Homegrown: Compost 101

I cringe when I see people discard banana peels, egg shells and other potential compostables.

Composting not only saves landfill space, but can benefit the soil in your garden.

Linn County Master Gardener, Lisa Slattery, provides advice on how to get started with your own compost pile:

This week I incorporated three truck loads of compost into my gardens. A good friend asked me why I used it and what did it do? Great question!

So what is compost? Iowa State University describes compost as "an organic amendment used to improve the physical, chemical and biological properties of soils." Adding compost helps sandy soil hold more moisture and improves drainage and aeration of heavy clay soils. It's also a slow release nutrient for plants but it doesn't replace fertilizer. If you add compost to your soil year after year you'll create excellent soil that is easier to work with and plants will thrive.

Where to start? Compost is made when a mixture of yard and garden waste materials plus kitchen scraps decompose. Materials appropriate for composting include leaves, grass clippings, straw and hay, finely chopped tree and shrub prunings and kitchen scraps like vegetable trimmings, coffee grounds and eggshells. Don't add meat scraps, bones, grease, whole eggs, or dairy products. Dog, cat and human waste shouldn't be used because of the possibility of transmitting diseases. It's also best not to compost diseased plant material or weeds that have gone to seed in home compost because if the temperature of the compost pile doesn't reach 150° to 160°F the weed seeds and disease organisms won't be destroyed. ISU recommends making your compost pile about 3' by 3' by 3' up to 5' x5' by 5' any smaller and it will dry too quickly, any larger and it will be hard to turn.

How fast your compost pile produces (the decomposition rate) is determined by several things. Compost piles must have nitrogen, water, oxygen and some soil to decompose properly. Decomposition will be effected by the type and combination of materials, moisture levels and how often the pile is turned. Plan to turn the compost pile once a week during growing season and make sure there is sufficient water. If the pile just sits there it'll take a long time to decompose into compost. If you don't have items high in nitrogen like grass clippings you can add fertilizer with nitrogen to the pile since it is required for decomposition. If grass is treated with a herbicide wait for two to three mowings after application before composting the clippings.

If managed properly, the average compost pile can be producing product in approximately 2 to 4 months. Compost will be dark brown, have a nice earthy odor and you won't be able to pick out individual items that went into the pile. However, if compost is started in the fall it probably won't be decomposed for spring.

Place your compost in an area that is out of the way but accessible to water. Partial shade is preferred as full sun may have a drying effect and full shade may slow decomposition. Build your pile in layers with a 6-8 inch layer of plant material and kitchen waste topped with 1-2 inches of garden soil and keep layering until turning.

My grandfather added lime to his compost pile but it isn't necessary since most plant materials in Iowa are almost neutral. But if a soil test in your garden shows too much acid then you could add agricultural lime. Ideal moisture levels run about 40-60 percent for the good microbes to multiple and decompose materials but don't make it soggy, it should feel like a damp sponge to the touch. If there isn't enough moisture the pile can get too hot. For more specifics on composting visit Iowa State University Extension website.