Gardeners use compost and fertilizer to achieve the same end – to keep plants growing as vigorously as possible. However, this can obviously create doubts and lead gardening beginners to think that compost is fertilizer, and vice versa.
So, what is the actual difference between them? Which one should you pick to grow your plants? Or should you use both? These are some questions gardening beginners ask when determining what products they should use to grow their plants.
Compost and fertilizer are not the same. Compost is a natural, organic material used to nourish soil structure, helping it absorb nutrients and keep moisture, while simultaneously protecting your plants from pests and diseases. Fertilizer is a non-living substance that can be organic or synthetic and contains nutrients in exact ratios designed to speed up plant growth, but it doesn’t exactly benefit the soil.
In this article, we will define compost and fertilizer, and inspect the differences between them and determine which one you should use by examining the pros and cons of each.
What is Compost?
Compost is made by decomposing organic materials into simpler organic and inorganic compounds by living microorganisms in a process called composting. For example, a banana peel in a waste bin will eventually decompose, as will all organic waste, thanks to the help of microorganisms in the environment that feed on the decaying matter.
Composting is a process that speeds up the decay of organic waste by setting up the ideal conditions for microorganisms to thrive and rapidly decompose that waste. 1 The end-product derived from that process is nutrient-rich soil that can supplement soil structure and help crops, garden plants and trees to grow.
How is Compost Created?
Microorganisms exist everywhere, and to create compost, it’s crucial that you establish the ideal environment for these beings to thrive. That involves having warm temperatures, nutrients, moisture, and plenty of oxygen.
Scientifically, there are three stages in the composting cycles in which different organisms are active 2:
- First stage: Mesophilic microorganisms carry out the initial decomposition stage by rapidly breaking down soluble, readily degradable compounds. The heat they produce causes the compost temperature to rise.
- Second stage: As the temperatures rise, the heat-loving thermophilic organisms take over the compost to break down organic materials into smaller pieces, given that the higher temperatures are more conducive to breaking down proteins, fats, and complex carbohydrates. Employ mechanisms like aeration and turning over the compost pile to prevent temperatures from rising above 149 degrees F (65 degrees C) to keep the microorganisms from dying.
- Third stage: As the supply of energy compounds gets exhausted, the compost temperature gradually decreases and the mesophilic microorganisms once again take over and start breaking down the remaining organic materials into usable humus.
Microorganisms in Compost
We can divide composting microorganisms into two dominant classes, respectively aerobes and anaerobes. 3
Aerobes are bacteria that only survive with oxygen levels of at least five percent to break down organic matter. They consume organic matter and excrete chemicals such as nitrogen, phosphorus and magnesium, which are nutrients plants need to thrive.
Anaerobes are bacteria that don’t need oxygen to thrive. They are not as valuable as aerobes because they can’t break down waste as efficiently. Plus, anaerobes produce chemicals that are occasionally toxic to plants, and they cause compost piles to stink because they release hydrogen sulfide.
Eighty to ninety percent of microorganisms in compost are bacteria. 2 The remaining percentage are fungi, which include molds and yeasts. Besides bacteria and fungi, other creatures such as pill bugs, centipedes, and worms will also find their way to the compost pile, particularly if you have an open-bottomed structure. These creatures also break down organic materials in your compost pile (i.e. food waste) and help convert those materials into nutrient-rich soil.
Vermicomposting is a form of composting that uses various worms species, including red wigglers, white worms, and others to break down organic matter. According to Ecomena, it speeds up conversion of organic waste into nutrient-rich soil. 4
What Goes Into Compost Heaps?
It’s not news that having a proper balance of “greens” and “browns” is essential to create an environment in which microorganisms can thrive. Greens are nitrogen-rich and include items such as grass clippings, fruit and vegetable waste, and coffee grounds. Browns are carbon-rich yard waste, such as dead leaves, branches, and twigs.
A carbon-to-nitrogen ratio between 25 to 1 or 30 to 1 is optimal for rapid composting because they support microorganisms. Microorganisms consume carbon to receive energy and release it as carbon dioxide and heat. Simultaneously, they also feed on nitrogen to grow and reproduce themselves. Having the right balance is essential.
Too much carbon in the compost pile will slow down decomposition and reduce the heat generated by microorganisms because they don’t multiply as quickly. Too much nitrogen can make your compost pile release an ammonia smell and increase its acidity, which can be toxic for some species of microorganisms.
Besides having a balanced carbon-to-nitrogen ratio, you also require proper moisture (between forty and sixty percent) to have enough dampness to prevent microorganisms from becoming dormant and enough to keep the pile with healthy oxygen levels. This balance is crucial because excess moisture can cause aerobic microorganisms to drown, while also causing the pile to smell.
Here are carbon-rich materials you can add to a pile:
- Yard trimmings such as grass, dry leaves, branches, twigs
- Shredded newspaper, paper, cardboard
- Pine needles
- Peanut shells
- Ashes (from wood)
- Corn stalks.
And here are the nitrogen-rich ingredients you can also add:
- Vegetable and fruit scraps
- Coffee grounds
- Grass clippings
There are some materials you can’t compost, for example:
- Yard trimmings treated with chemical pesticides because they may kill off microorganisms
- Pet waste (such as dog or cat feces, and cat litter) because it may contain harmful bacteria, parasites, or viruses
- Dairy products, eggs, fats and oils, meat or fish scraps, because of potential odor problems that attract pests and rodents
- Diseased or insect-infested plants, as the disease or insects may pass onto other plants
- Coal or coal-ash because it might contain substances or properties toxic to plants
Commercial facilities can also collect products like food containers or compostable dinnerware and flatware labelled BPI Certified Compostable. Large commercial facilities can also compost dairy, eggs, and other animal products because they have ways to increase heat and the rate of composting. Homemade piles are more limited.
Pros and Cons of Using Compost
Compost is nature’s way of recycling, and we can reuse useful matter that would otherwise get treated as waste to nourish the soil with brand-new nutrients.
Composting has many advantages, but it also has some complications.
Compost has the following advantages:
- Improves soil quality
- Enhances soil structure
- Cheap to make
- Doesn’t have weird chemicals
- Can lead to higher crop yields
- Leads to less waste
- Better for the environment
- Easy to produce
Improves Soil Quality
Compost can add nutrients to the existing soil mixture, which will translate into a better growth pattern for plants. If you have a garden, using compost is a good way to help your plants grow, while naturally recycling organic household waste.
Naturally, it also comes down to the ingredients used to make the compost.
Enhances Soil Structure
Compost also helps improve soil structure. It will help soil absorb more nutrients and preserve moisture. This is convenient come summer, when the temperature rises and plants need more water to survive.
Cheap to Make
Compost is an inexpensive soil conditioner. If you opt by creating your own compost, using household food waste, the composting costs are close to zero.
The only costs associated to composting are those of an initial structure (i.e. compost bin), which will vary based on its quality. Apart from that, composting is cheap, and you will save money by not having to purchase conventional fertilizer.
Doesn’t Have Weird Chemicals
Compost is a healthy alternative to conventional fertilizers. Because it contains organic waste (i.e. vegetables, fruits and other biodegradable waste), the end-product is also organic, so it will not contribute to soil and groundwater pollution.
Fossil fuels are used to produce conventional fertilizers, which implies the emission of greenhouse gases that lead to global warming. By swapping conventional fertilizers with compost, you can mitigate a lot of these environmental problems.
Can Lead to Higher Crop Yield
Compost leads to a higher crop yield. 5 Since compost improves upon several factors, including water retention, nutrient absorption, and overall structural stability, these all impact plant growth and crop yield. This also depends on the compost’s quality.
Leads to Less Waste
Regular household waste usually ends up in landfills. This is bad for our health and the environment. The runoff from landfills carry toxic chemicals that end up in water channels, which pollute our oceans and water supplies from nearby communities.
By composting your organic waste, you can reduce your overall waste production and prevent a lot from getting to landfills. Not to mention you not having to purchase fertilizers with compost around.
Better for the Environment
Compost is ideal to reduce waste, which is otherwise bad for the environment. Plus, it’s completely organic and doesn’t negatively effect the soil or waterways.
It’s the perfect way to recycle waste and turn it into something that can enrich the soil, giving it the structure to yield crops.
Easy to Produce
Producing compost is rather simple. You don’t need to take a degree or build muscles to produce compost. You just need to have some patience.
Even if you run into some technical issues (i.e. if your compost is too moist), you can easily resolve that by looking at forums or videos on Youtube.
Compost also has disadvantages, including:
- May require an initial investment (to build a structure)
- Efficiency depends on the type of waste you produce
- Unpleasant smell (not always)
- May attract rats, snakes and bugs
- It requires physical labor
- Needs some monitoring
- End-product may take a while to get
- It may spread diseases
May Require an Initial Investment
Composting has many advantages, but there are also some downsides. To compost, you must make an initial investment.
For instance, you need to have a compost bin (it’s what most people typically get), and if you get a Redmon (65 gallon bin) you’ll realize it’s not that expensive and you can get your return on investment quickly, especially by saving on fertilizer.
Efficiency Depends on the Type of Waste Produced
Composting can only be efficient if you have a certain amount of waste, and different waste produced in your household.
For instance, if you produce very little organic food waste (nitrogen), it might be more difficult to get your compost started. If you don’t have any yard trimmings around, that might also be an inconvenient.
May Cause Foul Smell
Having an unbalanced carbon-to-nitrogen ratio can often lead your compost heap to smell. Naturally, this also depends on the type of food waste you recycle.
Foul smell is not only bad for you, but it’s also bad if you live close to your neighbours.
May Attract Rats, Snakes and Bugs
Foul smell may also attract rodents, snakes, and bugs. Bugs aren’t a problem, but rodents and snakes are unwelcome, for several reasons.
Set up your compost in a way that is protective against burrowers (animals that invade your compost from the bottom) or cover it to prevent the smell from spreading.
Requires Physical Labor
Creating compost is a process that requires a significant amount of work, such as turning the compost every few days to maintain proper air circulation.
Depending on the amount of compost you have – it can translate into plenty of work.
Needs some Monitoring
Compost can get excessively moist, stink, invite pests, get overly hot or cold (depending on the season), so you must have your eyes peeled.
Compost must be at optimal temperature to decompose, and that’s something you must monitor periodically. This is especially true if you have no experience.
End-Product May Take a While to Get
Another downside to composting is that it may take a while until organic matter decomposes and converts into usable compost.
Depending on factors such as temperature, input materials, moisture level, and others, it may take anywhere from one month to one year until you have usable compost.
It May Spread Diseases
Bacteria in compost may carry pathogens that spread diseases to other plants. People can also contract diseases from handling compost.
For example, compost often contains bacteria which cause legionellosis, also known as Legionnaire’s disease. An infection can occur from inhaling dust from compost. 6
Bottom line: Compost has many advantages (especially if you learn how to do it properly), but there are also some downsides few people want to deal with.
What is Fertilizer?
Fertilizers are compounds or mixtures delivered as solids, liquids or gases, that supply essential nutrients to crops in soluble forms that are convenient and safe to handle. You can apply fertilizers to the soil or directly to foliage. 7
A plant needs seventeen elements to reach its full nutritional potential. Three elements – carbon, hydrogen, and oxygen – come from air and water. The remaining fourteen come from the soil through the plant’s roots.
Modern day fertilizers contain these elements, which can be divided in three categories:
- Secondary nutrients
The numbers typically referenced in fertilizers are the macronutrients (nitrogen (N), phosphorus (P), and potassium (K), or NPK for short). It’s the proportion of these three nutrients in order and reflects each nutrient’s percentage by weight.
Macronutrients are the major building blocks of all fertilizers and are also the most important nutrients for plant growth.
Even though 78% of the air we breathe is nitrogen, most plants can’t get it from the atmosphere. It has to come through other means. However, it’s difficult to convert nitrogen into a form plants can absorb, and it takes time.
By using nitrogen as nitrates, farmers can supply their crops with all the nitrogen their plants need, whenever they need.
Phosphorus (P) is crucial for photosynthesis, which is the process in which plants convert sunlight into energy. This macronutrient is also important for respiration, cell division and cell growth, aspects that play an important role in plant and fruit development.
The phosphorus in commercial fertilizers is surface mined from phosphate rock, which are naturally occuring sedimentary deposits formed millions of years ago.
The mined phosphate rock then undergoes a few chemical processes and transforms into a form that is bioavailable for plants.
Potassium is available in bananas, avocados, dates and many other fruits. It’s also important for producing high-quality crops, and help them withstand winter.
Potassium is available in the soil but not readily available for plants. The potassium present in today’s fertilizers is mined from deep within the ground as potash.
It’s one of the most abundant crystalline minerals on Earth. Chemical combinations convert potassium into plant food, namely potassium chloride, potassium sulfate and potassium nitrate.
While they’re named “secondary nutrients”, they are still essential for plant growth. It’s just that crops typically need them in lower quantities.
- Calcium (Ca)
Calcium reduces soil acidity and helps with nutrient absorption. It also helps the plant (or crops) resist against disease.
- Magnesium (Mg):
Magnesium is a component of chlorophyll, so it’s essential for photosynthesis. It also helps plants metabolize phosphorus.
- Sulfur (S)
Sulfur is available in the soil but in tiny amounts. Plants rely on sulfur to synthesize amino acids and boost winter resistance.
Micronutrients are only required in trace amounts, but plants can’t do without them.
- Boron (B)
- Chlorine (Cl)
- Copper (Cu)
- Iron (Fe)
- Manganese (Mn)
- Molybdenum (Mo)
- Nickel (Ni)
- Zinc (Zn)
They work together to support different aspects of plant growth, including structural integrity, vitamin production, and increased yields. Boron, Copper, Zinc, and Manganese are the micronutrients most often in short supply in the soil.
Commercial fertilizers typically account for all the different nutrients that sustain plant growth and lead to a better yield.
Pros and Cons of Using Fertilizer
Fertilizers have many advantages, with the most touted one being the increase in crop yield and stability. Not eveything is peaches and roses, though.
Fertilizer has the following advantages:
- Can improve production and yield
- Protects plants against pests
- Fertilizers are cheap
- Can ensure farmers’ livelihood
- Lowers risk of soil erosion
It Can Improve Overall Production and Crop Yield
Fertilizers are best known for increasing overall crop yield. If you plant tomatoes, peppers, or other popular plants in a confined space, it’s more difficult to provide them with the conditions that propel growth.
Not having sufficient space or soil for your plants means you may not provide them with the nutrients they need. Using a fertilizer ensures that your plants grow healthy and produce higher crop yields, regardless of space.
Plants can grow without fertilizers, but they won’t provide the same crop yields if they’re lacking in nutrients.
Protects Plants Against Pests
Fertilizers contain nutrients that make plants resistant against pests or diseases. Though, that is not true for all fertilizers.
A review of 50 years of research identified 135 studies showing more plant damage and/or greater numbers of leaf-chewing insects or mites in nitrogen-fertilized crops, while fewer than 50 studies reported less pest damage. 8
Researches found that high-nitrogen levels in plant tissue can decrease resistance and increase susceptibility to pest attacks.
Fertilizers Are Cheap
Fertilizers are quite cheap. If you visit a store and buy a standard NPK-fertilizer, you’re likely to buy enough fertilizer to supply your crops for many years for a cheap price.
Since a fertilizer also increase overall crop yield, it’s a win-win situation.
Can Ensure Farmers’ Livelihood
Many farmers cannot afford to not use fertilizers, otherwise they risk not generating an income to support their livelihood.
Farmers use fertilizers because it guarantees the stability and predictability of crop yields, unless there is a natural disaster or other extreme conditions.
Using fertilizers gives farmers the opportunity to plan their future with more certainty since their crop yields will be more stable.
Lowers Risk of Soil Erosion
Since plants can optimally grow with the help of fertilizers, that also means they will be stronger and deeply anchored to the ground. They will hold the soil together and reduce the risk of soil erosion.
According to the NSW, reducing fertilizer input can lead to limited plant growth, which can aggravate issues such as soil erosion. 9
Fertilizer also has the following disadvantages:
- Can make the soil less fertile
- Increases soil and groundwater pollution
- Chemical fertilizers are harmful
- May add harmful elements in our food
- May alter ecosystems
Increases Soil and Water Pollution
Despite the several advantages associated with fertilizer use, there are also many issues related to this practice, namely its impact on the environment.
One of the major problems with fertilizer is that it can lead to soil and groundwater pollution. Fertilizers provide plants with crucial nutrients, but they also introduce other toxic substances into the soil, and consequently, our groundwater will suffer as well.
For this reason, there is a call for limiting the use of chemical-based fertilizers and use organic alternatives. Namely, organic fertilizer.
Can Make the Soil Less Fertile
Since chemical fertilizers have toxic substances that pollute the soil, its quality and stability are also affected.
This means that soil can become less fertile over time and lose value. For this reason, farmers should limit fertilizer use so that their lands can continue to be used for agriculture in the future.
Chemical Fertilizers Are Harmful
Unfortunately, chemical fertilizers (which are the most commonly bought) are produced through industrial processes and contain harmful substances that may affect human health in the long run.
Plants extract components from fertilizers, which means if you use too much of a bad fertiizer, that may adversely affect our food.
There are many countries in which farmers have no equipment and may inhale harmful elements present in chemical fertilizers. This may lead to pulmonary diseases and other health problems.
May Alter Ecosystems
Chemical fertilizers can also alter ecosystems.
In fact, it’s not uncommon for fertilizers to end up in aquatic ecosystems by accident.
Because they add extra nutrients and chemicals to the water, they can affect the aquatic environment in several ways. For example, they can cause algal blooms, which leads algae to die off more rapidly. 10
As algae decompose, they remove oxygen from the water, which may kill fish and other aquatic life.
Should You Use Compost or Fertilizer?
Composting is a great way to get rid of your organic food waste and turn it into a conditioner that provides your soil with various benefits.
While it may not be the fastest solution to grow your plants, it’s one that keeps the soil free from harmful substances, while still potentiating crop yield.
Fertilizer, on the other hand, was created to optimize crop yields.
However, too much of it is detrimental to our soil and ecosystems, especially if you opt for cheap chemical fertilizers.
More importantly – you’re not conditioned to use one or the other, since they can complement each other well. The organic matter in compost can absorb the fertilizer’s nutrients until the plants need them. Compost also provides many nutrients that plants need in small amounts, namely boron.
You can choose to use one without the other, or you can take full advantage of both to promote a neatly balanced yet rapid plant growth.
1 – USDA on Composting: https://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/newsroom/features/?cid=nrcs143_023537
2 – Cornell University | Compost Microorganisms: http://compost.css.cornell.edu/microorg.html
3 – Planet Natural: https://www.planetnatural.com/composting-101/making/how-it-works/
4 – ecoMena | What is Vermicomposting: https://www.ecomena.org/vermicomposting/
5 – Taylor & Francis Online: https://www.tandfonline.com/doi/abs/10.1080/03650340.2012.692876
6 – Bay of Plenty District Health Board: https://www.bopdhb.govt.nz/media-publications/2017-media-releases/september-2017/protect-yourself-from-legionnaires%E2%80%99-disease-when-working-with-compost-and-potting-mix/
7 – Angus J.F. (2012) Fertilizer Science and Technology. In: Meyers R.A. (eds) Encyclopedia of Sustainability Science and Technology. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-0851-3_193
8 – Sare.org | https://www.sare.org/publications/manage-insects-on-your-farm/managing-soils-to-minimize-crop-pests/impacts-of-fertilizers-on-insect-pests/
9 – NSW Government | https://www.dpi.nsw.gov.au/agriculture/soils/improvement/environment
10 – Sciencing | https://sciencing.com/how-does-fertilizer-affect-aquatic-ecosystems-13425670.html