Soft Secrets: Mixing Fertilizers

Always read the entire label, and follow the directions. To mix, dissolve the powder and the crystals into a little warm water, and make sure it is totally dissolved before adding the balance of the tepid water. This will ensure that the fertilizer and the water mix evenly. Liquid fertilizers can be mixed directly with water.

Containers have very little growing medium in which to hold the nutrients, and toxic salt buildup may become a problem. Follow dosage instructions to the letter. Adding too much fertilizer will not make the plants grow faster. It could change the chemical balance of the soil, supply too much of a nutrient, or lock in other nutrients making them unavailable to the plant.

Measuring – Always use an accurate measuring container.

Fertilizer Application

Some varieties can take high doses of nutrients, and other strains grow best with a minimum of supplemental fertilizer. See the chart below for recommendations on fertilizing a few varieties. Many fertilizer programs are augmented with different additives that expedite nutrient uptake.

Determine if the plants need to be fertilized: make a visual inspection, take an N-P-K soil test, or experiment on test plants. No matter which method is used, remember, plants in small containers use available nutrients quickly and need frequent fertilizing, while plants in large planters have more soil, supply more nutrients, and can go longer between fertilizing.

Pale green leaves signify this plant is low on nitrogen and needs to be fed with an all purpose fertilizer.

Visual Inspection – If the plants are growing well and have deep green, healthy leaves, they are probably getting all necessary nutrients. The moment growth slows or the leaves begin to turn pale green, it is time to fertilize. Do not confuse yellow leaves caused by a lack of light with yellow leaves caused by a nutrient deficiency.

Taking an N-P-K soil test will reveal exactly how much of each major nutrient is available to the plant. The test kits mix a soil sample with a chemical. After the soil settles, a color reading is taken from the liquid and matched to a color chart. The appropriate percent of fertilizer is then added. This method is exact but more trouble than it is worth.

Experimenting on two or three test plants is the best way to gain experience and develop horticultural skills. Clones are perfect for this type of experiment. Give the test plants some fertilizer, and see if they green up and grow faster. You should notice a change within 3 to 4 days. If it is good for one, it should be good for all.

Now, it has been determined that the plants need fertilizer. How much? The answer is simple. Mix the fertilizer as per the instructions and water as normal, or dilute the fertilizer and apply it more often. Many liquid fertilizers are diluted already. Consider using more concentrated fertilizers whenever possible. Remember, small plants use much less fertilizer than large ones. Fertilize early in the day, so plants have all day to absorb and process the fertilizer.

Here are the fertilizer schedules from two well-established fertilizer manufacturers.

It is difficult to explain how often to apply all fertilizers in a few sentences. We know that large plants use more nutrients than small plants. The more often the fertilizer is applied, the less concentrated it should be. Frequency of fertilization and dosage are two of the most widely disagreed upon subjects among growers. Indoor containerized marijuana can be pushed to incredible lengths. Some strains will absorb amazing amounts of fertilizer and grow well. Lots of growers add as much as one tablespoon per gallon of Peters™ (20-20-20) with each watering. This works best with growing mediums that drain readily and are easy to leach. Other growers use only rich, organic potting soil. No supplemental fertilizer is applied until a super bloom formula is needed for flowering.

Fertilizing plants in the ground is much easier than fertilizing containerized plants. In the soil outdoors, the roots can find many nutrients in the soil, and fertilization is not as critical. There are several ways to apply chemical fertilizer. You can top-dress a garden bed by applying the fertilizer evenly over the entire area. You can side-dress plants by applying the fertilizer around the bases of the plants. You can foliar-feed plants by spraying a liquid fertilizer solution on the foliage. The method you choose will depend upon the kind of fertilizer, the needs of the plants, and the convenience of a chosen method.

When using synthetic fertilizers, it is extremely important to read the label carefully, and follow the directions. The initials “WIN” and “WSN” that you may see on the label stand for water-insoluble nitrogen and water-soluble nitrogen. WIN dissolves readily, and it is considered a fast-release nitrogen source. WSN does not dissolve easily. It is often an organic form of nitrogen and is considered a slow-release nitrogen source.

Use a siphon applicator—found at most nurseries—to mix soluble fertilizers with water. The applicator is simply attached to the faucet with the siphon submerged in the concentrated fertilizer solution with the hose attached to the other end. Often, applicators are set at a ratio of 1 to15. This means that for every 1 unit of liquid concentrate fertilizer, 15 units of water will be mixed with it. Sufficient water flow is necessary for the suction to work properly. Misting nozzles restrict this flow. When the water is turned on, the fertilizer is siphoned into the system and flows out the hose. The fertilizer is generally applied with each watering, since a small percentage of fertilizer is metered in.

A garbage can with a garden-hose fitting attached at the bottom that is set 3–4 feet (90–120 cm) off the floor will act as a gravity-flow source for the fertilizer solution. The container is filled with water and fertilizer.

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