What is the Difference between Fertilizer Derived from Organic and Synthetic Sources?

This graphic shows the differences between organic and synthetic fertilizers and the benefits of using organic fertilizer.

Fertilizers come from many sources. Synthetically derived fertilizers are manufactured from minerals, gasses from the air and inorganic waste materials. Fertilizers derived from organic sources obtain their nutrients from natural sources such as microbes, organic waste, and other similar materials.

What is Synthetically Derived Fertilizer?

Synthetic fertilizers are best known for being fast-acting and for coming in a variety of forms such as liquid, pellet, granule, and spike. Synthetic fertilizers are water-soluble and can be taken up by plants almost immediately. While this provides a quick-hit of nutrients and rapid greening, the color won’t last as long as when organically derived fertilizers are used.  Consumers must reapply synthetic fertilizers regularly to keep the results from fading.

Synthetic fertilizers give plants a quick boost but do little to stimulate soil life, improve soil texture, or improve your soil's long-term fertility. They’re highly water soluble and can leach into waterways. The quick results of synthetic fertilizers can come at a cost; apply too much and it may burn your lawn and plants. 

What is Organically Derived Fertilizer? 

Fertilizers derived from organic sources provide benefits to both plants and soil and when used properly generally won’t burn or damage plants. Organically derived fertilizers stimulate beneficial the soil’s microorganisms and improve the structure of the soil. Soil microbes play a key role in converting organic fertilizers into soluble nutrients that can be absorbed by plants at a rate they can use. Organically derived fertilizers often provide the secondary and micronutrients plants need, usually absent in synthetic fertilizers.

Organically derived fertilizers typically have a lower NPK analysis (nitrogen, phosphorus, potassium) than synthetics fertilizers, but they feed plants for a much longer period of time. As a result, the impact of organic fertilizers on lawn and plants is usually more subtle. It may take a little longer to see results, but the reward is a lawn that stays greener longer.

Quality Organic (natural) Synthetic (chemical)
Purchasing Convenience
  • Depending on the type of organic fertilizer used, it can be more expensive than synthetic fertilizers.
  • Available bag sizes aren’t large or economical enough for homeowners.
  • Synthetic fertilizers are most commonly used, readily available, available in greater amounts, and generally, cost effective.
  • Controlled-release pellets are more expensive.
Ease of Application
  • Some organic fertilizers are in their “raw” form, not pellets, and may take extra effort to distribute over large areas.
  • Generally, no harm will result from over application or spills.
  • Use a fertilizer spreader according to manufacturer rates.
  • Accidental over application, including overlapping rows when fertilizing, can cause lawns to burn.
Nutrients
  • Natural-based fertilizer nutrients can fluctuate.
  • Micronutrients are typically present, providing some of the trace nutrients plants require.
  • Nutrient amounts are highly accurate.
  • Blends can be formulated for specific needs.
  • High nutrient concentrations may build-up in the soil, which may lead to leaching and run-off.
  • Generally, don’t contain necessary micronutrients.
  • If it contains water-soluble iron, it can stain concrete.
Rate of Nutrient Release
  • Nutrients are released at a rate plants can use, greatly reducing the chance of leaching or run-off.
  • Microbes in the soil break down the organic material releasing the nutrients.
  • Requires fewer applications, which means less work over time.
  • Controlled growth that doesn’t over-stimulate plants, promotes stronger root growth for better disease and insect resistance.
  • Reliant on soil temperature: cooler soil = slower release rate, which corresponds to the rate plants can take up nutrients.
  • Poor quality soils depleted of beneficial microbes may delay results.
  • Long lasting.
  • Synthetic fertilizers give lawns and gardens a quick, but short-lived, burst of nutrients, which can cause rapid growth at the expense of developing a strong root system.
  • May see results in 1–2 weeks.
  • More mowing will be required due to rapid growth.
  • Water soluble in most forms.
  • Because nutrients are released quickly more applications will be required.
  • Many forms available: pellets, granules, liquid, tablets, spikes, and controlled-release.
  • Short-term solution to a long-term need.
Impact on Soil
  • Promotes a healthy soil ecosystem.
  • Provides organic material that decomposes, releases nutrients plants can use and feeds vital microorganisms, all important for rich, fertile soil.
  • Improves soil texture, which increases water retention, particularly important in drought conditions.
  • Synthetic fertilizers contribute very little to the ecosystem or structure of the soil.
  • May actually decrease soil fertility due to chemical nitrogen stimulating excessive microorganism growth, which, over time, depletes organic matter in the soil.
Plant Safety
  • In most cases, won’t burn plant leaves or roots.
  • Manure should be composted for greatest safety.
  • Incorrect or over application may burn plants due to high concentrations of chemical nutrients, which are salts.
  • Can cause excess top growth and stress roots.
Environmental Safety
  • Minimal, if any, run-off or leaching.
  • Since water releases nutrients, a significant amount of nutrients can be lost from run-off and leaching, sometimes up to one-third.

Milorganite has some of the best qualities of both types of fertilizer. It’s a convenient, pelletized fertilizer derived from organic materials, which help keep the soil fertile and conditioned to retain water. Its nutrient analysis (N-P-K) is consistent and it contains non-staining iron. It’s derived from dead microbes, so it won’t burn lawns or plants. It’s also cost effective, easy to apply, and readily available in convenient, large bags for homeowners.

Melinda Myers, horticulture expert, reviews the differences between organic and synthetic fertilizer and how to select the right fertilizer for your lawn and garden.

Horticulture expert Melinda Myers explains how to select the proper fertilizer for your lawn and garden.