- Author: Help Desk Team
We have all heard of this magical stuff called compost. But what is it? Where does it come from? Why is it so important for our gardens? The reason compost is so important is because it enriches our soil, adding important nutrients that are used by plants for growth. When we create compost, we are breaking down organic matter into a form that provides a rich amendment for the soil and promotes healthy microbial activity. With these nutrients, plants can better resist disease and insects. In addition, compost increases water retention and helps reduce soil diseases. And it can be rewarding to make your own!
What do you need for great compost?
Green material—Yard waste, kitchen vegetable scraps, coffee grounds, or fresh grass clippings. This fresh waste provides the compost's nitrogen content. Do not add meat, dairy products, oil, fat, or dog or cat manure.
Brown material—Dried leaves, torn up newspaper, pieces of cardboard boxes, or shredded paper bags. This dry material provides the carbon content. The smaller you cut the pieces, the faster the composting process will be.
How much of each—Start with equal parts of green and brown material and add up to twice as much brown material as green. Don't use more green material than brown.
Water—Water each layer of the pile to the level of a wrung out wet sponge. If the bin is exposed to rain and gets too much water, you might need to cover it.
Air—Turn the pile every few days, if possible, but at least once a week for air circulation. A pitchfork works well for turning. In addition to letting the pile “breathe”, it helps prevent problems with flies and rodents. Turning the pile helps maintain an optimal temperature, while mixing prevents dense clumping of some materials such as wet green grass.
Temperature—Heat in the pile is generated by bacteria feeding on the green material. Temperatures above 140°F will kill many pathogens and weed seeds and will also accelerate decomposition for faster composting (see below). A compost thermometer with a long probe gives good information about when to turn the pile and when to water it.
Different methods of composting—Factors to consider when choosing a method include the time and energy needed to maintain the pile, the amount of compost needed, and the time needed to achieve the finished product. The pile needs to be at least 3 feet square to generate enough heat for decomposition. You can build the compost pile right on the ground but if you build a structure to contain the pile, it should be 3–5 feet with one side open for easy access to build or turn the pile. Sun or shade does not matter as the temperature of the pile depends on its composition, not exposure to the sun. Other composting containers can include a closed container, like a rolling barrel, or an open bin composter. There are many ways to make compost: underground, above ground, in bins, in boxes, in pits, in bags, in barrels, in strips, in sheets, and in trenches.
Slow composting method (easy but slow)—Continuously add materials to the pile with little or no chopping of materials. Bury ‘green' scraps 6–12 inches in the center of your bin to reduce attracting flies and rodents. Turn and water as desired for finished compost in 12 to 18 months.
Intermediate composting method (a little more work but faster)—Build a 3' x 3' x 3' pile with materials cut into 2-inch pieces. Turn and water the pile weekly without adding more material to get finished compost in 3 to 8 months.
Fast composting method (the most work but finished fastest)—Build a 3' x 3' x 3' pile with materials chopped to ½ to 1½ inch pieces. Check the temperature of the pile every day with a thermometer in the center of the pile. Turn the pile immediately if the temperature is 150 degrees F or above. Turn and water daily while the pile is between 140–150 degrees F. As the pile cools, turn it whenever it reaches 120 degrees F. Once the pile cools below 120 degrees F, turn and water every week for finished compost in 6–8 weeks.
When is the compost done? The pile will shrink, losing about 1/3 of its volume. It will be dark brown and crumbly with an earthy smell. You should no longer be able to tell what each of the individual ingredients was. Allow compost to age for two weeks before you add it to the soil around plants. Or incorporate it into the soil, but don't sow seeds or transplant seedlings for two weeks.
For more details about composting and what materials to use:
https://sacmg.ucanr.edu/files/163139.pdf
For information about how to use compost in the home garden:
https://ucanr.edu/sites/ccmg/files/221120.pdf
This video is from our own composting experts at our demonstration garden in Walnut Creek: https://www.youtube.com/watch?v=E77Yps9K2bw The garden is open to the public on Wednesday mornings April through October. Please stop by and ask questions.
We hope to see you at Our Garden!
Help Desk of the UC Master Gardeners of Contra Costa County (JRB)
- Author: Birgitte Elbeck, UCCE Master Gardener
Starting a compost pile in winter may not be at the top of your to-do list, but it may be just the thing you need to beat the winter doldrums. Your reward will be soil that is more fertile, supporting bigger and heather plants in next summer's garden.
Types of composting: There are two primary ways to compost in the garden. There is the slow ‘cold' method, where you keep piling material in a heap and leave it largely unattended, probably for longer than a year. Then there is the fast ‘hot' method, which is what Master Gardeners recommend. This fast method not only gives you finished compost in 4-6 weeks but also ensures more consistent results and is more likely to kill weed seeds & pathogens. You do not need to run out and buy anything - however, it does require a bit of elbow grease.
Building your ‘hot' pile: Composting relies on the work of many bacteria, fungi, and invertebrates that consume and break down plant matter. They need oxygen to stay alive. This means that your pile must stay fluffy and have air pockets throughout. In addition to air, the micro organisms also need a certain amount of heat to thrive. Together, these two factors mean that a pile should not be so big that the bottom layers are crushed by the weight above, and a pile should not be so small that too much heat from the organisms escapes. Experience shows that a starting pile 3' x 3' x 3' in size will have about the proper proportions. Your pile should be placed directly on the soil and kept in place with a simple ring of fencing material or a similar enclosure. Plastic enclosures are discouraged because the airflow is restricted.
Because you will want the finished compost to provide a well-balanced set of nutrients for your plants, the nutrients in the source material must also be in reasonable balance. The focus specifically is on balancing nitrogen and carbon. For the most part, nitrogen-rich components are green (spinach, for example), and carbon-rich components are brown (wood chips, for example). Click here for additional information about “greens and browns”. Be sure to chop larger pieces to 6” or shorter, as they will compost much faster. Layer several inches of ‘greens' alternating with several inches of ‘browns.' Note that no meat, dairy, or oil should be added to the pile, nor should diseased plant materials or noxious plants with seeds be included.
Pay attention to the water content of your pile. The micro organisms require moist, but not soggy, conditions, and you can achieve this by spraying water on the pile while turning or by placing a cover over it when significant rain is in the forecast.
Turning your pile: Once you have built your pile, wait a number of days for the micro organisms and invertebrates to settle in. Some critters will already be in the raw materials, others will travel up from the soil below, and their activity will start warming the pile. Your active pile will start shrinking, and you can stick your hand toward the pile's center to get a rough feel for the heat level. The desired temperature range is 130 - 160 degrees F; you should turn the pile in that temperature range after about three days. If the pile isn't heating up, it could be that you have not reached a critical mass of materials, or there isn't enough green to go with the brown, or the pile is too green and soggy and needs more browns. Turning your pile with a garden fork onto an adjacent area gives you an opportunity to move the less digested plant materials at the edges toward the middle of the new pile, add water, and introduce new air pockets. A well-managed pile will need to be turned at least once a week, will stay hot for 2 or 3 weeks, and then cool and be recolonized by worms and other soil organisms. In 4-6 weeks, you will have finished compost that can be used to enrich your soil.
Using your compost: Your compost is ready to be spread on your garden beds when it has a crumbly texture with no recognizable bits of vegetation remaining. It will have a fresh, earthy smell. Compost does not need to be worked into the soil; the worms will take care of that for you… But if you are turning your soil, this is a good time to add it.
Links: We encourage you to look at the links to the online material below. The YouTube videos are all very short and practical, while the material on the Master Gardeners' composting page has more technical information.
UC Master Gardeners of Humboldt & Del Norte Counties composting page: https://ucanr.edu/sites/hdnmastergardeners/Resources_for_Home_Gardeners/Composting/
Demonstration videos from the Orange County Master Gardener Program:
What is Composting – https://youtu.be/8Hzz56vV9Mw
How to start a compost pile – https://youtu.be/Z2fIY7eN8fI
How to turn a compost pile – https://youtu.be/lkGRsPm-gt4
What is Hot Method? What is Cold Method? – https://youtu.be/PRpc7o_AaUc
Why are these bugs in my compost pile? - https://youtu.be/VAyM9BjEv9I
Cornell Waste Management Institute, Composting: Balancing Your Greens and Browns https://cwmi.css.cornell.edu/balancing.pdf
- Author: Michelle Leinfelder-Miles
- Author: Radomir Schmidt
The term ‘soil health' has become a common term in agricultural research and management. While most of us are familiar with testing soil for chemical properties, like nutrients, salinity, and pH, soil health also considers soil physical characteristics – like compaction, aggregation, and water infiltration – and biological characteristics – like soil respiration, active carbon, and nitrogen mineralization.
These properties influence the soil's ability to function, and enhancing these properties can improve soil functioning to grow crops and produce ecosystem services. We often relate soil health to management practices like crop rotation, cover cropping, reducing tillage, and adding compost because these have been shown to increase soil functioning in agricultural landscapes. They are also some of the practices that are financially incentivized by the CA Department of Food and Agriculture Healthy Soils Program.
There is a regulatory framework for diverting green waste from landfills to make compost. In 2014, AB 1826 was passed in California, which required businesses to recycle organic wastes and jurisdictions to set up organic waste recycling programs to divert green waste from landfills. In 2016, AB 1383 established organic waste reduction targets (75% reduction by 2025, compared to 2014). The bill also required jurisdictions to do education and outreach. Green waste diversion is expected to reduce greenhouse gas emissions by 4 million metric tons per year and increase food recovery by 20 percent. Agricultural land could serve to receive green waste compost recovered by this regulatory framework.
Our project objectives were to learn whether green waste compost improves soil nutrient status or other soil health characteristics, whether it improves alfalfa yield or quality, or if its application affects greenhouse gas emissions from the system. Alfalfa was chosen for this study because it has a large footprint on the state's agricultural landscape and because it has a high phosphorus (P) and potassium (K) nutrient need which compost could help supply. Also, as a ‘high-traffic' crop, alfalfa soils can have poor physical traits (e.g. compaction, water infiltration), which could potentially be ameliorated with compost.
The study was conducted on commercial farms in Yolo and San Joaquin (SJ) counties. The Yolo site had a mineral soil with high clay content (approximately 50 percent clay), and the SJ soil was a mucky clay with high organic matter (approximately 8 percent). We are comparing two green waste compost rates (3 and 6 tons per acre) to the untreated control. Compost applications were annually (2020-2022) surface-applied in the fall/winter ahead of rain.
Our preliminary results indicate no statistically significant differences in total carbon and nitrogen among treatments (Fig. 2). There is a trend, however, for compost to increase carbon at the Yolo site, which is inherently low in organic matter. An interesting observation about the SJ site, where the soil is inherently low in K, is that the compost increased soil K (statistically significant, Fig. 3). The compost analysis showed that the product was roughly 1 percent K. Therefore, the 3-ton compost rate should have added approximately 50 lb of K per acre, and the 6-ton rate approximately 100 lb of K per acre. Based on the amount of change in soil K and the compost analysis, the compost was likely what contributed to the increase in soil K. This appears to be translating into higher tissue K (Fig. 3), and in turn, higher yields (though neither tissue K nor yield are statistically higher than the control, Fig. 4).
Greenhouse gas emissions have not differed among treatments (Fig. 5), indicating that the carbon that is added by the compost is not being respired from the system. There are higher CO2 emissions at the SJ compared to the Yolo site, which we attribute to the inherently higher carbon of the SJ soil. Additionally, we have observed that the soil acts as a methane sink. This is noteworthy because methane is a more potent greenhouse gas than CO2.
Based on our experiences working on this project, we have the following guidance for growers interested in applying green waste compost. While green waste compost is a relatively cheap input, transport cost can be high. In 2021, we estimated that material plus hauling cost was approximately $27/ton and spreading was an additional $10/ton. The highest demand for compost is in the fall. To ensure availability, growers should aim to purchase compost in the spring or summer and store it on-site until fall. Ordering the compost in spring or summer also tends to result in a higher quality product delivered (i.e. less trashy). Timing compost application can be a challenge (i.e. after all harvests but before soil gets too wet), so having the compost already on-site may help in getting it applied more readily. We still have more data to analyzed for this project, so more information will be forthcoming. We want to thank the growers in Yolo and San Joaquin counties for collaborating with us on this project.
Many backyard gardeners are familiar with composting, a process which recycles yard trimmings along with vegetable and fruit scraps from the kitchen. Compost, a humus-like soil, results from the biological breakdown that occurs from microbial decomposition of organic material. Composting enriches soil, reduces waste in landfills, and conserves water.
To create compost, oxygen and water should also be balanced (50 percent moisture plus 50 percent oxygen). It is important to consider the moisture content of added material such as food scraps and freshly cut grass prior to adding water. Compost should be about as moist as a wrung-out sponge, moist to the touch but not yielding liquid when squeezed. Turning the compost pile aerates it by incorporating oxygen while mixing the materials. Some compost bins available commercially are designed to turn, eliminating the need to building the pile in layers (and also eliminating the need for a hay fork). Bear in mind that high summer temperatures will dry the pile more rapidly.
The length of time for composting depends on several factors: the density and size of the materials, the carbon and nitrogen content, moisture content, aeration, and volume. If you continue to add materials to your compost pile or bin the process will take longer. Turning the pile or bin on a regular basis is the key to having compost ready for your gardening needs. Various sources state that composting can take as little as two weeks and as long as two years. Finished compost is a dark brown, easily crumbled material with a musty smell. The original volume of the compost material is significantly reduced, as is the temperature. The compost now is ready to be used. It can be screened through wire mesh to sift out any larger pieces that have not decomposed.
Once the compost is ready it may be used as mulch around trees, shrubs and other plants. Compost will help suppress weeds while at the same time increasing moisture retention. It may also be incorporated into the soil to improve soil quality. The nutrients in compost are slowly released into the soil and are more easily available to your plants. Once you have started using your own compost you will be convinced that this method of recycling is beneficial on many levels.
For further information, see Pamela M. Geisel and Donna C. Seaver's UC Publication 8367, Composting Is Good for Your Garden and the Environment (PDF).
To learn more about different methods and techniques for making compost, join our Master Gardener workshop on Composting, October 27. For descriptions of this and all the other workshops in the Master Gardeners' Fall Workshop Series, visit our website. All workshops are free, but registration is required.
UC Master Gardeners of Butte County are part of the University of California Cooperative Extension (UCCE) system. To learn more about us and our upcoming events, and for help with gardening in our area visit our website. If you have a gardening question or problem, email the Hotline at mgbutte@ucanr.edu or leave a phone message on our Hotline at 530-552-5812. To speak to a Master Gardener about a gardening issue, or to drop by the MG office during Hotline hours, see the most current information on our Ask Us section of our website.
- Author: Heidi Aufdermaur
We wondered about that too! With this in mind, a group of UC Cooperative Extension Master Gardeners toured the City of Modesto's Compost Facility on 7001 Jennings Road.
Recently in California, there has been an emphasis on green waste collection. This was sparked from recent legislation, AB1383-short-lived climate pollutant reduction strategy--, which in simple terms is to “adopt regulations that achieve the specified targets for reducing organic waste in landfills.” Of course, there is much more to the legislation, but how does this relate to the ‘green cans?' Earlier legislation started the ball rolling, AB 939, AB341 and AB 1826 which focused more on commercial waste.
The main goal of this bill is to reduce the materials taken to our local landfills, which have ever-diminishing space. When organic materials are sent to the landfill, they create methane gas, toxic soup leachate, and hydrogen sulfide (rotten egg gas). Not only that, but homeowners are missing out on a great resource. This compostable material could be kept at home, providing environmental and gardening benefits!
Environmental benefits: Waste reduction, keeping soil fertile, improving air quality, water conservation. Gardening benefits: saves money, enriches soil, contributes to health lifestyle.
How can you benefit from using the green waste from your garden? Come learn more at our workshop. Even if you are already composting or want to learn how to best put that waste to use in your garden, come join us and see how much fun composting can be. We will also talk about vermicomposting and show you how to start your own container of green-waste-eating worms.
Registration Details:
Date: Saturday, September 9, 2023
Time: 9:00 a.m. - 12:00 p.m.
Where: Harvest Hall Rooms AB&C
Register: https://ucanr.edu/compost/2023
The workshop is free! However, if you'd like an 11 gallon compost bin to take home, you can make a $35 donation to our program (while supplies last). Children interested in learning about compost and worms are also welcome at this workshop!
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