How to Apply Compost
Compost is an incredibly versatile resource that can be used for everything from growing healthy foods and beautiful landscapes, to erosion control, stormwater management, and environmental remediation.
By growing healthy soil with compost, we can create resilient communities and strong, regenerative economies. Thanks for joining us in the ground work of building healthy soils!
Step 1: Determine Your Use Case
The type and quantity of compost you need is determined by your end use. Are you landscaping your backyard or growing food in a school garden? Using compost for bioremediation? To sequester carbon or save water? Or on construction projects as a stormwater management BMP?
Ron Alexander worked with the Compost Research and Education Foundation to develop factsheets about best practices and benefits of using compost in 10 different scenarios: Bioretention Media, Edible Gardens, Erosion Control Blanket, Landscape Gardens, Row Crop Production, Supplementing Plant Nutrition, Topsoil Manufacturing, Turf Installation, Turf Maintenance, and Upgrading Marginal Soils.
Compost Solutions
Because compost is such a versatile resource, it can be difficult to decide what kind of compost to use for your needs - and to learn how to use it properly in that context. CalRecycle developed a Compost and Mulch Toolbox as a repository for many different uses of compost and mulch, depending on your needs.
Step 2: Acquire Compost
Compost is heavy, which makes it an inherently local product. Delivery costs can be prohibitive, so it's important to find a composter near your project location.
Certain government contracts or grant programs require specific certifications for compost use. The Seal of Testing Assurance (STA) Certification program meets many of these requirements, especially for CalTrans and the CDFA Healthy Soils Grant program.
Compost.ag is another compost map resource, developed by Zero Foodprint, to help locate composters of different types, who may or may not have the requisite certifications.
Compost Quality Considerations
Keep in mind that not all compost is the same, and different compost serves different uses! Fine compost is typically screened to 3/8 inches, and can be incorporated into garden beds or applied to turf grass. Coarser compost (3 inch minus) can be used as a mulch. Organic agriculture requires OMRI certified compost. Some compost is made from municipal organic waste, which comes from the green bin.
As with all products, free is not always better. Compost prices can vary widely, and specialty projects may call for specialty compost.
Help improve compost quality by reviewing your compost purchase with the rating form below!
Step 3: Apply Compost
The "last mile" is the hardest. You've decided to use compost, figured out where to buy it - but how do you actually get it where it needs to go?
Applying compost to a home garden can be done by hand, but larger applications require specialized technology. Farms may use different spreaders, depending on whether they're prepping a field for row crops, applying compost to grazing land, or adding compost to a vineyard to orchard.
Stormwater managers and erosion control specialists may benefit from compost blower trucks, which can spread compost and mulch on slopes or fill compost socks on site.
ACP is currently working to collect more data on compost application service providers in California. If this is you, please get in touch!
Additional Resources on Compost Use
Compost Use on Turf Grass
Using Compost to Improve Turf Performance
A simple guide to using compost on turf grass, developed by Penn State Cooperative Extension. This tool kit includes basic guidelines for evaluating the suitability of different compost products on turf, an overview of common testing results that are favorable for turf, and a brief overview of different methods of applying compost.
Using Manure Based Composts in Turf Maintenance
This Fact Sheet summarizes the results of a study conducted by Cornell Waste Management Institute and the Cornell Department of Horticulture. This research was completed on four sites in western and southeast NYS over several years to assess compost use in turf maintenance. Dairy and poultry manure-based composts were topdressed at 2 rates (1/4 inch and 1/2 inch) on replicated plots along with control plots once in Year 1 and twice in Years 2 and 3. The impact on soils and turf quality was analyzed and is summarized here.
Case Study: Palm Springs Compost on Turfgrass
The City of Palm Springs Office of Sustainability contracted Community Works Design Group (CWDG) to provide analysis and recommendations on the use of compost to achieve the procurement goals for Palm Springs. The climate, weather, and plant material present within Palm Springs precludes the use of organic mulch, while biofuel and electricity solutions require expensive and intensive infrastructure to produce. Compost has been identified as a recycled product which can be applied throughout the City- owned property to meet the procurement goal, and the Palm Springs Disposal Services indicates they have the infrastructure to convert the recycled green waste into nutrient-rich compost.
The City of Palm Springs identified 12 city owned properties to be assessed for the potential of compost incorporation. Community Works visited these sites, collected soil samples, sent the soil samples off for analysis, estimated the square footage of turf areas of the site, and calculated how much compost could applied to each site.
Compost and Water Conservation
Compost and Mulch for Water Conservation Lit Review
The research performed on the effect of high organic matter for various cultivars using both irrigation and non-irrigated systems continues to grow. What is evident from the research data to date, however, is that the water holding capacity is greatly increased by adding organic matter. This, in turn, translates into 2-2.5 times the plant available water compared to un- amended soils. This is significant for California growing applications (agriculture, landscape and irrigated working lands), which constitute over 80 percent of its managed lands, and 90% of California’s human (i.e. non-environmental) water use. The opportunity to save water in agriculture and landscape, is therefore very significant, especially in drought years.
Managing Soils for Water: How Five Principles of Soil Health Support Water Infiltration and Storage
Explains how clay particles released from soil aggregates by rainfall seal the soil surface and prevent water infiltration, and how cover crops and compost prevent this process. ATTRA Good foundational document for farmer education.
Compost in Agriculture
UC Davis Agricultural Sustainability Institute
Soil Health Research (Russell Ranch) Long-running research at Russell Ranch showing compost application significantly increases soil aggregate stability and water infiltration rates. Also tracks cover crops and compost combined versus conventional systems.
UC Davis College of Agricultural & Environmental Sciences
Soil Health Overview of UC Davis partnerships with farmers and water districts on soil health, including the Agricultural Groundwater Recharge and Banking team studying intentional winter flooding of agricultural fields to replenish groundwater.
Rangeland Compost Application
Marin Carbon Project - Carbon Sequestration
Compost on Rangelands (UC Berkeley Silver Lab) A landmark California study where a single application of compost on grazed rangelands resulted in measurable soil carbon gains that lasted for years. A 2023 Journal of Soil and Water Conservation paper found compost amendments improved aboveground production by over 40%, below ground carbon content by 50%, aggregate stability by about 42%, and water retention by about 18%.
East Stanislaus RCD – Statewide Compost Rangeland Trials
Directly relevant to the San Joaquin Valley. Jeff Borum, a soil health conservationist with the East Stanislaus Resource Conservation District, has been experimenting with compost applications at 16 locations throughout California — including Tulare County — measuring water infiltration rates, compaction, forage production, soil carbon, and pH. Preliminary data is promising, with drier sites like the Kaweah Oaks preserve in Tulare County showing greater increases in soil carbon.
Interested in learning more?
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