- Author: Lee Miller, UCCE Master Gardener
A. There could be several things happening here. For one thing, a compost pile needs to be large enough to trap heat and the general rule of thumb is to have a cubic yard of material – a pile that is 3ft x 3ft x 3ft. A second possible problem is that the pile has insufficient ‘green' materials in it that are needed to provide micro-organisms with sufficient nitrogen to become numerous enough to get the pile warming up. If you are composting a high carbon source such as leaves which have a Carbon:Nitrogen ratio of 60:1, you will need to offset this high ratio with materials with Carbon-to-Nitrogen ratios that are lower than 30:1. The ideal average for a good pile is 30:1. High nitrogen materials are kitchen wastes, coffee grounds, poultry manure, alfalfa meal, and green grass clippings which all have a ratio close to 20:1. Add more of these and see if that cures the problem. If the materials in your pile are too coarse, that could also slow heating and can be cured by chopping materials into smaller pieces with a mower or shredder. However, this is rarely the problem if you are working with grass clippings and leaves. If your pile is anaerobic (see below), temperature will be low and turning the pile will help increase the temperature. There is one other possibility and that is the lack of moisture in the pile. A well-watered pile should be like a wrung-out sponge – moist, but not sopping wet. The pile should get hot, to at least 140ᵒF to kill pathogens and weed seeds.
Q. What materials should not be included in a compost pile?
A. There are some organic materials that are not good to include such as cat and dog feces, cat litter, or diapers which may have pathogens. Invasive weeds like Bermuda grass, dairy products, and greasy stuff; e.g., peanut butter, vegetable oil, butter, bones, meat and fish should either go in the garden waste/garbage or be buried deeply in your orchard or landscape where animals won't dig them up. Eliminating these things will help keep coyotes, raccoons, dogs, cats and rodents out of your compost.
Q. Why does my compost pile smell bad and what can I do to salvage this situation?
A. Your compost pile likely suffers from either being too wet and/or not being turned enough so that you have a smelly, anaerobic (taking place without the benefit of oxygen) composting occurring. If your compost is too wet, less watering is the solution along with turning the pile. The pile being too wet is not usually a problem in our hot, dry climate. In fact, it is usually the opposite – not moist enough. Compost benefits from oxygen which give it an aerobic composting, so turning the pile to add air is important to keep the process aerobic (with the benefit of oxygen). Another factor that will cause a smelly pile is too much nitrogen. This is also rarely the case, but it can happen if you have an overabundance of materials that have a carbon to nitrogen ratio less than 30:1 such as the presence of too many green lawn clippings. The cure for this is to mix in more low nitrogen materials like leaves, straw or wood shavings.