iron. They are easy to apply to plants. After following the directions to dilute the concentrate or create a liquid solution from powder mix, you can apply liquid fertilizer using spray bottles or sprinkler attachments.
Liquid fertilizer solutions act quickly to make nutrients available to plants. Some provide an immediate effect as cannabis leaves and roots absorb the mixture. They are great as a starter solution and for a quick boost during the growing season. The liquid nutrients generally last 1 to 2 weeks, so you need to reapply often. These products are usually easy to handle and do not take expensive equipment or intensive training to ensure correct application. They are, however, sometimes messier than granular types because of the mixing, and some contain a different dye that makes for easy identification but can stain.
Unfortunately, if growers do not carefully follow the directions for mixing or applying liquid fertilizer they can cause severe damage to the plants. Too much liquid fertilizer can burn the cannabis leaves, leaving discolored streaks, and damage plant foliage. The fertilizer solution can also leach deep into the soil, making it unavailable. Consequently, liquid fertilizer needs more frequent applications than other types of fertilizer. Liquid fertilizer may also contribute to water pollution if it seeps into storm drains.
Fish emulsion is a popular organic liquid concentrate fertilizer.
This method gives plants food while you water. Used with water-soluble fertilizers, follow the mixing instructions and water the soil at the plant’s base with a watering can or hose attachment. This is good for feeding container plants.
This approach is similar to base application, but the water is applied to the leaves instead of the soil. It is useful when cannabis plants need to quickly absorb trace elements, like iron.