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? If you’re not sure about any of these questions, then you’re in the right place.
Choosing a fertilizer can be a confusing. Selecting the right type of fertilizer requires knowing the exact cause of plant illness you want to fix or how you want to help your plants grow. You have two options: liquid fertilizers or solid granular fertilizers. Determining the pros and cons of each type can help you choose the right method for creating a healthy environment for your plants.
Granular fertilizers are solid granules that need a while to dissolve or decompose before 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 temperature and rainfall.
- 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.
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.
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.
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. As with liquid fertilizer, inappropriate application of granular fertilizer will leave telltale streaks and spots of burned grass on lawns.
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 lawns or 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. For vegetables, place the fertilizer in a strip parallel to the planting row.
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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 lawns and 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 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 blue or green dye that makes for easy identification but can stain.
Unfortunately, if gardeners do not carefully follow the directions for mixing or applying liquid fertilizer they can cause severe damage to plants and lawns. Too much liquid fertilizer can burn grass, leaving discolored streaks on the lawn, and damage plant foliage. The 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 and vegetables.
This approach is similar to base application, but the water is applied to the leaves instead of the soil. It is useful when plants need to quickly absorb trace elements, like iron.
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Last Minute Tips
By improving the soil with plenty of compost and organic matter, less fertilizer is needed. However, vegetables need plenty of phosphorous and potassium, so the fertilizer should contain plenty of each. For the long lived vegetables, such as tomatoes, using an organic fertilizer or a coated high-tech product that releases nutrients slowly over a period of time is recommended. Supplementing with a liquid food also improves plant health and growth. And always remember to enjoy your growing experience!