Compost Classification

In the past, landscape architects have requested product bids from suppliers/manufacturers, which included soil amendments that were based on a wide range of specifications/analytical data. Determining the right specification has always been a major dilemma for landscape architects/designers. The actual product and quantity delivered were often in question and hard to verify.

The landscaping industry has long needed a system for classifying soil amendments – some way for landscape architects to determine the best product and quantity required for the specific applications on their project. Let’s face it…the wrong product or wrong application can be very costly to the project and result in poor performance of expensive plants, grasses and trees.

A1 Organics felt it was time to develop a classification system for compost – one which takes into account a number of different parameters and requirements which must be met. By utilizing a compost classification system and standardizing the industry, everyone benefits in the process. Landscape architects will ask for and receive the right compost to make the project a success in the long term by simply identifying the Class (I, II, III, IV) of product needed for the specific application within their project. The landscape contractor will know exactly what kind of compost they need to obtain for the project and can verify its integrity and the volumes delivered to the project. And, finally, the producer is held accountable for their compost by substantiating its quality and classification according to three important areas of evaluation: analytical, manufacturing criteria, and product application/risk.

The Classification System

The current Classification System is divided into four classes:

  1. CLASS I: Fully composted, stabilized and mature product that is generally made from non-manure feedstocks. Will germinate and sustain plants without much risk due to over-application or poor incorporation. May be lower in total nutrient values - kind of your "goof proof" product.
  2. CLASS II:Fully composted, stabilized and mature product that is generally made from manure based feedstocks (dairy, poultry, equestrian, etc.). Proper application quantity and incorporation is important to plant germination and sustainability. Normally has increased level of nutrients and can be used to supplement fertilizer needs.
  3. CLASS III: Partially composted or dehydrated product. May be "shredded" or screened but is not mature or stable.
  4. CLASS IV: Represents raw feedstock materials, such as manure.


  1. Decide what application you will be using the compost for. Soil amendment for sod? Soil amendment for sensitive planting area? Etc.
  2. Decide what quantity do you want to apply. Do I need to add a lot of organic matter? Do I need a lot of nutrients added? How "good" is my soil overall?
  3. Determine the "risk factor" you are willing to accept: Can I properly incorporate the material? Is the slope too steep to allow thorough incorporation?
  4. Choose a classification that best meets your overall objective