Garden Variety: The dirt on dirt

I was so excited about moving to Lawrence some 20 years ago.

The house was great and the lot had really great open spaces and sun exposure. Bringing out my tried and trusted tiller, I began. The tiller worked really well. It easily skipped over rocks, sparked on the flint and effortlessly scraped up good old brown clay. Sound familiar? Welcome to Lawrence.

As I’ve discussed in previous columns, plants need air, water and nutrients. Soil just happens to be the carrier we use to bring these requirements to the roots. Ideally, soil should contain 50 percent mineral matter, 25 percent air and 25 percent water. This perfect mix is seldom found.

Ideally, soil should contain 50 percent mineral matter, 25 percent air, and 25 percent water. This perfect mix is seldom found.

Clay soil holds way too much water for too long. Plants suffer and appear to be dehydrated (when they are actually drowning) so we water, just the opposite of their need. On the other side of the spectrum, sandy soils hold almost no water and the plants look dehydrated. All the water we apply just soaks past the roots with little or no benefit. So, if I add sand to clay soils, or vice versa, I should end up with a very happy compromise, right? No. I simply end up with concrete.

Getting the perfect mix 50-25-25 is best accomplished with compost. By compost, I mean any plant material, including shredded leaves, grass clippings, homemade compost, city compost, purchased compost, etc. Compost is basically organic material that decomposes easily in the soil or has previously been decomposed. Application over the top of the soil will work as the ground freezes/thaws, wets/dries, and the worms or arthropods pull it under the surface. Better results are obtained if the plant material can be dug into the soil, as in the use of the above-mentioned tiller.

Compost is not a cure-all. There are still the chemical aspects to consider. Plants need three major minerals to grow well: Nitrogen, potassium and phosphorous. Other elements are also needed, but usually in small portions, and are almost always available. Potassium and phosphorus are readily found in our soils, so the most common nitrogen is our concern. Compost can supply some of this, but usually not in an immediately available form. Timing and amount of added nitrogen depends on the crop to be grown and the last application.

The acidity or alkalinity — the pH — of the soil is also of serious importance. Some plants like an acidic soil; others are base-oriented. A neutral pH suits most plants just fine. There are a few reliable home soil tests available, but your best bet remains a soil test through an Extension office.

Twenty years of removing rocks and adding compost have almost made the tiller obsolete. Good soil is friable and easily worked. Building and maintaining the soil is the very best addition to any garden.