Garden & Greenhouse


The Good and Not so Good of Synthetic and Organic Plant Food

Posted March 3rd, 2015 by Kyle L. Ladenburger in ,

Over the last couple of decades the divide between the organic growers and the synthetic growers has become the schism of our industry. Debates over the topic often digress into nearly bitter exchanges as growers usually choose one side to belong to and, with willful ignorance, simply write off the opposing side as uninformed or under educated. The inherent complexity of the situation is usually overlooked, with each of the two camps usually claiming unequivocally that their method, be it organic or synthetic, is not only the best but also the most righteous.

Wrapped up tightly within a certain belief, many growers are unable to take an open minded look at the opposing sides view point. But, as I have found, growers that can remove all bias from their minds and take a clear headed look at the debate will be quick to notice that the issue is not as completely black and white as they once thought.

The following is an unbiased breakdown of some of the more notable pros and cons attributed to both sides.

The Good about Organic Plant Food

Contain no Soluble Salts

By definition, true organic plant foods contain natural sources of the elemental nutrients essential to plant growth. The nutrients exist as part of an organic matrix of sorts and are attached to a Carbon (C) molecule by a strong, stable bond. Elements in this form are free of soluble salts and their use will not result in salt build within the rooting medium. The result is a root zone that will not require additional flushing to get rid of said build up.

Improve the Biology of the Rooting Medium

Organic plant foods require microbial decomposition before they will release the elemental nutrients held within. This means that the organic matter will serve directly as a food source for actively growing microorganisms like beneficial bacteria and fungi. The more biologically active the rooting medium is, in both container and soil gardening, the faster the organic materials will be broken down releasing the nutrients that are readily available for uptake via the roots.

Most are Sustainably Sourced

This is especially true with products that receive an organic certification from a reputable certifying agency. These products are looked at with heavy scrutiny to ensure that they are both safe and sustainably sourced. For example, the manufactures of an OMRI certified Earthworm Casting product must provide elicit proof that the food source the worms consume to create the castings is also organically sourced. Other organic plant food products, including bone meal, blood meal and poultry manure, are the product of a completely different industry such as slaughterhouses and egg farms.

Safe to Use 

A major marketing point for organics is the fact that organic plant foods are safe for people, plants and pets. When it comes to the vast majority of these products the user doesn’t need to take any safety precautions when applying or handling. However, some products are rather dusty which can be irritating. I would advise that when you are applying large amounts, to wear a dust mask just in case.

The Not So Good About Organic Plant Food

Nutrients are Not Immediately Available

As was stated earlier, the elemental plant nutrients contained within organic fertilizers are bonded tightly to a Carbon molecule. Microorganisms must first degrade that bond before the nutrients are released in a form that is readily available to plants roots. This can leave the grower with an uncertainty as to how much of a certain nutrient will be available and exactly when it will be present. Most growers are not fans of uncertainty.

Not a Reliable Source of Nitrogen (N)

Finding a sufficient source of Nitrogen is one of the main struggles an organic grower will encounter. Organic matter does not contain a sufficient supply of Nitrogen to satisfy the needs of crops like corn, tomatoes and cucumbers. This problem is compounded by the slow release nature of organic nutrients. Many soil growers utilize the help of certain Nitrogen fixing cover crops to try and raise the level of Nitrogen in the soil.

Usually Contain Unknown “Accompanying” Elements

Simply stated, organic plant foods come from living organisms, be it plant or animal. While these organisms were alive and growing they required the same elements that the plants in a garden require. Hence the reason these products are used as fertilizers. However, the overall array of nutrients is often horrifically understated on the product labels. A couple years back I participated in a small study where we sampled 6 different earthworm casting products and had them analyzed for their elemental nutrient content. To our surprise, all of the products contained not only micro nutrients but also secondary and primary as well. The vast majority of these elements were not present on the product label. Imagine a grower that is using a casting with an NPK value of 1-0-0, without the slightest clue that the product actually contains a wide variety of “accompanying” elements. Without this information it is easy for the grower to unknowingly and accidentally create a severe imbalance in the rooting zone. If a grower is planning on using an organic input product in a commercial operation I would strongly recommend getting it tested by a lab to see exactly what it contains.

Risky for Traditional Hydroponics

Though organics can be used in hydroponics it should be down wisely and with caution. The first problem is the fact that the organic material needs to be further broken down.  In hydroponics the nutrients are delivered directly to the roots in a readily available form designed for immediate uptake by the plant. The question then arises, where and how will the organic material breakdown and be converted to available plant nutrients? This may result in a complete waste of the organic fertilizer. The second possibly problematic aspect of organics in hydroponics is the biological nature of organics. The introduction of a biologically active component into a more or less sterilized system can easily result in the attraction of many different pests and diseases.

The Good about Synthetic Plant Food

Nutrients are Immediately Available

This is one of the main reasons leading to the overall popularity of synthetic fertilizers. Elements in these forms exist as readily absorbed ions, leaving little doubt as to when and how much of the nutrients will be available to the plant. Synthetics can also be manufactured to behave as a slow release nutrient source if desired.

Complete Batch Consistency

Synthetic fertilizers are manufactured in factories with carefully formulated batches developed to create specific concentrations of the desired elements. Most manufacturers use due diligence and lab testing to ensure that what is in the final, packaged product is the same every time.

Huge Product Variety from General Use to Specific Supplements

Manufactures of synthetic fertilizers have the ability to design a mix to fit any type of request. Products can range from complete general use formulations to more element specific ones that can address a single elemental nutrient need. Growers that use these products have the ability to apply a specific nutrient at a desired rate to improve plant growth and avoid nutrient deficiencies.

Easy Application

Many synthetic/inorganic fertilizers are in liquid form making the mixing and applying of the products relatively easy. Products are often highly concentrated allowing the grower to use smaller amounts over larger areas. Dry, granular versions of these products can be easily distributed in a garden by hand (wear gloves!) or with a broadcast spreader.

The Not so Good About Synthetic Plant Food

Potential Salt Accumulation and Build Up

Unlike their organic counterparts, the nutrients in synthetic fertilizers are part of a soluble salt compound. When they are improperly or overly used these salts can accumulate within the rooting medium, leading to unwanted problems. The users of synthetics often find it imperative to flush or leach the rooting medium to get rid of the excess salt. This is more easily done in container growing compared to soil growing where leaching is much harder to do.

Potential for Creating Environmentally Damaging Runoff

When certain synthetic forms of elemental nutrients enter into public water ways or ground water they have the potential to cause severe ecological problems. Nitrate and Phosphate runoff can result in water that is unable to sustain a normal ecosystem and can be potentially harmful when consumed by animals and humans.

Limited Resources

For lack of a better word, organic fertilizers are grown. Where, in contrast, synthetics are most often mined from within the earth and then manufactured. This inherently makes them unsustainable to a certain extent. As their use and popularity spreads, the availability will inevitably decline.

Potentially Harmful Products

As the name implies, synthetic fertilizers are manufactured in a number of ways. Many of these processes incorporate the use of harsh and hazardous chemicals to help create and maintain the stability of the formula. This, in turn, results in products that are not only effective but potentially harmful if used in an improper or unsafe fashion. Synthetic fertilizers should always be handled and mixed carefully, with proper safety gear, and they should never be left where a young child can easily access it. Some products can irritate the skin, release fumes and, when consumed, even lead to real medical emergencies.

As the debate between organic and synthetic fertilizers rages on, it is important to remember that the issue is not nearly as black and white as so many make it out to be. Each side has its fair share of pros and cons, ups and downs. As is true with so many aspects of growing there is no easy, clear cut answer to the question of what is right and what is wrong. At the end of the day each individual grower must figure out not only what works well for them but what is also the most productive approach to their garden. A solution many growers have found successful is to use a well balanced bled of organic and synthetic products. The organic products help create and maintain a healthy, biologically active environment in the root zone where as the synthetic products promote adequate and reliable soil fertility, resulting in a plant that is nutritionally sound and healthy. This approach, when done thoughtfully, can create vigorous and sustained growth both within the rooting medium and above.

Kyle Ladenburger is a Garden & Greenhouse contributing editor and can be contacted at

Want more information? Read these articles:

Brushing Up on Your “Fertilizer-Speak”

Calcium: The Forgotten Fertilizer

Dry Fertilizers vs Liquid Fertilizers

How to Select the Best Orchid Fertilizer

Organic Fertilizer Overview

The Fertilizer Value of Worm Castings

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