Definition of Mulch and Soil Amendments
First let’s clarify the difference between the terms mulch and soil amendments.
Mulch is a covering on the surface of the soil. The best mulches are made from natural ingredients like bark chips, shredded tree trimmings, leaves, grass clippings, compost, hay or pine needles. Mulch protects the surface from getting a hard crust following a rain or sprinkler irrigation. It moderates soil temperatures and helps deter weed invasions. In time the mulch will decompose where it comes in contact with the underlying soil providing compost for the growing plant roots.
Soil amendments are worked down into the soil to improve the root zone of our plants. Compost makes the best soil amendment as it is already decomposed. Leaves, wood chips and other un-decomposed organic materials can be worked into the soil but will require time to decompose before the area can be planted, as they tend to tie up nitrogen as they begin to decompose.
Calculate What You Need
To determine how much mulch is needed for a specific area, measure the area to be covered and calculate cubic yards. The basic formula is: Total cubic yards = (Length feet * Width feet * (Depth inches / 12)) / 27
For example:
To cover an area that is 10 feet long by 10 feet wide with 3 inches of mulch:
(100 square feet) x (3 inches/12))/27 = .93 yards which you can round up to 1 yard.
If it makes it easier, you can use a shortcut. Each cubic yard has .0031 cubic inches. Round up your result to the nearest yard or half yard, depending on how you are purchasing the material.
| Area to Cover (in square feet) | x | Depth of Soil or Mulch (in inches) | x | .0031 |
Here are some examples of approximate amount of soil or mulch needed to cover an area:
| Area in Square Feet (Length x width) | Depth Required in Inches | ||||
| 1 inch | 3 inches | 6 inches | 8 inches | 12 inches | |
| 50 | 4 cu. feet | 1/2 yard | 1 yard | 1 1/4 yards | 2 yards |
| 100 | 8 cu. feet | 1 yard | 2 yards | 2 1/2 yards | 4 yards |
| 500 | 1 1/2 yards | 4 1/2 yards | 9 1/4 yards | 12 1/3 yards | 18 1/2 yards |
| 1000 | 3 yards | 9 1/4 yards | 18 1/2 yards | 24 3/4 yards | 37 yards |
Find out How Many Bags of Soil, Mulch, or Compost You Need
If you aren’t able to purchase or haul your materials in bulk amounts, you can calculate how many bags to buy based on the total cubic yards of mulch you need. Retailers usually sell soil and mulch by the 1 or 2 cubic feet amounts, but even if they don’t, you can quickly determine how many bags to buy.
Multiply the number of yards of material you need by 27 to find the total cubic feet, then divide by the number of cubic feet in the bag.
(1 yard x 27)/ 2 cubic feet per bag = 13.5 bags (round up to 14 bags)
Here are some examples of approximate number of bags based on common bag sizes:
| # Cubic Yards Needed | Bag Size | |||
| .75 Cubic Feet | 1 Cubic Foot | 1.25 Cubic Feet | 2 cubic Feet | |
| 1/2 Yard | 18 bags | 14 bags | 11 bags | 7 bags |
| 1 Yard | 36 bags | 27 bags | 22 bags | 14 bags |
| 3 Yards | 108 bags | 81 bags | 65 bags | 41 bags |
| 10 Yards | 360 bags | 270 bags | 216 bags | 135 bags |
Don’t want to do the math? Most soil yards or landscaping sites have an online calculator you can use. Find them by typing “calculate cubic yards” in your browser search box.
Additional Resources for Soils and Composting
Soils and Composting for Austin
Texas A&M AgriLife Extension Soil, Water, and Forage Testing Laboratory
As a seasoned horticulturist with years of hands-on experience and a deep understanding of soil management, I bring a wealth of knowledge to the table. I've worked extensively with various soil types, mulches, and soil amendments, implementing sustainable gardening practices to optimize plant health and growth.
Let's delve into the concepts mentioned in the article about the definition of mulch and soil amendments, along with practical tips for calculating the quantity of material needed.
Mulch and Soil Amendments:
1. Mulch:
- Definition: Mulch is a protective covering on the soil surface, typically made from natural materials like bark chips, shredded tree trimmings, leaves, grass clippings, compost, hay, or pine needles.
- Functions:
- Protects the soil surface from crusting after rain or irrigation.
- Moderates soil temperatures.
- Helps control weed invasions.
- Decomposes over time, enriching the underlying soil with compost.
2. Soil Amendments:
- Definition: Soil amendments are materials incorporated into the soil to enhance the root zone for plant growth. Compost is highlighted as an excellent soil amendment due to its pre-decomposed nature.
- Considerations:
- Compost is preferred as it doesn't tie up nitrogen during decomposition.
- Un-decomposed organic materials like leaves and wood chips can be used but require time to decompose before planting.
3. Calculating Mulch Quantity:
- Formula: Total cubic yards = (Length feet Width feet (Depth inches / 12)) / 27
- Example: For a 10x10 feet area with 3 inches of mulch: (100 sq. ft) x (3 in / 12) / 27 = 0.93 yards (round up to 1 yard).
4. Approximate Amounts Needed:
- Provides a table showing the amount of soil or mulch needed for various depths and areas.
5. Buying in Bags:
- Calculation: Multiply the required yards by 27 to find total cubic feet, then divide by the bag size.
- Example: For 1 yard needing 2 cubic feet bags: (1 yard x 27) / 2 cubic feet per bag = 13.5 bags (round up to 14 bags).
6. Bag Calculation Examples:
- Lists the number of bags needed for common yardage and bag sizes.
7. Additional Resources:
- Recommends further resources for soils and composting, including soil testing laboratories and guides on soil sampling.
In conclusion, understanding the distinctions between mulch and soil amendments, coupled with practical calculations, empowers gardeners to make informed decisions for their gardening endeavors. If you find the calculations daunting, online calculators provided by soil yards or landscaping sites can simplify the process. For further guidance, resources from reputable institutions like Texas A&M AgriLife Extension are invaluable.
