Green Gardening: No joke: No-till farming saves topsoil

Many gardeners are frustrated when their hard work does not pay off. The good news is that it probably is not their fault. The hardpan, clay and sandy soils of the maritime Northwest can challenge even advanced gardeners.

If hours of weeding, tilling, watering and feeding have resulted in disappointing yields and frumpy produce, here's more good news: There is an easier and far more rewarding way.

As bio-intensive gardening expert John Jeavons often points out, conventional agriculture and gardening methods waste dreadful amounts of resources, from time and effort spent watering, to fertilizer and topsoil.

Indeed, for every a pound of food in the grocery store, between two and seven pounds of topsoil are lost. Every important waterway in America is polluted with runoff laden with fertilizers and pesticides. A growing oceanic dead zone now stretches from Texas to Florida, thanks to the cornfields of America.

But wait -- there's even more good news! By adopting no-till and bio-intensive practices, gardeners and farmers alike can heal and preserve our precious resources, from soil and water to the air we breathe.

No-till farming and gardening reflects the knowledge that living soil consists of complex colonies of biota, from tiny bacteria and fungi to earthworms and bugs. Instead of removing crop residues from fields or beds, we leave them to compost in place. New crops are planted among the remains of the old, reducing soil and moisture loss and retaining nutrients that help feed the new plants.

Conventional farming and gardening depletes soil by removing nutrients and humus (compost and decaying plant material). Left in place, that humus builds soil tilth and quality, so crops grow better with less fertilizer and water.

The key to all sustainable gardening or farming is excellent root development. To this end, bio-intensive gardening begins with a one-time deep soil loosening, usually to a depth of 2 feet. Since most gardening (and farming) involves disturbed and degraded soil, the subsequent improvements more than make up for the initial disturbance.

Most bio-intensive gardeners use a method called double-digging to loosen the soil. To try it, mark off a 10-by-10-foot bed and use a garden fork to loosen the soil as deep as you can (usually about a foot). Rake out all weeds and roots. If the soil is dry, water it well, then let it stand overnight. Begin by excavating a trench a foot deep and wide, reserving the soil on a tarp. Try to keep the reserved soil as undisturbed as possible (same side up and unmixed).

Loosen the soil at the bottom of the trench to a depth of about a foot (again, if it's dry, wet it thoroughly and let it stand overnight). Now dig a second trench, replacing this removed soil into the first trench. To avoid soil compaction, use a digging board to spread your weight evenly.

Keep moving along, trench by trench, using the reserved soil to fill in the previous one. Rake the soil to make a smooth bed, then mulch with an inch of compost.

Now you can plant anything, from ornamentals to edibles. For comparison, prepare a matching bed by your usual methods and plant the same kinds of things in each bed. Over the next season, keep notes about each bed's performance.

In future seasons, don't till or do more digging than you need to for planting. Just layer on compost and nutrient mulches like soy meal or kelp. If you prefer to remove crop residues, replace them with a blanket of compost to keep your topsoil in place.

Recycle all removed plant waste into compost, either in your backyard or through a curbside recycling program.

Next week we'll look at several ways to keep spent plant material on site without attracting pests or making a big mess.

More information -- growbiointensive.org