Growing Concerns 247: Improving clay soil on a bare bones budget

I am a prisoner at the Mound Correctional Facility and am currently endeavoring to convince the administration to begin a gardening program. I have a problem, namely clay soil and lots of it.

Many of us have tried various remedies -- "stealing" wood chips from underneath bushes, adding sand from the softball diamond, etc. -- all with little or no effect. I would water in late afternoon or early evening to try to aerate the soil when it was moist, but it still seemed to give way to damage and subsequent stunting of plant growth, especially in my pepper plants.

I was wondering if you have any suggestions. The solution would have to deal with readily accessible items (grass clippings, water, wood chips, sand, etc.). If these won't help, perhaps the administration might be talked into purchasing something to combat this problem in an effective manner.

Also, I was wondering about plant food. I'm trying to stay away from chemicals, if possible. Any ideas? - M.Q.

Clot the clay!

Clay particles are tiny, platelike rock fragments. They stack on one other, fitting so tightly that air and water can't flow between them. The crushing weight of grading machines and foot traffic can compound this natural tightness. Since roots need oxygen and rot where water can't drain, plants struggle in clay.

Solutions lie in sticking rather than stacking -- adding ingredients to make clay "clot" into looser, ball-like crumbs. Coarse sand sounds good for lightening clay, but it's not a "sticker." Sand grains are spherical bits of weathered rock that rest loosely on each other and leave plenty of room for water and soil -- an improvement in soil crumbs but not the essential ingredient. Humus is the key -- organic matter residue that glues clay to clay and clay to sand in crumbs that preserve air space, offer up nutrients and hold some water, yet allow excess water to fall quickly out of pore spaces.

Problem may lie in compaction more than soil type

We deal often with compacted clay -- it's what building processes create around most new homes. We don't rototill there, since that can pulverize what few crumbs do exist and make the whole mix sift down even tighter. Tines also press down hard at the bottom of their rotation, glazing subsoil to a ceramic consistency. If anything drains more slowly than compacted clay, it's clay over impervious hardpan.

So we break clay into large chunks, using a spading fork -- a tool like a pitchfork with broad tines. We cover that blocky, uneven surface with organic matter three to four inches deep and fork it over again. Compost is best for this step, but anything organic can work. In a Rodale Institute study, shredded newspaper was worked in with good results.

We use a bow rake to smooth the bed just enough to plant. If that's too coarse for viewing pleasure, we cover the lumpiness with two inches of that great leveler, mulch. We want the clay to remain chunky, surrounded by air-filled, well drained organic matter. Frost, water movement, and the passage of worms and other soil dwellers will erode the clay and blend it with the humus.

 This requires plenty of compost -- one cubic yard, or 27 one-cubic-foot bags, cover 100 square feet three inches deep. If you can't get so much, do what gardeners do best -- create your own organic matter. By growing cover crops and turning them under, you can convert soil minerals into organic matter.

Cover crop: Just add seed

If you can make the soil evenly marginally plantable, sow oats, buckwheat, or hairy vetch this May. Three ounces of oats or buckwheat, or one-and-a-half ounces of hairy vetch will seed 100 square feet of bed. Turn under oats or buckwheat before they go to seed, then sow a second crop which will die back during winter as a natural mulch. Hairy vetch can grow for a year before being turned under. Year by year, this improves the soil structure.

Growing a legume such as hairy vetch may also be your fertilizer answer, taking nitrogen from the air and putting it into the soil. Legumes grow in symbiosis with root-dwelling bacteria which can absorb atmospheric nitrogen unavailable to most plants -- this nitrogen is "given" to the host plant. Plowing under legumes can supply enough nitrogen to grow a respectable 72 bushels of corn per acre without additional fertilizer.

You can even "intercrop" cover crops and vegetables. Sow hairy vetch around a wide-ranging plant such as squash as it begins to spread in early summer. Let the two grow together to reap both vegetables and soil-improving organic matter.

For more on cover cropping, contact your County Extension Office and ask for a list of  bulletins on this subject, yours for a small fee. One bulletin author at our local extension office helped us decide which cover crops to recommend to you. He's studying the use of cover crops to trap excess fertilizer in agricultural fields, converting potential groundwater pollutants into organic matter -- nutrients "in the bank." Along the way, he's quantifying cover crops' other benefits, such as buckwheat's attraction of beneficial insects -- natural predators of pest insects -- and the herbicide reduction possible when cover crops are grown as a weed-suppressing mulch.

You can buy oats, hairy vetch and other cover crop seed at feed stores in your local area.