Use of composted manures and plant materials in farming has a history almost as long as farming itself. California farmers enjoy access to high-quality compost and mulch products from a variety of feedstocks 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.
Governor Brown's administration has recognized the importance of soil health, establishing the Healthy Soils Initiative. With CalRecycle and the California Department of Food and Agriculture as lead agencies, goals for this initiative include building soil organic matter, increasing climate resiliency and maintaining high yields.
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
- Climate change drives farmer-focused digestate and compost in agriculture research in the United Kingdom. Digestate and compost in agriculture or the DC-Agri Project, is a four year research project on the use of quality anaerobic digestate and compost in agriculture. The results of this research show that digestate and compost can improve soil fertility and provide valuable plant nutrients.
- GO Compost is making up to 15,000 tons of compost per year from tomato skins and seeds, and other locally sourced materials. GO stands for the partners in the project, General Mills and OLAM.
- Crop Yields and Plant Health for Growing Processing Tomatoes: Processing tomatoes grown with 10 tons per acre of composted poultry manure achieved yields 9 to 22 percent above controls, according to new research funded by the California Tomato Research Institute and carried out by the University of California Cooperative Extension. Yield increases were most pronounced for soils with potassium levels below 200 ppm.
- Compost use in large-scale production of salad greens: Michael Brautovich has five watchwords when it comes to purchasing compost for Earthbound Farm, one of the nation’s largest growers of fresh salad mix and organic vegetables. “Quality, safe, consistent, mature, organic” said Brautovich, Earthbound’s senior manager for quality, food safety and organic integrity. “We are looking for compost free of chemical, physical, and biological contaminants.”
- Compost use on California winery: The Joseph Phelps Winery: Using compost to help capture "terroir". Sustainable agriculture practices contribute to production of world class wines.
- Compost use on California rangeland:
Carbon Project is performing a long-term experiment using large quantities of compost to improve forage on California rangeland. Early results suggest significant improvements in forage quality and quantity, benefits to native perennial
grasses, and significant soil carbon sequestration. The work includes a suite of farm management practices to compliment compost application in a manner that builds soil carbon and soil health and improves productivity. Each farm has developed
a comprehensive carbon
farm plan, including known climate-beneficial practices such as windbreaks, riparian and range management improvements, and grass, plant and tree establishment.
- Read about the ‘4
per Thousand’ initiative, launched at the Paris Climate conference, to implement practical actions on soil carbon storage and encourage ag and other stakeholders to transition towards a productive, highly resilient agriculture that creates
jobs and ensures sustainability.
- Read about the ‘4 per Thousand’ initiative, launched at the Paris Climate conference, to implement practical actions on soil carbon storage and encourage ag and other stakeholders to transition towards a productive, highly resilient agriculture that creates jobs and ensures sustainability.
- CalRecycle projects:
- Agricultural demonstrations.
- Impact of Compost Application on Soil Erosion and Water Quality. David M. Crohn, University of California Riverside. March 2011.
- Compost Demonstration Project, Placer County: Use of Compost as Primary Erosion Control Material.
Scientific Research on Compost Use
- Broccoli and lettuce. Scientists, growers assess trade-offs in use of tillage, cover crops and compost. Jackson L, Ramirez I, Yokota R, Fennimore S, Koike S, Henderson D, Chaney W, Klonsky K. 2003. Use of cover crops and compost increased soil quality in irrigated, intensive production of lettuce and broccoli in the Salinas Valley.
- Changes in Soil Properties and Carbon Content Following Compost Application: Results of On-farm Sampling, Sally Brown and Matt Cotton, Compost Science and Utilization (2011). Benefits associated with compost use in agricultural soils. Using a response variable to normalize across sites, improvements were seen in total carbon, reduced bulk density, increased microbial activity, total nitrogen (in comparison to control soils), water holding capacity, and water infiltration rate.
- Climate change mitigation. A Lifecycle Model to Evaluate Carbon Sequestration Potential and Greenhouse Gas Dynamics of Managed Grasslands, Marcia S. DeLonge, Rebecca Ryals, and Whendee L. Silver, University of California Berkeley, Department of Environmental Science, Policy, and Management. Applications of composted organic matter to grasslands can contribute to climate change mitigation while sustaining productive lands and reducing waste loads.
- Composting for Soil Borne Disease Control, Compost on strawberry production, Margaret Lloyd, UC Davis (2014).
- Corn production. Residual Effects of Compost Applied to Sweet Corn Over Two Crop Seasons, T.L Jackson, W. Brinton, D. T. Handley, M. Hutchinson, M. Hutton. Compost application increased plant height, ear length and marketable yield compared to no compost application.
- Forage quality and yield. Amending Pasture Soils Improves Forage Quality and Economic Return: An Organic Dairy Case Study C.A. Daley, Ph.D., California State University, Chico, College of Agriculture, Organic Dairy Program. A long-term soil remediation field trial to study the effect of a basic soil amendment
program on forage quality and yield, with an emphasis on the economic return that would result from added milk production.
- Long-Term Effects of Compost and Cover Crops on Soil Phosphorus in Two California Agroecosystems. Maltais-Landry, G., Scow, K., Brennan, E., & Vitousek, P. (2015). Long-Term Effects of Compost and Cover Crops on Soil Phosphorus in Two California Agroecosystems.
- Potato production. Economic Potential of Compost Amendment as an Alternative to Irrigation in Maine Potato Production Systems, John M. Halloran, Robert P. Larkin, Sherri L. DeFauw, O. Modesto Olanya, Zhongqi He, U.S. Department of Agriculture: National Agricultural Library. Compost is a potentially viable substitute to irrigation for potato in the northeastern U.S. Such potential is highly dependent on suitable compost sources and application costs.
- Quantifying Benefits Associated with Land Application of Organic Residuals in Washington State, Sally Brown, Kate Kurtz, Andy Bary, and Craig Cogger, Environmental Science & Technology. This study was conducted to quantify soil carbon storage, nitrogen concentration, available phosphorus, and water holding capacity across a range of sites in Washington State.
- Research to Evaluate Environmental Impacts of Direct Land Application of Uncomposted Green and Woody Wastes on Air and Water Quality. 2015. Burger, M., Zhu, X., Green, P., CalRecycle/UC Davis. This field and laboratory study measured greenhouse gas and VOC emissions from chipped and ground uncomposted organic materials applied directly to agricultural lands, assessed migration of chemical constituents into the soil and soil water, and characterized the composition of these materials from seven facilities throughout the state.
- Research to Evaluate Nitrous Oxide (N2O) Emissions from
Compost In Support Of AB 32 Scoping Plan Composting Measure. 2015. Horwath, W., Zhu Barker, X., Bailey, S., Burger, M., Kent, E., Paw U, K.T.. CalRecycle/UC Davis. This study measured greenhouse gas emissions associated with the composting
process and application of composted green materials to agricultural lands. UC Davis researchers studied emissions from traditional open windrow and aerated static pile composting, as well as those associated with the application of compost to
tomato fields and almond orchards.
- Where to Buy Compost in California
- Other Tools
- Alternative Farming Systems Information Center: Specializes in library services related to aspects of alternative agriculture, such as sustainable crop and livestock farming systems, ecological pest management, and organic production, certification, and marketing.
- BioCycle article: Applying Compost in Mainstream Agriculture, Ralph Jurgens.
- CalRecycle Composting Regulations
- CalRecycle's Farm and Ranch Cleanup Grants
- Leafy Greens Marketing Agreement: Industry standards for farmers growing salad greens who use manures, composts and other fertilizers.
- Planting Seeds: Food and Farming News from CDFA
- University of California Agriculture Website
- U.S. Department of Agriculture: Natural Resources Conservation Service Website
- U.S. Food and Drug Administration (FDA) Produce Safety Rule: Questions and answers on the proposed rule for produce safety. This rule is one of five proposed rules that would be foundational in the food safety system mandated by the FDA Food Safety Modernization Act.