Green Gardening: Web site helps you turn dirt into topsoil

I often am asked by discouraged gardeners why our Northwest soils are so hard to work with when a huge range of native plants flourish here. While undisturbed native soils are constantly replenished by falling leaves, many garden sites are not just disturbed but scraped down to hardpan. It's very hard to garden on subsoil.

That's why new home sites can be especially disappointing for gardeners. When poor quality artificial topsoil is thinly layered over impenetrable subsoil, a young garden is usually doomed. Lawns often fail within a year or two, and few plants survive, let alone thrive.

Happily, a new program aims to educate Puget Sound builders about the proper handling of soil during the building and remodeling process. If you are building or planning a new home, send your contractor the link to a Web site developed by the Washington Organic Recycling Council.

This easy-to-navigate site -- buildingsoil.org -- shows builders and homeowners how to apply "best management practices" whenever a home site is developed. Rather than removing the topsoil, builders are encouraged to retain and protect existing topsoil. Native plants, often removed as "trash," should be marked for preservation and protection.

The Web site offers practical ideas, techniques and management practices that also will benefit homeowners doing their own contracting. You'll find accurate, clearly expressed information on how to repair poor and compacted soils, amend commercial topsoil and use compost to heal damaged soils.

There also is great information on implementing soil-handling practices now required by Washington state's storm-water permitting process. These state-mandated practices are rapidly being adopted by most Western Washington municipalities and counties to help protect water quality and improve life for endangered salmon species.

Happily, good soil-handling practices are practical, easily carried out, and hugely beneficial to both gardeners and fish. Improving soil aeration, tilth, and humus content makes both plants and salmon happy. Good soil preparation also makes gardening much easier and vastly more rewarding.

If you are gardening on a home site developed since the 1950s, especially in planned communities, your native topsoil very likely was removed. The good news is that it's never too late to amend poor soil.

If you are making new beds, take time to loosen the existing soil as deeply as you can before bringing in topsoil or compost. Use a long-tined fork to open up soil in small areas. For larger areas, till as deeply as possible. While tilling is not a preferred practice these days, it is still a valuable way to increase soil aeration.

With heavy clay soils, it is critical to use topsoil that includes a significant amount of compost. Only humus can really modify heavy clay, so heaping cheap topsoil over subsoil will not be a lastingly successful fix. Cedar Grove's Veggie Mix is an excellent example of well-made topsoil that isn't too sandy and retains its goodness for many years.

When a garden already is fully planted, it doesn't make sense to try to double-dig or loosen soil to a depth of a foot or more. However, annual mulching with humus-rich compost and aged manures will gradually do the job for you. As compost reintroduces lively soil biota, worms and other soil aerators will slowly turn dreadful dirt into sumptuous soil.

When compost is hard to handle, a good commercial product can help open heavy soils. A few years ago, my husband sprayed a section of the yard with a probiotic substance called Lazy Man Liquid Aerator. We haven't developed that part of the garden, so I forgot all about it. This winter, when wild rains brought the water table up to unprecedented levels, that section drained quickly while surrounding lawn stayed soggy.

The liquid aerator is available locally for about $35 a quart, enough to cover about a quarter of an acre. To find out more or order online, visit the company Web site at outsidepride.com.

As your soil improves, you'll notice less runoff after heavy rains. That's because soil rich in humus absorbs many times more water than compacted soils. Plant roots also thrive in well-aerated soils, and healthy root systems are the key to sustainable gardening.

As your plants gain great roots, they'll need less water, less fertilizer and less pest intervention. What could be better for garden and gardener alike, not to mention those stressed-out salmon?