Mulch is not a fertilizer. Decomposing mulch is not capable of delivering a substantial amount of nutrients to your plants quickly. Although organic mulch gradually breaks down and provides a small number of nutrients to the soil, it does not match the benefits of fertilizer. Mulch does, however, help soil retain moisture and nutrients. So, it’s essential to protect your soil with a layer of mulch.
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What is the Difference Between Mulch and Fertilizer?
Mulch is a ground covering made of organic or inorganic materials. It serves as an insulating barrier that protects soil from heat, cold, evaporation, and invasive weeds. Think of mulch as a coat of armor for your garden soil—it keeps the good things protected and keeps the bad things out. Your mulch can be made of anything from shredded leaves, to nut hulls, to bark, to rocks or recycled rubber.
- Fertilizer and mulch are very different gardening materials.
- Mulch is meant to protect your soil from temperature changes, evaporation, and weed invasion.
- Fertilizer introduces essential nutrients to the soil to fuel plant growth.
- Fertilizer and mulch can be used together for better garden health.
- Make sure to add fertilizer and mulch in the correct order for the best results.
Fertilizer refers to any product designed to provide key soil nutrients to your lawn or garden. Compost is a form of fertilizer. So are granular and liquid fertilizers. Most fertilizer delivers 3 key ingredients: nitrogen, phosphorus, and potassium. These 3 ingredients are essential for plant growth. So, think of fertilizer as fuel for the plants you’re growing. It ensures they grow healthy roots, leaves, and fruits.
What are the Benefits of Mulch?
The first benefit of mulch is that it suppresses weed growth. A 3–4 inch deep (7.5–10 cm) layer of mulch will smother any weed seeds that attempt to sprout in your garden. In addition, any weed seeds that are blown into your garden will not be able to reach the soil and take root as long as you have mulch. So, mulch is essential for keeping your garden areas weed-free.
- Suppresses weed growth.
- Retains soil moisture.
- Keeps soil at optimal temperatures for plant health.
Mulch also helps your soil retain moisture. Sunlight and high temperatures can quickly evaporate water from your soil, starving your plants. Mulch forms a barrier so that the soil has enough moisture to keep your plants growing strong, even in intense heat. As an added bonus, mulch helps regulate soil temperatures. Cold nights or hot days can damage plant roots, but mulch prevents extreme soil temperatures. Mulch can save your plants from frost or heat damage.
What are the Benefits of Fertilizer?
Fertilizer’s main benefit is that it aids in plant growth. The nitrogen in fertilizer encourages leaf and stem growth. Phosphorus helps plants build strong roots. Potassium content in fertilizer is essential for plants that produce fruits, vegetables, and flowers. Without these elements in the soil, your plants will struggle, die, or be prone to disease.
- Provides key nutrients for plant growth.
- Prevents plant death and disease.
- Introduces micronutrients to the soil so you can grow healthy produce.
- Boosts the population of healthy soil microbes.
Fertilizer also contains micronutrients including, iron, calcium, and copper. These nutrients are not only essential for plant growth, but they’re also important for humans. If you are growing food in your garden, it’s critical to fertilize the soil so that your homegrown fruits and vegetables are full of vitamins and minerals.
Does Mulch Add Nutrients to the Soil?
Organic mulches do add nutrients to your lawn or garden bed. However, they add only small amounts of nutrients very slowly. For instance, grass clippings used as mulch are equivalent to a 4-1-2 fertilizer. That is 4% nitrogen, 1% phosphorus, and 2% potassium by weight. In comparison, your average garden fertilizer has a nutrient balance of 10-10-10. This means that 10% of its weight is taken up by each of these 3 key ingredients.
- Some mulches return trace amounts of nutrients to the soil as they decompose.
- The nutrient content provided by mulch is very small compared to fertilizer.
- Grass clippings and leaf mulch are the fastest-decomposing mulches that add soil nutrients.
- Wood mulch, bark, and nut hulls break down slowly, so they are not a reliable source of soil nutrients.
- Rock and rubber mulches do not decompose or provide nutrients to the soil.
Grass clippings are a fast-decomposing mulch that provides some nutrients to the soil. Other organic mulches are less effective. Wood chips and bark mulch decompose very slowly, so they are unlikely to add significant nutrients to the soil. Inorganic mulch, such as pebbles or gravel, does not add any nutrients to the soil.
Is Mulch a Soil Amendment?
Mulch is not a soil amendment because it is added on top of the soil, not mixed into the soil. Soil amendments are compounds mixed with the soil to improve it. For instance, compost is mixed with soil to improve water retention and boost the population of soil microbes. Lime is mixed with soil to reduce acidity.
- Mulch is not a soil amendment.
- Soil amendments are compounds mixed into the soil to improve it.
- Mulch protects improved soil, but does not alter the soil itself.
- Lime, compost, and sulfur are common examples of soil amendments.
Mulch is a soil covering that protects the ground in your flower or vegetable garden. If you have recently improved your soil by adding an amendment, such as lime, humic acid, or sulfur, mulch will ensure your soil retains the benefits of the amendment.
Can You Use Old Mulch as Fertilizer?
Some forms of mulch can add trace nutrients to the soil, but they do not take the place of a complete fertilizer. Pine needles, shredded leaves, straw, and grass clippings are all types of mulch that decompose quickly and provide some nutrients to the ground. However, they will not dramatically improve soil health. Use these mulches to protect the soil. Any nutrients you get from them is an added bonus.
- Mulches do not contain enough nutrients on their own to work as fertilizer.
- If your mulch is made of organic materials, it will only add a small amount of nutrients.
- You can turn mulch into fertilizer by using it as a compost ingredient.
If you want to transform old mulch into fertilizer, consider composting. Composting grass or leaves with manure and other ingredients creates a rich fertilizer. You’ll get the most benefit by using your old mulch in compost.
Is Mulch Considered Fertilizer?
If you’re wondering whether the mulch in your flower beds can also be considered a fertilizer, keep these facts in mind:
- Mulch does not have nearly as many nutrients or minerals as true fertilizer.
- Most mulches made of organic materials break down slowly, providing nutrients at a slow rate that won’t help your plants significantly.
- Mulch is primarily designed to protect the soil from weed invasion, water evaporation, and temperature changes.
- Fertilizer should always be the first choice if you want to add nutrients to the soil.
Although mulch is not a fertilizer, it is still essential for soil health. A layer of mulch on the soil surface will help prevent weeds and keep your plants from suffering during drought or cold snaps.