California Department of Resources Recycling and Recovery (CalRecycle)

Organic Materials Management

Compost Use in Agriculture

Use of composted manures and plant materials in farming has a history almost as long as farming itself. California farmers enjoy access to a large and diverse composting infrastructure, making high-quality compost and mulch products from a variety of feedstocks available virtually everywhere in the state. California compost facilities permitted in accordance with state law and CalRecycle regulations, and inspected by our network of local enforcement agencies (LEA), meet high standards for pathogen reduction and testing of final product. Additionally, compost facilities selling to organic food producers are inspected annually by the California Department of Food and Agriculture for strict adherence to National Organic Program regulations.

Regular use of compost brings many benefits to the farmer. Some of these benefits have been studied. Other benefits are more difficult to quantify, and will vary for farmers based on frequency and amount of compost applied, soil type, crop rotations, and other factors. They include:

  • Increased soil water holding capacity and reduced runoff
  • Beneficial micro-organisms to improve soil health
  • Addition of humus
  • Addition of organic matter and carbon sequestration
  • Improved soil tilth

Compost provides low levels of all primary, secondary and micronutrients. Many micronutrients become depleted from agricultural lands over time and may not be replenished with conventional fertilizers. Compiled analyses of more than 1,600 compost samples from the southwestern United States performed by Soil Control Lab found average levels of these micronutrients.

Case Studies of Compost Use

Scientific Research on Compost Use



Last updated: May 15, 2014
Organic Materials Management