The information below is quoted from the Washington State University Cooperative Extension website. It should answer your question. (Source cited on the website: Bob Smith, WSU Master Gardener Program Manager, Thurston County, in The Gardener, Vol. 6, No. 4, Winter 1995-96)

In 1995, three local coffee houses called WSU Extension in Thurston County [Washington] for advice on composting coffee grounds. With the exception of worm bin composting, we were unable to find much information. Our Master Composter and Master Gardener volunteers decided to experiment. They composted about 270 pounds of coffee grounds donated by local espresso bars. They fed roughly 60 pounds to worms while composting the rest in regular bins.

If coffee grounds are not worms's food of choice, they certainly must be high on the list. In appreciation for a meal of ready-to-consume grounds, the worms produced excellent compost. Incorporate coffee grounds soon after brewing into your worm box. This reduced the possibility of the grounds souring and attracting pesky fruit flies.

We also experimented by composting coffee grounds in three types of traditional bins:
1) an enclosed holding bin made of recycled plastic,
2) a three-level wire stacking bin, and
3) a large, round, wire holding bin. Our primary concern was whether the coffee grounds would attract pests.

We incorporated the grounds over a four month period yet experienced only one problem: fruit flies showed up in the enclosed plastic bin almost immediately after we added coffee grounds. In open wire bins, the grounds tended to dry out quickly. Overall, though, we found coffee grounds easy to work with and satisfactory for composting.

Coffee grounds have a carbon-to-nitrogen ratio of 20:1, roughly equivalent to that of grass clippings. After brewing, coffee grounds contain up to 2% nitrogen. For composting purposes, consider coffee grounds green material similar to grass clippings. For brown material, we used leaves and sawdust. In these trials, we used a formula of one part green material (coffee grounds alone or mixed with grass clippings) to two parts leaves, or four parts green material to one part sawdust.

In the Winter 2009 issue of Master Gardener, WSU Extension Horticulturist Linda Chalker-Scott recommends using a thin layer (half an inch or less) of coffee grounds as mulch, topping this with a thicker layer (4 inches) of coarser organic material such as wood chips. She also says that the optimal percentage of coffee grounds in total compost volume should be 10 to 20 percent, and no more. The pH of spent coffee grounds varies, and one cannot assume they are acidic.

Season All Season
Date 2007-12-06
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Below are many links to information about mulch, including several from Pacific Northwest government agencies. Explore these sites for lots of other useful information about gardening!

ABOUT MULCH, types, and uses--Cornell Cooperative Extension (NY)

Union of Concerned Scientists

King County (Washington) Solid Waste Division mulch info
Make the mulch of it!

WSU's King County (Washington) Extension Fact Sheets

INFORMATION FROM THE PACIFIC NORTHWEST (generally useful)
-- Saving Water Partnership (Seattle)
--Marty Wingate article from the SeattlePost-Intelligencer (11-15-2001)
--King Conservation District (Washington), manure share program

COMPOSTING COUNCIL OF CANADA:
Compost.org
MulchingPR

MULCHING TREES
--St. Lawrence County, NY:
Mulching Trees

Season All Season
Date 2008-01-03
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First and most important, it appears mulching is the best organic solution for conditioning clay and heavy soils. Organic soil conditioners include compost, well-rotted animal manures, and natural fertilizers. Planting green manures such as clover, rye grass, or vetch are also effective for breaking up large clods in clay soil over time.

Sheet composting - laying compost over the entire area to be worked and using a fork (or rototiller) to work it into the soil to a depth of 2-4 inches - is cited as an efficient method of soil conditioning. Both books listed below recommend repeating this process at least twice a year, in early spring and in late fall.

Secrets to Great Soil [by Elizabeth P. Stell, 1998, (pbk)] and
The Gardener's Guide to Better Soil [by Gene Logsdon, 1975, (pbk)]

The Saving Water Partnership (the City of Seattle and other government entities) has a website full of information about improving soil.

The site includes Growing Healthy Soil.

Season All Season
Date 2006-12-08
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There are several approaches that you can use to get your new garden ready. One is from Growing Vegetables West of the Cascades by Steve Solomon. He recommends removing the grass, covering it with no more than 1/2 inch of completely rotted compost or 1 inch of raw ruminant manure, and spread agricultural lime at 50 pounds per 1,000 square foot. Do this in early October. Then scatter small-seeded fava bean seed at 6 to 8 pounds per 1,000 square feet. Rototill no more than 2 inches deep and relax until May. In late May you rototill deeply and or spade in the overwintered garden area. Then you can plant.

Another information source, Seattle Tilth's Maritime Northwest Garden Guide, recommends using an annual winter cover crop to improve the soil. It suggests using 85% legume and 15% grain for maximum nitrogen fixation. For the legume, you can use Field peas, Crimson clover, Fava beans or vetch. For the grain you can use cereal rye, winter wheat, spelt or barley. Most of these are applied at about 2 pounds per 1,000 square feet. Again you would rototill or turn under the cover crop in late April or May.

Solomon's method will provide a better total approach. You also should consider having your soil tested to find out what is missing and what your pH level is.

Season Spring
Date 2008-03-27
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It seems that the main source of toxicity is the roots of the walnut tree, rather than the leaves or shells. However, there are still those who believe that there is enough juglone in the leaves that they should be fully composted before use in the garden. Below are excerpts from a Cornell University Extension document on the subject:

"This toxic affect on surrounding plants appears to be related to root contact, as walnut hulls and leaves used as mulch have not shown toxic effects on plant growth. [Warning- Robertson disagrees.] Because Walnut roots do not occupy the surface layers in most soil, many shallow rooted plants growing under walnut trees don't come in contact with the roots and are not affected by them. [Mich]

You've probably always heard that you should never add black walnut sawdust [or wood chips] to the compost pile because the juglone will kill everything that grows in the compost. Abrahams says that's not necessarily true; that juglone is not found in walnut saw dust or wood chips. Nor do dead walnut trees exude juglone. Juglone is harmless to humans so you can go right ahead and safely eat fruit and vegetables grown near walnuts. [Abraham]

Robertson doesn't agree on the use of walnut residue in composting. He has this to say about black walnut saw dust, husks and leaves affecting plants. "Tomatoes growing in clean soil in pots were severely stunted when leaves and nuts fell into the pots while we were on vacation. I know what juglone can do. I have seen a 15-year-old rhododendron killed a few weeks after its owner mulched it with black-walnut husks, and roses injured by an application of compost containing black-walnut sawdust." [Robinson]

The juglone toxin occurs in the leaves, bark, and wood of the walnut but these contain lower concentrations than the roots. Juglone is poorly soluble in water and does not move very far in the soil. Walnut leaves can be composted because the toxin breaks down when exposed to air, water and bacteria. The toxic effect can be degraded in two to four weeks. In soil, breakdown may take up to two months. Black walnut leaves may be composted separately, and the finished compost tested for toxicity by planting tomato seedlings in it. Sawdust mulch, fresh sawdust or chips from street trees prunings are not suggested for plants sensitive to juglone, such as blueberry. However, composting of bark for a minimum of six months provides a safe mulch even for plants sensitive to juglone." [Ohio]

To be on the safe side, composted material containing juglone should be allowed to breakdown over a period of time before use. This composted material can be used with plants that are not susceptible to juglone damage. If it is important to use it for general composting purposes, testing it first with a few tomato plants for a few weeks should reveal its level of toxicity."

Here are a few more links:

The Walnut Tree: Allelopathic Effects and Tolerant Plants from the Virginia Cooperative Extension.

Black Walnut Toxicity to Plants, Humans and Horses from Ohio State University Extension.

Season All Season
Date 2008-03-27
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According to Ann Lovejoy's October 16, 2003 column from the Seattle PI, a strong ammonia smell indicates "immature" compost that could harm plant roots.

Compost facilities sometimes have bad batches with too much nitrogen in the original mixture of clippings, compared to the amount of carbon, and it can be solved over time by adding "carbon-rich materials such as leaves or [finely ground] wood chips," according to a compost odor factsheet produced by Resource Recycling Systems, Incorporated. Acidity can also be a factor--less acidic mixtures sometimes remain immature until more acidic ingredients (such as leaves or needles) are added.

If you haven't already contacted the company, you might try that. At least one local company stands by its compost with a satisfaction guarantee, and that fact may encourage whoever sold you this compost to make things right for you.

Season All Season
Date 2008-05-10
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Adding sand to clay soil is not recommended as a way of lightening the soil, as it "may create a concrete-like structure", according to the booklet Ecologically Sound Lawn Care for the Pacific Northwest by David K. McDonald. Linda Chalker-Scott addresses the reasons for this in depth in "The Myth of Soil Amendments Part II".

Instead of adding sand, David McDonald recommends trying to till in compost. At least two inches of compost tilled into the upper six to eight inches of soil is recommended, but four inches tilled into the upper twelve inches is preferable . Try to avoid doing this when the soil is waterlogged, as it may damage the soil structure.

Composting the horse manure and shavings you have access to could be a feasible way to obtain the compost to till into the soil. Whatcom County's WSU extension has an extensive discussion of how to compost and use horse manure.They recommend curing such compost at least a few weeks before application, and suggest that one to three months is a good, typical composting time in summer or three to six months in winter.

Alternatively, according to David McDonald, if there are a few months of warm weather between autumn and seeding time, you could simply till the fall leaves and grass clippings into your soil. Depending on your planned schedule, this could be very easy. (You can find McDonald's full booklet "Ecologically Sound Lawn Care for the Pacific Northwest: Findings from the Scientific Literature and Recommendations from Turf Professionals" online as a very large PDF.)

Another option might be to consider some sort of groundcover if you discover that establishing a lawn is an excessively extensive project. Carex species or possibly Juncus phaeocephalus phaeocephalus are more naturally adapted to heavy soils in wet areas than lawn grasses and so may be less work in the end. Though they would not be appropriate for a heavy traffic area, they would be grasslike in structure. Sagina subulata might be more amenable to heavy traffic.

Season All Season
Date 2008-05-14
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It sounds like screening your compost was a good place to start; Mike McGrath recommends removing the "odd original ingredient" from compost this way in his Book of Compost (New York, NY : Sterling Pub. Co., 2006). Woody material should definitely be removed, he says. If your compost does not seem otherwise 'off' (an ammonia smell, a sulfurous smell, very odd color), sieving off the woody material is often sufficient.

Twigs compost more slowly than other material, and you could, if you like, simply re-compost them, according to the King County Solid Waste Division.

There is some debate over the effects of inadequately decomposed material such as your woody twigs in compost and mulch. Linda Chalker-Scott addresses the question of less-than-fully composted yard waste in her May 2003 myth. She agrees that inadequately decomposed yard waste has a reputation of removing nitrogen from the soil, but writes that the way the yard waste is used affects the way it interacts with the soil. As a mulch (a layer over the soil to prevent weeds or retain moisture), it does not significantly reduce soil nitrogen, but as a compost (incorporated into the soil), it may reduce nitrogen in the soil.

If you are still concerned about the quality of your compost, Stu Campbell suggests using the following techniques on municipal compost in his Mulch It! (Pownal, Vt. : Storey Books, 2001) First, test the pH, and, if it is off, store and turn the compost for several months before using it. Mature compost should have a pH between 6 and 8, which you can test using a soil test kit or some of the other options listed on this web page.

Season All Season
Date 2008-06-04
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