Synthetic vs. Organic Fertilizer: What’s the Difference?

Synthetic vs. Organic Fertilizer: What’s the Difference?
The difference between organic and synthetic fertilizer is more nuanced than you might think.

Both come with misconceptions about their plant safety, their environmental impact, and which one is "better."

In this guide, we'll break down the main differences between synthetic vs. organic fertilizer so you can make the best decision for your yard.

Main Differences Between Synthetic vs. Organic Fertilizer 

What Is Organic Fertilizer?

Organic fertilizers are derived from plants or animal sources and are carbon-based. Examples include: 

• Blood Meal

• Bone Meal 

• Coffee Grounds

• Compost

• Composted Manure

• Corn Gluten Meal

• Fish Emulsion

• Kelp

Most organic fertilizers release nutrients slowly, providing the lawn with a consistent supply of nutrients for weeks or months. Fast-release options are available, though less common — blood meal and liquid fish emulsion are two examples.

What Is Synthetic Fertilizer?

Synthetic fertilizers, often referred to as inorganic fertilizers, are manufactured via industrial chemical processes that derive plant nutrients from mined mineral deposits, atmospheric gases, and fossil fuels. 

Most synthetic fertilizers release their nutrients quickly, however slow-release synthetic formulations are also available. 

Note: Fertilizers made of finely ground minerals — such as rock phosphate or greensand — are not organic in the chemistry sense, because they do not contain carbon. However, these naturally occurring substances are usually permitted in organic gardening programs. 

Organic Fertilizer’s Advantages and Disadvantages

Slow-release organic fertilizers are usually safer for the environment than fast-release synthetic fertilizers.

However, you may be surprised to learn that “organic” doesn’t automatically mean “environmentally safe.” 

Similar to their synthetic counterparts, fast-release organic fertilizers can leach a surplus of nutrients into groundwater or pollute local waterways. When improperly applied, even slow-release organic fertilizers can impact the environment.  

To ensure optimal environmental safety, always apply organic fertilizer responsibly and correctly. 

Advantages

• Most organic fertilizers release nutrients slowly over a long period, providing the lawn or garden with a steady supply of nutrients throughout the growing season. 

• Because nutrients are typically released slowly, there’s less risk of excess nutrients leaching into the groundwater or polluting local waterways via runoff. 

• Because organic fertilizers contain lower concentrations of nutrients, there’s less risk of overapplication or fertilizer burn. 

• Organic fertilizers typically contain a variety of micronutrients. 

• Organic fertilizers typically contain organic matter, which contributes to the soil’s health, ecosystem, and microbial diversity. 

• Organic fertilizers are often less energy-intensive to extract than synthetic fertilizers, and require minimal processing.

• The vast majority of organic fertilizers are derived from renewable resources. 

Disadvantages

• Excess nutrients from fast-release organic fertilizers can leach into groundwater and pollute local waterways. 

• Since most organic fertilizers release nutrients slowly, this option may not be ideal for plants or turfgrasses that need an immediate supply of nutrients. 

• Organic fertilizers contain a lower concentration of nutrients than synthetic fertilizers, which may not be ideal when the lawn or garden requires a high dosage. 

• Organic fertilizers are typically more expensive than synthetic fertilizers.

• Some organic fertilizers (particularly manure-based products) can produce significant methane and nitrous oxide. 

• Some organic fertilizers are high in salts, so the risk of fertilizer burn is not zero.  

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• Nutrient amounts in organic fertilizer vary, which may prove inconvenient when the soil needs a precise measurement of nutrients.

Synthetic Fertilizer’s Advantages and Disadvantages

Most synthetic fertilizers contain nutrients in forms that are immediately available to plants. 

While this rapid supply of nutrients can boost an ailing plant, the plant often can't absorb all the nutrients fast enough. As a result, the excess nutrients may leach into the groundwater or pollute local water systems. 

Fortunately, slow-release synthetic fertilizers are available for purchase, and they are much less prone to leaching and runoff than fast-release fertilizers. 

Advantages

• Slow-release synthetic fertilizers help close the leaching gap and are significantly safer for the environment than common fast-release synthetic fertilizers. 

• Slow-release synthetic fertilizers release nutrients over a long period of time, similar to most organic fertilizers.  

• Synthetic fertilizers contain a high concentration of nitrogen, phosphorus, and potassium, which are the three most important nutrients plants need. 

• Nutrient amounts in synthetic fertilizers are highly accurate and consistent, making them useful for precise applications. This can prove especially convenient when basing nutrient amounts on soil test results. 

• Synthetic fertilizers are typically more affordable than organic fertilizers. 

• Most synthetic fertilizers are fast-release and make nutrients immediately available to plants. 

Disadvantages

• Fast-release synthetic fertilizers contribute to leaching and polluted runoff. This is a less common issue with organic fertilizers, which are more often slow-release. 

• Because synthetic fertilizers contain higher nutrient amounts, they are more likely to cause fertilizer burn than organic fertilizers. 

• Synthetic fertilizers usually do not contain a wide range of micronutrients.

• Synthetic fertilizers do not contain organic matter, which is necessary for the soil’s health, ecosystem, and microbial diversity. However, some commercial fertilizer blends do contain a mixture of synthetic fertilizer and organic matter. 

• Synthetic fertilizers require more energy to extract and manufacture than organic fertilizers. 

• Synthetic fertilizers are derived from non-renewable resources, including minerals, natural gas, and petroleum.

Which Fertilizer To Choose: Organic Or Synthetic?

When choosing between organic and synthetic fertilizers, it comes down to your lawn's needs and how you plan to apply them.

If you need a high concentration of nutrients that you can accurately measure but also want to avoid leaching, choose a slow-release synthetic fertilizer. If you want a higher dose of organic matter and micronutrients, choose a slow-release organic fertilizer.

Whichever you choose, application rate and timing matter as much as fertilizer type. Excess fast-release nutrients — whether organic or synthetic — can leach into groundwater and pollute local waterways.

Leave Lawn Care to the Pros

Applying fertilizer safely is just one essential part of responsible lawn care. Mowing properly, aerating soil, and watering wisely also play a role in your lawn’s health and local environment.

The better you take care of your lawn, the less chemicals it needs to rely on, whether that’s synthetic fertilizers, insecticides, herbicides, or fungicides. 

To avoid falling behind on maintenance, consider hiring a local lawn care professional to mow, aerate, and maintain your turfgrass. GreenPal makes finding a trusted pro easy by connecting homeowners to lawn care pros in many cities across the country, including Greensboro, NC, Fort Worth, TX, and Stamford, CT.