I’ve been using granular fertilizer for my container garden. I heard that liquid fertilizer can be fast-action and was curious if I could dissolve granular fertilizer in water and use that instead.
You can dissolve granular fertilizer in water though it will take about 24 hours or more to completely dissolve. You can use the solution as a liquid fertilizer for quickly providing essential nutrients to your container plants.
By making your own liquid fertilizer from granular fertilizer, you are getting the best of both worlds. You can have the cost-saving and long shelf-life of dry fertilizer, and create your own liquid fertilizer whenever you need it.
The process of creating liquid fertilizer from granular fertilizer is simple. I’ve written the details of how you can do the same for your plants as well.
How to Dissolve Granular Fertilizer in Water
Follow the steps laid out below to correctly dissolve granular fertilizer in water. Be sure to dilute the resulting liquid to avoid damaging your plants.
The only equipment needed is a bucket or other container, a measuring cup, and something to stir the mixture with.
Start by figuring out how many gallons of liquid fertilizer you need, so you can calculate how much granular fertilizer to dissolve. Using one cup of granular fertilizer will give you 8-16 gallons of diluted fertilizer for watering, or 1 gallon for foliar feeding.
Using 1 cup of granular fertilizer per gallon of water, soak for 24-48 hours. Stir the mixture occasionally to help the granules dissolve more quickly.
After soaking, there will still be some solids left in the bottom of your container that cannot dissolve. Strain these out and keep them to use later. They can be sprinkled in flower beds or used for plants that don’t need as much fertilization.
The resulting liquid is ready to use for foliar feeding at full strength, or it can be diluted 1 to 2 cups per gallon for watering.
Note: you may see water-soluble fertilizer when you are shopping for garden supplies. This product is meant to be dissolved in water and used immediately, so it does not need the same soaking time as granulated fertilizer. Follow instructions on the packaging if you have this kind of fertilizer.
Although it takes a bit more time than using liquid fertilizer straight from the bottle, there are significant advantages to dissolving granular fertilizer in water.
Granular Fertilizer vs. Liquid Fertilizer
Ultimately, most fertilizers contain identical ingredients: nitrogen, phosphorus, and potassium. These are the three macronutrients used by plants, and they can be found in various configurations depending on what kind of plant you are growing and what result you want from the plant. For more details about fertilizer formulations, you may find this article useful.
Knowing that both liquid and granular fertilizers have the same components, the only difference is in how those components are conveyed to the plants.
Granular fertilizer is meant to release slowly into the soil, so the granules are made with a slow-dissolving coating. Liquid fertilizers already have the components dissolved, so they are ready for the plants to use immediately. (Source: Bonnie’s Plants)
For the purposes of this article, we are assuming a typical all-purpose 10-10-10 fertilizer that has equal parts of each component. If your granular fertilizer is stronger or has a higher percentage of any one macronutrient, you may want to experiment with diluting further to avoid damaging your plants.
Benefits of Granular Fertilizer
Granular fertilizer is incorporated into the soil or sprinkled around the base of the plant. For container gardening, it is usually best to work a granular fertilizer into the soil when you plant it in the container. The advantages of granular fertilizer are that it lasts for a long time, is easier to store, and is cheaper than liquid fertilizer.
Depending on the type, granular fertilizer can last from 1-9 months. Since the granules break down slowly, they release nutrients over time. The packaging should indicate how long it is intended to feed your plants, but note that the fertilizer will not last nearly as long if you dissolve it in water before using it.
Granular fertilizer, overall, has a long shelf-life. Its mineral components have no specific expiration date, but the fertilizer should be stored in a cool, dry location for the best results. If it absorbs too much humidity, it tends to clump, but still does not lose its potency.
Drawbacks of Granular Fertilizer
One disadvantage of granular fertilizer is that the application may not be as even as with liquid fertilizers. That is because each granule is likely to have more or less of certain nutrients. Especially in container gardening, it can be challenging to make sure the right balance of nutrients is available to each plant.
Granular fertilizer also limits the plant’s access to immobile nutrients such as phosphorus, even though it is a component in the fertilizer. This occurs because the plant can only absorb immobile nutrients if they are already dissolved in water.
A final disadvantage of granular fertilizer is that it can be easy to use too much, which can cause leaf burn (aka fertilizer burn) due to the high salt content. Estimating how much granular fertilizer to use is more difficult than with liquid fertilizer.
Benefits of Liquid Fertilizer
Liquid fertilizer, on the other hand, avoids all of the disadvantages listed above. By using your dry fertilizer to make liquid fertilizer, you can optimize the strengths of each type.
First, liquid fertilizer is easy to apply evenly. After diluting, liquid fertilizer will be delivered in equal parts since the components are distributed equally in the water. You can use liquid fertilizer in the soil when watering, or for foliar feeding.
Plants can use the nutrients immediately when provided in a liquid form. Unlike granular fertilizer, there is no need to wait for it to break down slowly. If your plants need an immediate boost, liquid fertilizer is definitely the preferred option.
Liquid fertilizer provides better nutrition to plants because they can access immobile nutrients readily. The nutrients are already dissolved in the liquid, which means they can be accessed directly by the plant when the liquid comes in contact with roots or leaves.
Drawbacks of Liquid Fertilizer
Liquid fertilizer is heavier and more difficult to store than granular fertilizer. It should not be allowed to freeze, since the components can separate when they thaw. There’s also a danger that it will expand enough to break the storage container, leading to loss of fertilizer.
Liquid fertilizer is more expensive. The initial purchase price of liquid fertilizer is higher than granular, and you will also need to apply it more often. If you have many plants to feed, prices can add up quickly.