Organic Fertilizer vs. Synthetic Fertilizer

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There are many different fertilizer products on the market for home gardeners today. How do you know the right choice for your plants? In this article, I will break down the differences between synthetic and organic fertilizers so you can choose the best fertilizer for your needs.

Selection of fertilizers

While there are significant differences between organic and synthetic fertilizers, it’s important to note that your plants will not know the difference between the two. Either way, you are feeding your plants and the nutrients are the same.

Tip: It is worth getting a professional soil test to determine exactly what essential nutrients are needed in your garden soil.

Organic Fertilizer vs. Synthetic Fertilizer – At A Glance

Organic fertilizerSynthetic fertilizer
Minimally processed or not processed at allManufactured and refined from natural ingredients
Nutrients are released slowly with decompositionNutrients are immediately available to plants
Less precise measurementsPrecise and consistent measurements
Difficult to over fertilizeOver applying is more likely
Helps build soil with organic matterDoes not help build soil

What Is Fertilizer?

Fertilizers supplement soil when the soil’s nutrient supply is inadequate for strong plant growth. Synthetic fertilizers, organic, or a combination of both can be used to support the growth of plants.

When looking at the label of a fertilizer bag, the amount of the three primary nutrients is expressed as a percent of the total fertilizer weight. This is known as the “NPK Ratio.” Nitrogren (N) is listed first, followed by phosphorus (P) and potassium (K). This is explained in more detail below.

How Are Synthetic and Organic Fertilizers Made?

Fertilizer contents

Synthetic fertilizers are manufactured and refined from natural ingredients. The manufacturing process is often very energy intensive. Ammonium sulfate and urea are both examples of synthetic fertilizer.

Organic fertilizers are minimally processed or not processed at all. They are derived from natural and organic sources such as plants, animals, or minerals. Often, organic fertilizers are made of materials that would otherwise go to waste. A few ingredients you may see in your organic fertilizer are bone meal, greensand, seaweed, and alfalfa. 

How do these fertilizers feed your plants?

Synthetic fertilizers dissolve very quickly in water, making them immediately available to plants. This quick release of nutrients impacts plants much quicker than organic fertilizer and is useful if you need to correct a nutrient deficiency.

The measurements are also more precise and consistent. When using a synthetic fertilizer, you know exactly how much of each nutrient is being applied. However, it is very easy to over apply synthetic fertilizers and give your plants too much nutrients.

There is also an environmental impact when synthetic fertilizers are applied in excess. Excess nutrients that are not absorbed by your plants can run off into nearby water bodies and leach into groundwater.

Organic fertilizers are released slowly as organic matter decomposes over time. This supplies a more steady supply of nutrients over a longer period of time, while also improving the structure of your soil with organic matter. Nutrient levels are less precise and predictable, but over-fertilization is less likely with an organic fertilizer.

Understanding Fertilizer Ratios

Tiger bloom fertilizer

When purchasing fertilizer, there will be a ratio on the packaging indicating the amount of nutrients. With all of the numbers and percentages, this can be confusing to understand at first. These ratios are expressed as “N-P-K”, representing nitrogen, phosphorus and potassium.

We won’t go into too much detail with these nutrient ratios. However, it is important to understand that these are the three macronutrients necessary for plant growth and are required for a complete fertilizer.

Balanced fertilizer: A balanced fertilizer contains equal (or close to equal) amounts of each nutrient. For example, a 10-10-10 would be a balanced fertilizer. These are good general purpose/versatile options.

The role of each nutrient is also important to consider.

  • Nitrogen: Promotes leafy growth and branching.
  • Phosphorus: Helps form healthy plant roots, flowers and fruit production.
  • Potassium: Helps plants withstand stresses like drought and disease.

Different types of fertilizers

organic fertilizer

Fertilizers come in many different forms. Typically they are either synthetic or organic, liquid or granular, and slow-release or fast-release.

  • Synthetic Liquid – Water soluble nutrients that are used for quick feeding of nutrients that are available right away. Some foliar sprays are also in this category.
  • Synthetic Granular – Offers a balance of NPK nutrients. Sometimes seen in specialty blends.
  • Synthetic Slow-Release – Some synthetic fertilizers, like Osmocote, can be designed as “slow-release” to release their nutrients over a longer period of time. These slow-release formulas often come coated or in the form of large pellets, mimicking the breakdown of organic materials.
  • Organic Liquid – These fertilizers feed more quickly than organic fertilizer made of organic solids, like compost. They undergo processing which results in a liquid form that is more accessible to plants. Examples would be fish emulsion and seaweed extracts.
  • Organic Granular/Slow Release – Granular fertilizers are powdered or granular and applied to the soil. Examples would be blood meal, bone meal, alfalfa meal, and greensand. Some organic fertilizers release their nitrogen more quickly. Blood meal, feather meal, and fish meal are all excellent sources of nitrogen.

How to use fertilizers properly

Bag of bone meal

Regardless what type of fertilizer you use, proper usage is important. You want to supply nutrients to meet the needs of your plants, but you do not want excess nutrients in the soil. These excess nutrients can cause environmental issues as they leach or run off into water.

Always follow the instructions on the package of the fertilizer you are using. We also recommend performing a soil test to determine exactly what nutrients your soil may need.

Apply fertilizer when your plants need them, during their active and rapid growth. For example, you will fertilize your lettuce sooner than you would your melons.

Which Is Best?

Both synthetic and organic fertilizers have their roles when it comes to gardening. If you are in need of quick nutrient delivery to correct a deficiency, synthetic fertilizers will be the better option. Container plants, houseplants, and fast growing annuals also benefit from synthetic fertilizers.

Organic fertilizers will contribute to the health of your soil with long-term use, but will require more time and larger amounts to provide the same level of nutrients.

The choice you make depends on your personal needs, as well as the needs of your plants during the growing season. We recommend using a combination of both as you see fit. For the best results from your garden, use your fertilizer responsibility and work on building your soil over the long-term.

– Crystalyn

Always looking for new ways to get creative in the garden, Crystalyn enjoys getting her hands dirty with vegetables, flowers, and tropical plants. In the off-season, you’ll find her moving the hobby indoors with her vast houseplant collection.

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