Compost Use in General Landscaping Applications

//Compost Use in General Landscaping Applications

Compost is such a unique product and it provides many benefits to the soil, to plants, the environment and to the ‘pocketbook’ of the end user. In the next two articles, we are going to discuss the use of compost in soil and water conservation, and protection (e.g., storm water management, erosion control and engineered soils), but before that, let’s discuss the product itself and its usage in general landscape applications. Commercially produced bulk compost is readily available in most parts of Eastern Pennsylvania and Delaware and should be considered in every project where either topsoil or soil amendments will be used. Let’s look at some basic information about compost.

What is Compost?

Compost is the product resulting from the controlled biological decomposition of organic material. This organic matter is broken down and sanitized through the generation of heat resulting from the intense activity of billions of microbes growing and reproducing. Good quality compost is stabilized to the point where it is beneficial to plant growth and bears little physical resemblance to the organic residuals from which it came. These organic residuals may include yard trimmings and food by-products, as well as agricultural by-products such as manure and mushroom soil. Compost is used primarily for its soil conditioning properties, but can also provide significant levels of slowly releasing plant nutrients.

How is Compost Produced?

All compost, is produced through the activity of aerobic (oxygen requiring) microorganisms. These “bugs” need oxygen, moisture and food in order to grow and multiply. Their activity generates heat, water vapor and carbon dioxide as they transform raw organic residuals into a stable soil conditioner. The natural decomposition process is greatly accelerated when these resources are maintained at optimal levels by controlling the feed stock “recipe” and properly managing the daily activities of the composting process.

Compost Benefits

The use of compost, as previously mentioned, can provide many benefits. It improves the physical, chemical and biological properties of the soil and media to which it is blended. Some of these benefits are listed in the table below:

Benefits of Compost Use

  • Improves the soil structure, porosity, and bulk density – creating a better plant root environment
  • Increases moisture infiltration and permeability of heavy soils – improving drainage and reducing erosion and runoff
  • Improves the moisture holding capacity of light soils – reducing water loss and nutrient leaching and helping to conserve water
  • Improves and stabilizes soil pH – creating a better environment for overall plant health
  • Improves cation exchange capacity (CEC) of soils – improving their ability to retain nutrients for plant use
  • Supplies a variety of macro and micro nutrients – reducing initial fertilizer needs in some applications
  • Supplies significant quantities of stabilized organic matter – the essence of ‘healthy soil’
  • Supplies beneficial microorganisms to the soil – improving nutrient uptake and suppressing certain soil-borne diseases
  • Binds and degrades specific pollutants – a new?, pollution reducing benefit 

General Landscaping Applications

Compost is very versatile, and as such, can be used for a variety of applications, including:

General soil amending for planting bed, garden or turf establishment

  1. Till existing soil to a depth of 6”-8”.
  2. Add 2” of compost and mix well with the site soil.
  3. Plant or seed and water well.

Planting individual trees, shrubs or plants

  1. Prepare your planting hole. Make sure that the hole’s diameter is approximately 3 times the diameter of the root ball.
  2. Mix 1 part compost with 2 or 3 parts soil removed from the planting hole.
  3. Place plant in hole, backfill with blended soil, and water well.


  1. Apply a 2” to 3” layer of coarse compost as a surface mulch around trees, shrubs and flower gardens.

Outdoor potting media

  1. Prepare a high organic, nutrient rich outdoor plant potting soil by mixing 1 part compost (by volume), 1 part pine bark fines, and 1 part sand.
  2. Plant and water well the first several times you add water.

Always refer to instructional information provided by your specific compost manufacturer, specifically for their product, and always understand the quality of the soil and compost you are working with. For compost, the easiest way to do this is by specifying and using only US Composting Council Seal of Testing Assurance program certified compost. These compost products are tested regularly, using specialize laboratories, and they analyze for a variety of parameters; including pH, electrical conductivity, stability, maturity and much more. For additional information on the STA Program, or to find a list of participants, go to (click on “programs’, then ‘sta’.)

Mr. Alexander has over 30 years of experience working with compost and other organic recycled products on large-scale construction projects, and is a member of the ASLA. He began his career in Philadelphia, and is now the President of R. Alexander Associates, Inc., a consulting company specializing in product development for organic recycled products. He is the author of the ‘Field Guide to Compost Use’, American Association of State Highway and Transportation Officials’ Erosion Control Specifications for Compost, and ‘Landscape Architecture Specifications for Compost Utilization’.

He provides technical assistance to Laurel Valley Soils, a large composter in Avondale ( Contact Ron Alexander at or 919-367-8350 if you are interested in additional information on compost use or a related Lunch & Learn.

2017-02-28T16:21:05+00:00Feb 28 2017|Chapter News|