By HOWARD STENN

As we say in the recycling business, “One person’s trash is another’s gold.” Vashon farmers and gardeners can mine a lot of gold from the nuggets left behind by our neighbors’ horses, goats, llamas and other ruminants.

Manure left in a pen or piled in the woods can create bad smells, attract flies and rats and contaminate streams and groundwater.

Bit when handled properly, manure can be a great resource for farmers and gardeners. Aged manure makes clay soil easier to cultivate, better drained and more productive. Amazingly, manure also slows drainage in sandy soil, reducing the need to water and fertilize. Manure also adds nutrients and feeds beneficial soil life.

A horse produces almost 11 cubic yards of manure each year. That’s over 2,500 yards from just the 250 island horses that King Conservation District (KCD) works with on pasture and waste management — and there are many more, plus cows, goats, sheep and llamas.

Considering it costs over $40 per yard for compost delivered from the mainland, manure is almost as valuable as gold. But before you rush off to add manure to your soil — or try selling that pile in the back 40 for $1,150 an ounce (today’s gold price) — there are a few things you should know.

First, manure is not the same as the compost you buy. Compost is a regulated product that has been processed to destroy weeds, seeds and plant and animal diseases. It has also been cured so that it won’t cause nutrient imbalances or burn plants.

Fresh (or home-composted) manure contains seeds or rhizomes of weeds that can take over a garden. It may also cause nutrient imbalances in your soil

Gathering manure when it is fresh, wetting it if it is dry and stacking it in covered piles can help. But as many gardeners have learned, when using manure, be prepared to pull weeds. A neighbor solves this by spreading aged manure over his annual garden in winter, letting the weeds germinate in early spring, then rototilling a few times before planting.

If you have manure that you want to make into a better soil amendment, look up Washington State University’s Strategies for Livestock Manure Management brochure. For more hands-on assistance, KCD can help develop a management plan and even pay for storage bins. Information about its programs is available online. It also hosts a list of livestock owners with manure to share. There are currently no Vashon sources listed, so tell your horsey friends and neighbors about it.

The second thing to know is that manure is not a substitute for fertilizer. Even manure that is few years old can tie up all the nitrogen when mixed into soil. I recently relearned this the hard way after mixing several yards of dark, aged manure and sawdust into vegetable beds and then watching healthy transplants stop growing. Fish emulsion to the rescue.

For the best results, mix aged manure into garden soil at least a few weeks before you plan to plant, and then test the soil to see what is needed. Fertilizing based on tests ensures you add enough nitrogen, but not excess nutrients that may end up in local waters. KCD can also help with soil testing, offering up to five free soil tests per property, and Oregon State Extension has a list of regional soil labs.

A final word of warning: Timothy and other hay can contain traces of a herbicide that persists in compost for up 18 months at levels that stunt the growth of seedling peas, potatoes and other crops. Though it is not toxic to people or other animals, and most plants will outgrow the effects, it can set back crops. This is not a problem for manure from livestock fed exclusively on island pastures and hay, but most horses get some imported feed. For an test to see if compost or manure is okay, Google “WSU herbicide bioassay.”

Technically, it would be easy to compost much of Vashon’s livestock manure to produce an economical, home-grown alternative to imported material. Many livestock owners and gardeners are already making the connections, but there is still a lot of manure creating problems — and a lot of compost riding the ferries.

More communication between livestock owners and growers is part of the solution. Organized composting and marketing of manure from larger livestock operations may be another part. Let’s talk about it and explore this possibility seriously.

— Howard Stenn is a composting, water conservation and horticultural consultant and  is on the board of the Vashon Island Growers Association (VIGA). This column is part of a series by VIGA members.