And Where To Find Good Quality Compost
As spring arrives, it’s time to replenish our garden soil. Whether homemade or commercial, good quality compost nourishes the soil so it can in turn nourish our plants. Since compost can vary markedly from batch to batch, commercial facilities test their compost frequently. Incoming material is shredded, mixed, and tested for pH, clopyralid (a persistent herbicide), moisture content, and carbon-to-nitrogen ratio.
After composting for several months, it’s screened and retested for clopyralid, heavy metals, and other compounds, as well as pH, nitrogen, organic content and what’s called ‘sharps’ (pieces of plastic, glass, etc.). It’s then tested monthly for pathogens like E. coli, and quarterly for pesticide residues.
Peas & Beans Tell The Tale
Home composters can use a simple bioassay to test for clopyralid and weed seeds. Mix equal parts of compost and potting soil, then sow a few peas and green beans. If weed seeds are present, they’ll soon sprout. If clopyralid is present, the legumes will display pesticide damage (yellowed and distorted foliage) when the second or third sets of true leaves appears.
Compost contaminated with clopyralid can be used on lawns and some ornamentals, but not in edible gardens. Even in tiny amounts, clopyralid damages or kills plants in the legume (peas, beans, alders) nightshade (peppers, eggplant, petunias) and composite families (asters, daisies, sunflowers). These families include hundreds of edibles and common ornamentals, so use contaminated compost with care. (Good news? It will kill Scotch broom!)
Hot Can Harm, Cool Is Comforting
Home compost makers can evaluate compost quality in several other ways. Immature compost is very hot and lively, full of degraders that can harm plant roots. Finished compost must be well under 120 degrees and free from heat loving microbes. Mature compost may steam a bit when shoveled, but can be comfortably handled.
Good quality compost smells pleasantly earthy, not rotten or stinky. Compost that smells like ammonia is immature and needs more time (up to 6 months) before it is safe to use. When commercial compost has a funky smell, it may just be coming from the bottom of a huge pile. If soggy material smells anaerobic, turn it several times to air it out (it won’t hurt the garden).
No Obvious Residues, Please
Commercial compost should never include identifiable chunks of raw material. If you spot an eggshell or fruit rind in homemade compost, place a wire screen over a wheelbarrow. Rub your compost through it with the back of a flat shovel and it will look like the pro’s.
Compost so expensive because composting is both an art and a science. This supposedly simple recycling process is actually a lengthy and costly one. All that testing (now mandatory) is one reason; compost MUST be free of dangerous contaminants. Another is that large-scale compost facilities repair and replace expensive grinders and mixers and screeners on a regular basis.
A Fine Local Resource For Kitsapers
Feed stock materials must be carried to the site, processed many times and ways, then delivered to the customer. When gas and oil prices are high, the cost of compost goes up accordingly.
With Emu Topsoil closed, many gardeners are seeking new sources for good compost. I really like Oly Mountain Fish Compost, which recycles locally sourced fish waste, yard waste, and native hardwood logging waste. Certified organic and made in Belfair, Oly Mountain Fish Compost is aged 2 years. This nearly odorless compost provides a steady, slow release of nitrogen and other nutrients.
Oly Mountain Fish Compost is available in bags and in bulk at many retail outlets throughout Western Washington. For more information, call (206) 940-8807 or use the link below to find retail and bulk outlets near you.