Do you want to choose a fertilizer for your plants but their variety overwhelms you? In this article, we will talk about the different fertilizer types and classify them based on various criteria.
Fertilizers are an essential part of a plant’s life. Whether we’re talking about garden plants, container plants, or crop plants, they all need fertilizers to flourish, produce flowers or fruits, and deliver the best yield.
In addition to water, oxygen, and light, plants need various nutrients to develop harmoniously.
Naturally, different soil types contain more or less of the nutrients necessary for plant growth. However, they are an exhaustible source if not substituted in some way.
In nature, most nutrients in the soil are replenished through the decomposition of dead plants and animals.
In environments where plants are grown repeatedly for consumption, cultivated industrially, or in the case of plants grown in containers, the nutrients in the soil can deplete and various deficiencies may appear, leading to the occurrence of various diseases and poor yields.
This is where fertilizers come into play. They not only restock the nutrients in the soil but also allow the plants to grow even in soil types that are naturally poor in nutrients.
There is a wide variety of fertilizers on the market and choosing the best fertilizer for each situation can be a daunting task, especially if you do not understand exactly the differences between the different types of fertilizers and when they should be applied.
When the wrong fertilizer is used, or at an incorrect rate, it can do more harm than good to plants. Overfertilization is a fairly common cause of plant diseases, thus, it’s important to apply the appropriate fertilizer at the right time.
If you want to learn more about the role of fertilizers, we recommend that you also read this article.
Further, we will talk about the different fertilizer types and how to choose the most suitable one for your plants.
Fertilizers can be classified according to various criteria. These include things like their nature, form, time of action, etc.
- Fertilizers By Origin
- Fertilizers By Form
- Fertilizers By Release Rate
- Fertilizers By Purpose
- Fertilizers By Environment
- Fertilizers For A Particular Deficiency
- Fertilizers With Added Components
- Final Word
Fertilizers By Origin
One of the classifications of fertilizers is according to their origin.
According to this categorization, fertilizers can be either natural or synthetic (which are also known as artificial or chemical).
Natural fertilizers are produced from natural components that often include compost, animal waste, manure, guano, or biosolids (organic matter recycled from sewage).
Although their price is higher, these fertilizers are environmentally friendly and eliminate most of the risks and negative effects associated with chemical fertilizers.
However, they are not as effective as synthetic fertilizers, because their chemical composition is not artificially controlled and they do not supply immediate results as the nutrients take time to be released. They are regarded as slow-release fertilizers (SRF).
Natural fertilizers incorporate essential macronutrients like nitrogen, phosphorus, and potassium, as well as a variety of micronutrients. Yet, they come in lower concentrations than those found in synthetic fertilizers.
These organic fertilizers are often deemed as soil amendments rather than fertilizers because they are used mainly to improve soil quality instead of feeding the plants directly. They are oftentimes used concurrently with synthetic fertilizers to complement each other.
Chemical or synthetic fertilizers are industrially and artificially produced from various compounds.
Just like natural fertilizers, these are utilized to control the shortage of nitrogen (N), phosphorus (P), potassium (K), and other essential nutrients in the soil required for plant growth.
These types of fertilizers are widely used to achieve maximum productivity in traditional agricultural systems as they are cheaper than natural fertilizers and provide quicker results.
Even if they have numerous advantages, the long-term usage of chemical fertilizers can carry numerous negative effects on the environment and on the health of people and animals.
Synthetic fertilizers are available in many forms and with different concentrations of essential macronutrients (N-P-K ratio).
Fertilizers By Form
Another classification of fertilizers is based on the state in which they are available.
The form in which the fertilizer is delivered may have both advantages and disadvantages depending on one case to another.
They can be further classified into dry fertilizers and liquid fertilizers.
Some dry fertilizers, such as powders, sometimes must be dissolved in water before use, hence, becoming liquid fertilizers.
Dry fertilizers are the most habituated type of fertilizers in large-scale agriculture. These can have benefits like a slower release of nutrients and can be stored more efficiently and for more time compared to many liquid fertilizers.
Dry fertilizers are also available in a variety of forms.
Granular fertilizers generally come in the form of pellets.
An advantage of granular fertilizers is that they may provide nutrients to plants for a longer period than liquid fertilizers. Unlike liquid fertilizers that are quickly absorbed by the soil, granular fertilizers are dispersed gradually.
This may also be considered a disadvantage if you are looking for a fertilizer with immediate action. For that, typically liquid fertilizers are better.
A drawback of this type of fertilizer is connected to the uniformity of its application. If applied unevenly, some plants may receive more fertilizer and others less.
On large surfaces, it is usually applied with the help of a spreader. This ensures a more efficient and quicker application.
Granular fertilizer is a popular option for large agricultural areas or lawns, but it can also be used in gardens, flowerbeds, or orchards.
Fertilizer spikes are solid bars made of a mix of essential nutrients for plant development.
These rods are inserted into the ground close to the plant and supply nutrients to it for an extended time.
This fertilizer type is often used for potted plants, trees, and even garden plants.
It is an effective fertilizer because the nutrients are released close to the roots of the plant and for an extended period.
Powder fertilizers are usually quick-release, water-soluble fertilizers. Depending on one product to another, these can be either applied directly as powders or have to be mixed with water.
This type of fertilizer is usually one of the most cost-effective.
Liquid fertilizers are fertilizers applied in liquid form.
They usually have fast action, providing plants with the necessary nutrients in a short time after fertilization.
Liquid fertilizers either come directly in liquid form or as a powder that requires mixing with water in the quantities recommended by the manufacturer.
According to the method of application, they can be classified into two types, ground-applied or foliar.
Normally, the way in which a liquid fertilizer can be applied is specified on the packaging of each product. Some can be applied both on the soil’s surface and foliar.
One of the ways of applying liquid fertilizers is on the surface of the soil. Like most fertilization methods, this one also comes with advantages and disadvantages.
An advantage is that fertilizer can quickly reach the roots of the plants and provide the necessary nutrients.
A drawback is that you have to be careful when applying it. It can be easily washed away by the rain and extend to other areas where you might not want it.
High temperatures also can cause the liquid to evaporate before the nutrients are absorbed by plants.
Foliar fertilization is the application of liquid fertilizer via spraying on the plant’s foliage. The plant will thereafter absorb nutrients through its leaves and stems.
This type of fertilization can provide nutrients faster to a plant than ground fertilization. However, there is also the risk of quickly killing the plants if using the wrong doses of fertilizer.
This approach is also very efficient concerning nutrient losses and you can even combine the fertilizers with fungicides or insecticides, without doing the work separately several times.
Just as in the case of application at ground level, you must be very careful when applying this fertilizer on the foliage because high temperatures or precipitation can compromise the action.
Another disadvantage of foliar fertilizers is that they do not have long-lasting action.
Fertilizers By Release Rate
Another criterion by which we can classify fertilizers is based on how quickly the nutrients are released.
The form in which a fertilizer comes does not necessarily indicate whether it is a slow or quick-release fertilizer. There are even liquid fertilizers that have a slow-release action. Therefore, always read the label of each product.
Slow-release fertilizers are utilized to provide food to plants for an extended period of time (usually several months).
The nutrients initially come in a form that makes them unavailable for immediate uptake by the plant and are released gradually in small amounts.
Most common synthetic slow-release fertilizers come in the shape of pellets or spikes. These are slowly dissolved by moisture, temperature, and microbial organisms and released into the soil so that plants can make use of them whenever needed.
Quick-release fertilizers make the nutrients quickly available to the plants. While this is a good thing in general, it can also lead to overfertilization if applied incorrectly.
Another disadvantage of quick-release fertilizers is that they don’t deliver the nutrients for a prolonged period. Hence, you’ll need to fertilize the plants again after a short period.
These fertilizers are a good choice for new turfs, plants that have known nutrient deficiencies, or plants that need an immediate nutrient boost.
Controlled-release fertilizers (CRF) are not as common as slow or quick-release fertilizers. They are also known as delayed-release fertilizers, controlled-availability fertilizers, metered-release fertilizers, or coated fertilizers.
Similar to slow-release fertilizers, they have a delayed rate of freeing nutrients to plants after application. However, this pace is more stable in CRF fertilizers and not influenced as much by the microbial activity in the soil, humidity, and temperatures. Thus, offering more predictable and reliable results.
Controlled-release fertilizers typically come as granules coated or encapsulated with organic or inorganic materials that help in controlling the rate, pattern, and duration of the nutrient release.
Fertilizers By Purpose
There are both fertilizers that are recommended for use on a wide variety of plants, but also others intended for use only for particular species or in a specific developmental stage of a plant.
All-purpose fertilizers are intended to be utilized in order to deliver essential nutrients to a wide range of plants.
They usually come with a balanced rate of N-P-K or values suitable for the growth of many plant types, without the risk of burning them.
Although these products are labeled as “all-purpose,” it is recommended that you read the manufacturer’s instructions before using such a product and make sure it’s safe to use on your particular plants.
For specific plants or purpose
As opposed to all-purpose fertilizers, there are the ones designed for particular plant species or a specific growth stage, like for encouraging fruit production or blooming.
These types of fertilizers contain a rate of essential macronutrients (N-P-K) optimized especially for a plant type or for a certain period when it requires a larger amount of a certain nutrient.
For instance, some lawn fertilizers may have a higher concentration of nitrogen (N) to give the turf a greener color (eg. 30-0-4).
Fertilizers By Environment
Fertilizers can also be classified according to the environment in which they will be used.
We have both fertilizers intended for plants grown outside, but also others for potted plants grown indoors.
Fertilizers intended for outdoor use have certain characteristics that allow them to withstand various atmospheric conditions, such as precipitation, or high or low temperatures, without losing their properties.
These types of fertilizers can come in various forms. This is not the most substantial thing, but it is important to be specified on the packaging of each product that it can be utilized for outdoor plants.
Outdoor plants may also receive nutrients from natural sources like decaying parts of nearby plants, helped by mycorrhizal fungi, earthworms, etc. Thus, the concentration of nutrients in outdoor and indoor fertilizers may differ.
Fertilizers for indoor plants are created to be used in different conditions compared to plants grown outside.
The potting mixes for indoor plants are many times soilless mediums. Other elements like peat moss, coconut coir, or other alternatives are typically preferred instead of soil because of their properties that prevent compaction and provide better water drainage and airflow.
However, these environments are often poor in essential nutrients required for plant growth or they are almost completely absent. That’s why fertilizer is usually added to these mixes.
The initial fertilizer that comes included in the growing medium can wear off quickly after repeated waterings, especially since a part of the water frequently leaks through the drainage holes at the bottom of the pot, carrying a part of the nutrients in the soil with it.
Therefore, the fertilizers designed for indoor plants may contain macro and micronutrients in higher quantities compared to those for garden plants. The frequency of their application may also vary.
Fertilizers For A Particular Deficiency
Besides nitrogen (N), phosphorus (P), and potassium (K), which are considered the main macronutrients required for healthy plant growth, there are also other macronutrients and micronutrients needed for harmonious plant development, like calcium (Ca), magnesium (Mg), sulfur (S), etc.
Not all fertilizers contain all these additional nutrients or some of them in very small quantities.
If your tomato plants, for instance, have a calcium deficiency, chances are they will produce fruits affected by a condition called blossom-end rot.
As you are able to identify the leading cause of this disease, which in this case is a calcium deficiency, you will need to add more calcium to the soil.
Therefore, you don’t want to buy an all-purpose fertilizer or make your buying decision based on its N-P-K ratio. Instead, you will want to look for a fertilizer that includes a high concentration of calcium.
In conclusion, sometimes you will want to choose a fertilizer designed to treat a specific nutrient deficiency.
Fertilizers With Added Components
In addition to nutrients and other substances necessary for plant growth, some fertilizers may also contain fungicides, insecticides, or herbicides.
A lawn fertilizer, for instance, can be a mix of elements. Firstly, a fertilizer to help the grass thrive, and at the same time can contain a fungicide to protect it against various fungal diseases, an insecticide to control pests, and also a herbicide designed to kill dandelions or other species of weeds that commonly occur in turfs. All these benefits with just one application of the product.
Therefore, based on your needs, you may wish to choose a product that is actually a mix of components necessary for plant care instead of using a simple fertilizer.
This may be both more cost-effective and remove the extra work needed to apply all of these products separately.
Choosing the right fertilizer for your plants may be an overwhelming task due to the variety of products available.
There is a multitude of different fertilizer types, with different nutrients and in varying concentrations. So, it’s important to have a basic knowledge of how fertilizers work and which one is the most suitable for your plant types.
We hope that the information presented in this article will help you understand the different classifications of fertilizers based on multiple points of reference. Thus, making your decision of choosing a fertilizer easier and better informed.
As there are so many types of fertilizers with different purposes and nutrient concentrations, always read the usage instructions on the label of each product.