Compost and fertilizer are both used to add nutrients to soil, but they work in different ways. Understanding the distinctions between compost and fertilizer can help gardeners make informed choices about amending their soil.
What is Compost?
Compost is organic matter that has been broken down and decomposed by microorganisms. Good compost contains a mixture of brown and green plant-based materials like leaves, grass clippings, straw, and food scraps.
As these materials decompose, compost becomes a crumbly, earthy-smelling, nutrient-rich substance. Compost adds organic matter to soil, improving soil structure and moisture retention. It also provides a slow, steady release of macronutrients like nitrogen, phosphorus, and potassium, as well as micronutrients.
Adding compost to soil has numerous benefits:
- Improves soil structure and texture
- Increases nutrient content in soil
- Boosts populations of beneficial microorganisms
- Helps soil retain moisture
- Allows better drainage and aeration
- Buffers soil pH
- Reduces soil erosion
- Suppresses plant diseases
Compost is created through the natural process of decomposition. Making good compost relies on maintaining proper carbon-to-nitrogen ratios, oxygen flow, and moisture levels. Commercial compost facilities carefully monitor conditions to create consistent, high-quality compost. Home composting requires more effort to achieve usable compost.
What is Fertilizer?
Fertilizer is any material added to soil to provide essential nutrients for plant growth. Most fertilizers are man-made products that contain specific NPK ratios of nitrogen (N), phosphorus (P), and potassium (K). The numbers on a fertilizer label (i.e. 10-10-10 or 5-10-5) indicate the percentage of each of the primary macronutrients it contains.
Other nutrients like calcium, magnesium, sulfur, and micronutrients may also be included in specialty fertilizer blends tailored for certain plants or soils. Quick-release chemical fertilizers provide an immediate nutrient boost when applied, while slow-release fertilizers slowly break down over time.
There are pros and cons to using fertilizer:
Pros:
- Provides concentrated doses of essential plant nutrients
- Allows precise control over nutrient levels
- Offers options for quick or timed nutrient release
- Often inexpensive and readily available
Cons:
- Does not improve overall soil structure and biology
- Excess fertilizer can burn plants or leach into waterways
- Must be reapplied regularly to maintain effects
- Overreliance can damage soil health over time
Compost vs. Fertilizer: Key Differences
While compost and fertilizer both provide nutrients to plants, there are some important distinctions between these soil amendments:
- Origin: Compost is derived from organic wastes like plant debris, manure, and food scraps. Fertilizer is synthetically manufactured or mined.
- Nutrient content: Compost contains a wide range of macro and micronutrients, although in low concentrations. Fertilizer has higher levels of specific macronutrients like NPK.
- Nutrient release: Nutrients in compost are released slowly over months as it breaks down. Fertilizer nutrients are either quick-release or timed-release.
- Soil structure: Compost improves soil texture, balances pH, and boosts beneficial microbes. Fertilizer does not enhance soil structure or biology.
- Sustainability: Composting recycles organic wastes. Chemical fertilizer production consumes fossil fuels and minerals.
- Cost: Compost can often be made at home for free, or purchased inexpensively. Fertilizer usually costs more per volume.
- Environmental impact: Compost improves the soil ecosystem. Excess fertilizer can pollute waterways with nutrient runoff.
When to Use Compost vs. Fertilizer
In most cases, compost and fertilizer work best when used together as part of an integrated soil management plan.
Use compost to build healthy soil structure and biology. Compost improves the soil’s ability to receive, retain, and release nutrients. It provides a broad spectrum of organic nutrients that enrich soil over the long-term.
Use fertilizers to provide an immediate boost of specific macronutrients when rapid green growth is desired. Fertilizers can supplement compost to optimize nutrient levels for plant needs.
New garden beds often benefit from initially adding 1-3 inches of compost to enrich the native soil. Existing beds should get 1-2 inches of fresh compost annually. Fertilizer can then be applied at planting time and throughout the growing season based on plant requirements.
Compost and Fertilizer Application Tips
Follow these tips to get the most out of compost and fertilizer:
- Always do a soil test first to understand your soil chemistry and nutrient needs.
- For new beds, mix 1-3 inches of compost into the top 6-12 inches of native soil.
- For existing beds, apply 1-2 inches of compost and gently till it into the topsoil.
- When adding fertilizer, follow package directions and calibrate your spreader. Less is often more.
- Apply slow-release fertilizers at planting time. Use fast-acting ones to give plants a mid-season boost or correct deficiencies.
- Side-dress growing plants with extra compost or fertilizer by digging it into the soil around the roots.
- Rake any compost or fertilizer that lands on plant leaves back into the soil to prevent burning.
- After adding amendments, water thoroughly to help nutrients penetrate the root zone.
An Ideal Combo: Compost Plus Targeted Fertilizer
Combining quality compost with precisely timed applications of purpose-specific fertilizers provides the best nourishment for healthy, productive gardens.
The compost delivers a spectrum of organic nutrients that feed the living soil ecosystem. It improves moisture retention, drainage, and nutrient absorption in the root zone.
Meanwhile, the selected fertilizer provides a targeted boost of the essential macronutrients that plants need most at key growth stages. Together, compost and fertilizer support optimal plant performance.
Frequently Asked Questions About Compost vs. Fertilizer
Should I use compost or fertilizer in my garden?
Using both compost and fertilizer is recommended to build healthy soil, provide a broad range of organic nutrients, and give plants the specific minerals they need. Apply compost regularly to nourish the soil, and use focalized fertilizers as needed for plant nutrition.
What are the main differences between compost and fertilizer?
The main differences are that compost is derived from decomposed organic matter and improves overall soil quality, while fertilizer is synthetically produced and provides higher concentrations of select macronutrients.
Is compost better than fertilizer?
Compost and fertilizer serve different primary purposes. Compost promotes long-term soil health and fertility. Fertilizer provides immediate plant-available nutrients. Using both together provides complementary benefits.
Should I fertilize after adding compost?
Yes, it is usually recommended to add compost to build up your overall soil, then follow up with targeted fertilizer applications to give plants a nutrient boost when needed. The compost will improve the soil’s ability to receive and release the fertilizer nutrients.
Can too much compost harm plants?
Too much compost could potentially cause salt buildups that damage plant roots. As a general rule, do not add more than 1-3 inches of compost to existing beds per year, and thoroughly mix it into the native soil to dilute salt concentrations.
What is the best fertilizer to use with compost?
Compost is compatible with most fertilizers. Choose a fertilizer with an NPK ratio suited to your plants’ needs. Controlled-release fertilizers are a good pairing to provide a gradual nutrient supply along with the compost.
Conclusion
Compost and fertilizer can both improve soil health and provide essential nutrients to plants. While compost takes longer to break down and release nutrients, it delivers lasting enhancement of overall soil structure and biology. Fertilizers give an immediate boost of key macronutrients to accelerate plant growth.
Ideally, gardeners should aim to building up their soil with regular compost additions, along with strategic fertilizer applications timed to the needs of their crops. This integrated approach combines the soil-nourishing power of compost with the fast mineral nutrients of fertilizer for optimal plant performance.