Compost and fertilizer are both used to provide nutrients to plants and improve soil health. However, there are some key differences between the two. This article will compare and contrast compost and fertilizer, looking at the following aspects:
What is Compost?
Compost is organic matter that has been broken down and decomposed by microorganisms. Good compost contains a mixture of:
- Brown materials (carbon-rich): dead leaves, branches, twigs
- Green materials (nitrogen-rich): grass clippings, fruit and vegetable scraps, coffee grounds
As these materials decompose, they form a dark, crumbly, earthy-smelling material called humus. This finished compost is packed with nutrients and beneficial microbes that plants thrive on.
Making compost relies on natural processes to break down organic matter over time. The decomposition happens more quickly if the compost pile has a proper balance of carbon, nitrogen, air, and moisture. Turning or mixing the compost helps speed things along. Depending on factors like the size and contents of the pile, compost can take anywhere from 2 months to 2 years to fully decompose.
What is Fertilizer?
Fertilizer is any material added to soil or plant leaves to supply nutrients and improve plant growth. There are two main types of fertilizers:
Organic fertilizers come from plant or animal sources, such as compost, manure, fish emulsion, and bone meal. During decomposition, the organic matter releases nutrients slowly over an extended period.
Chemical/inorganic fertilizers are man-made products produced through industrial processes. These concentrated fertilizers release nutrients quickly into the soil. Common chemical types include urea, ammonium nitrate, and superphosphate.
While organic sources break down naturally, chemical fertilizers do not degrade. The nutrients remain in the soil until absorbed by plant roots. Excess chemical fertilizers can build up and wash away into water sources, leading to pollution.
Key Differences Between Compost and Fertilizer
While both provide plant nutrients, compost and fertilizer work in different ways. Here are some of the main differences:
- Purpose: Compost feeds and nourishes the soil, improving the overall soil structure and ability to retain moisture and nutrients. Fertilizer feeds the plants, supplying specific macro- and micronutrients to promote growth and productivity.
- Nutrient content: Compost contains a wide array of major, minor, and trace elements, including nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, and more. The nutrient ratios vary based on the inputs. Fertilizers have set, measured ratios of N-P-K and other elements tailored to a crop’s needs.
- Application: Compost can be worked into garden beds or spread around plants, trees, and shrubs. There’s no risk of “burning” plants if too much compost is applied. With fertilizers, careful dosage is needed based on soil tests. Too much fertilizer can damage plants.
- Timing: Compost releases nutrients slowly over months or years. Fertilizer nutrients are available to plants right away after application.
- Microbial life: Compost introduces beneficial bacteria, fungi, and other microbes into the soil. These microorganisms break down organic matter, releasing more nutrients for plant uptake. Fertilizers do not contain live microbes and only add mineral nutrients.
- Cost: Compost can be made at home using garden and kitchen scraps. Purchased compost may cost $20-$40 per cubic yard. Fertilizer prices vary widely, from $15 for a 50-pound bag up to $100 or more.
- Environmental impact: Compost is considered very eco-friendly and sustainable. Chemical fertilizers require fossil fuels and minerals to manufacture. Excess fertilizers contribute to water pollution problems like algal blooms. However, careful fertilizer applications can avoid environmental issues.
When to Choose Compost vs. Fertilizer
With their different strengths and functions, compost and fertilizer work best when used together as part of an integrated soil fertility plan. Here are some guidelines on when to choose each:
Use compost when:
- Starting a new garden bed or landscaping area – it will enrich the soil prior to planting
- Introducing beneficial microbes to the soil
- Improving moisture retention and nutrient holding capacity
- Providing nutrients for general plant health and vigor
- Building long-term soil quality and tilth
Use fertilizer when:
- Soil tests show specific nutrient deficiencies
- Targeted nutrients are needed by high-demand crops like tomatoes, peppers, and corn
- Fast-release nutrients are desired for plant establishment and rapid growth
- Nutrient ratios need to be carefully controlled (for example, more phosphorus than nitrogen for root growth)
- Supplying micronutrients lacking in the soil such as zinc or boron
Many gardeners apply 1-2 inches of compost to beds each spring and fall. They also use organic granular fertilizers at planting time and liquid fertilizers during the growing season when plants need a nutrient boost. This combined approach leverages the unique advantages of both compost and fertilizer.
Compost and Fertilizer Use in Gardening
When used properly, compost and fertilizer are incredibly beneficial in the garden. Here’s a closer look at how each can be used effectively:
Using Compost in the Garden
Compost helps gardens in the following ways:
- Builds healthy soil – Compost contains organic matter that improves soil structure. This creates a better environment for plants, microbes, and helpful soil organisms like earthworms.
- Provides a slow-release nutrient source – The nutrients in compost break down over months and years. This results in a steady supply of nitrogen, phosphorus, and minerals.
- Increases nutrient retention – The organic matter in compost holds positively charged ions that cling to plant nutrients. This prevents the nutrients from washing away.
- Promotes beneficial microbes – Compost is filled with helpful bacteria and fungi that control soil-borne diseases, break down toxins, and produce plant growth hormones.
- Supplies humic acids – Humic substances in finished compost aid nutrient uptake, drought tolerance, and seed germination.
To use compost in the garden, apply a 2-4 inch layer over beds and work it into the top 6 inches of soil. Reapply yearly or as needed based on soil tests. When transplanting plants, add a few handfuls of compost to each hole.
Using Fertilizer in the Garden
Chemical and organic fertilizers support plants in the following ways:
- Provide targeted nutrition – With soil testing, the exact nutrients a plant needs can be determined. The right fertilizer can supply nitrogen for leaves and shoots, phosphorus for roots and flowers, potassium for disease resistance, or micronutrients like iron, manganese, or zinc.
- Allow for greater control – Fertilizers can be applied at specific rates and formulas tailored to a crop. Release times can be chosen, from quick nitrogen boosts to slow-release formulas. This control is not possible with compost.
- Offer application methods – Fertilizers come in many forms: liquids, spikes, granules, powders, and time-release capsules. There are application methods suitable for any setting.
- Help correct deficiencies fast – Unlike compost, fertilizers provide an immediate nutrient boost when plants show deficiency symptoms during the growing season.
Follow package instructions carefully when using fertilizers. Overapplication can cause fertilizer burn. Test soils yearly to determine actual nutrient needs. Side-dress growing plants every few weeks with a diluted liquid fertilizer to replenish nutrients used up by crops.
Case Study 1: New Garden Bed Installation
Jill wants to plant a new vegetable garden. The site is on compacted clay soil in full sun. Soil tests show very low organic matter, nitrogen, phosphorus and potassium levels.
To prepare the bed, Jill spreads a 4-inch layer of high-quality compost over the entire area. She then uses a rototiller to work it into the top 8 inches of native soil. This adds organic matter to improve aeration, drainage and moisture retention in the poor soil. It also introduces beneficial microbes and slowly-available nutrients the soil is lacking.
Two weeks before planting, Jill applies an organic granular fertilizer according to soil test recommendations. This fertilizer has an NPK ratio ideal for vegetables (like 5-10-10 or 5-10-5). The fertilizer will supply nitrogen, phosphorus and potassium to fuel plant growth once the seeds start growing.
By using both compost and fertilizer, Jill transformed poor soil into a fertile, nutrient-rich garden bed ready for planting. The compost created long-term improvements, while the fertilizer gives an immediate nutritional boost to new seedlings.
Case Study 2: Established Perennial Landscape
Mike has a mature ornamental garden with established trees, shrubs and perennials. The plants look stunted and are showing signs of chlorosis (yellowing leaves). Soil tests indicate the soil is too acidic and deficient in nitrogen, iron, manganese and zinc.
To rejuvenate the garden, Mike spreads 1-2 inches of compost around all plants to increase organic matter in the soil and provide a general nutrient boost. He also applies an acidic fertilizer (ammonium sulfate) to lower soil pH to a level preferable for his azaleas, rhododendrons and hydrangeas.
Additionally, Mike sprays the chlorotic foliage with liquid chelated iron, manganese, and zinc to quickly correct the corresponding deficiencies. The liquid micronutrients are rapidly absorbed by plant leaves and used by the plants.
Within a few weeks, Mike’s garden returns to its former glory. By using both compost and customized fertilizers, he resolved immediate issues and provided long-term soil enrichment.
Compost vs Manure, Bone Meal and Other Organic Amendments
Besides commercial fertilizers, other organic soil amendments can be used to provide plant nutrients. Some common choices are:
- Manure – Livestock manure adds nitrogen, phosphorus and potassium in an organic form. It must be composted before using to avoid burning plants.
- Bone meal – Ground animal bones supply phosphorus and calcium. Bone meal releases nutrients slowly over several months.
- Blood meal – Dried, powdered animal blood is high in nitrogen to stimulate leafy growth. Blood meal works quickly but does not last as long as compost.
- Fish emulsion – Made from fish waste and oils, this liquid fertilizer provides nitrogen, phosphorus and trace nutrients. The odor takes some getting used to.
- Seaweed extracts – Kelp, seaweed and fish extracts contain growth-promoting hormones, micronutrients, carbohydrates, and proteins to improve plant health.
These organic amendments can be used along with compost and fertilizer. For example, bone meal might be worked into a planting hole to encourage root growth. Fish emulsion can be applied as a supplemental nitrogen source.
Compost offers the widest range of balanced, slow-release nutrients compared to these single-ingredient amendments. But the other organic products can fill in nutritional gaps as needed.
Should You Use Compost or Fertilizer in Your Garden?
The simple answer is to use both compost and fertilizer in most gardens. Here’s why:
- Compost feeds the soil food web and improves overall soil health. Fertilizer cannot match compost’s wide-ranging soil benefits.
- Fertilizer feeds plants directly by efficiently supplying specific macro- and micronutrients. Compost’s nutrients are more general.
- Together they complement each other. Compost creates the foundation for healthy soil. Fertilizer gives plants the nutrients they need to thrive in that healthy soil.
If you had to choose just one, compost would be the best overall choice. Added annually, compost will meet basic plant nutrient needs while vastly improving your soil. However, the ideal integrated plan uses both organic and chemical fertilizers as needed in addition to regular compost applications.
So don’t think of it as an either/or proposition. Harness the power of both compost and fertilizers for a thriving, productive garden! With the right combination approach, your plants will grow bigger, stronger, and more bountiful than if using just one or the other.
FAQs About Compost vs. Fertilizer
Here are answers to some frequently asked questions about the differences between compost and fertilizer:
Should I use compost or fertilizer in my vegetable garden?
Use both! Apply 1-2 inches of finished compost to garden beds each spring and fall. Test soils yearly and use organic or chemical fertilizers at planting time and as needed during the growing season. The compost feeds the soil while the fertilizers target plant nutrient needs.
What provides more nutrients, compost or fertilizer?
Fertilizers provide higher concentrations of immediately available nitrogen, phosphorus, and potassium. But compost releases a wide spectrum of major and micronutrients over a longer timeframe. In terms of total nutrients by volume, compost wins out over the long run.
Do plants grow faster with fertilizer or compost?
Fertilizers will make plants grow faster because their nutrients are instantly accessible. Compost’s nutrients break down slowly over time. Think of fertilizers like a nitro-fueled dragster, while compost provides the steady, long-haul fuel source.
Can compost totally replace fertilizer in the garden?
Using only compost is not ideal for plants with high nutrient demands like tomatoes, peppers, and squash. These plants need fertilizer’s quick nitrogen release at key growth stages. Apply compost for overall soil improvement and use targeted organic or chemical fertilizers as needed.
Is homemade compost as good as store-bought fertilizer?
Homemade compost boasts many bonuses store-bought fertilizers can’t match – more microbes and organic matter, for instance. But compost alone may not contain high enough nutrient concentrations to maximize plant growth and production. Use both homemade compost and quality fertilizers.
When should I apply compost vs fertilizer to my lawn?
Apply 1/4 to 1/2 inch of compost over lawns in early spring and fall to enrich the soil. Fertilize at least twice per year – in spring at green-up and in fall before grass goes dormant. Choose a fertilizer with slow-release nitrogen to avoid surge growth and thatch buildup.
conclusion
Compost and fertilizer serve different purposes in gardening and soil management. Compost, which is a mixture of decomposed organic matter, improves soil structure, nutrient retention, and supports beneficial microorganisms.
It is a long-term soil amendment that enhances the overall health of the soil. Fertilizers, on the other hand, are designed to provide specific nutrients to plants in a more concentrated form. They are used to supplement the nutrients that plants need for growth, and their composition is more rigid to match the exact needs of the plants.
Compost and fertilizer are complementary, and both play an essential role in keeping your crops and the soil healthy. Compost should be added annually to maintain soil health, while fertilizer is better used in spring and when plants are at the peak of their growing cycle.
Incorrect use of fertilizers can lead to soil and plant damage, while compost is a more environmentally friendly and sustainable option. However, compost alone may not be sufficient for plants with high nutrient demands, and additional fertilizer may be necessary