Lauterbach: Put life back into your soil

Special to The Idaho StatesmanMarch 28, 2014 

Your goal: rich soil.


"My garden is so crappy I don't even know what question to ask."

What can you do when your garden is a barren waste where soil is so hard weeds struggle to live?

In recent years, developers working on slim profit margins have skimmed topsoil from properties they then build upon, leaving impermeable subsoil as "topsoil." They can then sell the topsoil, raising profit to an acceptable level.

One clue that this has happened to your property is poor drainage. Dig a hole and fill it with water. If it's still full of water by the following day, that poor drainage will doom your gardening attempts.

Other problematic ground is that in which subsoil life has died due to compaction and/or toxic substances applied.

Give that piece of earth a makeover. Put life back into it.

First, check the depth of your soil with a stout wire. If you're in the vicinity of Maple Grove and Amity roads, your soil is probably very shallow, with basalt (lava) hardpan. The depth at which caliche lies as a concrete-like hardpan varies in different parts of the Treasure Valley, mainly south of the Boise river. If you run into hardpan of any type in just a few inches (less than a foot), turn to raised beds or containers.

If you are in another part of the Valley, start by either hoeing or sliding a shovel to shear weeds from their roots. See if you can get your hands on a broadfork (also called a U-bar digger). This is a tined fork wider and longer than those on a spading fork, with two handles set about 18 inches apart. You may be able to rent one, buy one locally or obtain one from Bountiful Gardens, Johnny's Selected Seeds or Lee Valley Tools.

This tool has two long, strong handles, so you can rock the digger back and forth after using your foot to push tines into soil, relieving compaction and aerating the soil. If you can't find one, try rocking a spading fork in your soil.

Your compacted soil probably is mostly clay. Do NOT put sand on it to lighten it. The wrong proportion will yield concrete-like soil. You may put a thin layer of gypsum on it to ease the grip of clay.

Then you can either plant a beneficial cover crop such as buckwheat, an annual rye, or one of the clovers, or let it lie fallow, covered with a friendly substance such as shredded leaves from last year, homemade compost, mushroom compost, or shredded tree trimmings such as those sold by Boise's community forestry division (make a reservation at 384-4083; a pickup load is $15 per yard, and a trash bag is $3). If weeds poke through, pull or hoe them out.

Do not apply synthetic chemicals to this bed. If you must use a fertilizer to get a cover crop going, use a fertilizer identified on the bag or bottle as an organic fertilizer.

The object here is to encourage resumption of life in the soil. Healthy soil should contain millions of microbes and several meters of beneficial fungi in just a teaspoonful of soil, in addition to earthworms and other visible creatures. If you've been using synthetic chemical fertilizers, they may be responsible for the death of some of those micro-organisms, perhaps those critical to soil health.

Let the soil rest for an entire growing season, hand-pulling or skimming weeds from the surface. After leaves fall, cover the area with shredded leaves and, if available, lawn clippings that haven't been sprayed with herbicide. You could add a layer of homemade compost, too, building a "lasagna garden."

You could plant into that layered mix by spring, or if you want to raise plants that have deeper roots, test the soil under the layers with a spading fork. If soil isn't lighter and more crumbly by spring, build raised beds and fill them with topsoil purchased from reputable garden centers and organic matter clean of herbicide contamination.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.

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