How to Improve Your Garden's Soil

The basics on soil and how to turn dirt into a fertile garden growing place, including: nutrients, fertilizers, soil tests.

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    Author Gail Damerow gives her plants a boost with an application of natural fertilizer. You can easily turn mere dirt into fertile garden loam.

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I thought I knew a lot about garden soil until I moved to my present home and tried to plant my first garden there. I wandered out with a shovel to turn the soil for spring planting, and ended up scurrying for a pick-ax to break up the hard-packed clay. It was a far cry from my previous garden, which had such beautiful loamy soil that I could (and often did) harvest potatoes simply by rooting for them with my hands.

Obviously, I needed to know more about the relationship between clay and loam before I could turn the former into the latter.

Garden Loam

The first thing I learned is that clay is one of three basic soil types, the other two being sand and silt. All three are made up of rock particles. Clay, as I learned the hard way, consists of fine particles that turn brick hard when dry and that cling to a shovel when wet. Sand, I knew from my years living in the Arizona desert, is coarse, gritty, and porous, whether dry or wet. Silt lies halfway between clay and sand. When wet, it sticks together but doesn't stick to a shovel.

Loam (aha!) contains a mixture of clay, sand, silt, and humus. Since clay, sand, and silt are made up of rock minerals, they comprise the inorganic component of loam. Humus, by contrast, is decomposed plant matter and is therefore the organic component. Good garden loam contains at least S% humus, and humus improves sandy soil by increasing its ability to absorb and retain moisture. It also improves clay soil by loosening it, making the soil easier to work, and preventing surface crusting so that sprouting plants don't have to struggle so hard to pop through. This is just what my clay soil needed.

An obvious source of humus is used barn bedding, worked directly into the soil. But it was spring and I was ready to plant. I didn't have time to wait for "hot" manure to decompose. Fall is the time to work manure-soaked bedding into the soil, in anticipation of spring planting. Another obvious source of humus is compost, but I had just moved and didn't yet have a compost pile. I remedied that right away by nailing some planks into a series of four-foot-square corrals and tossing in all the kitchen scraps, grass clippings, and other organic matter I could get my hands on. Kept slightly moist and aerated by occasional turning, the "pile" would one day provide all the compost my garden needed.

Like any other source of humus, compost improves soil texture and makes the soil easier to work. Compost also adds nutrients and encourages the growth of beneficial soil-borne microorganisms that dissolve those nutrients, so they can be readily absorbed by plant roots. But my compost pile was growing slowly and decomposing even more slowly. I needed lots of humus in a hurry. So I called a local saw mill and had them deliver several truckloads of well rotted sawdust to till into my garden. Voila! I had loam. But it wasn't yet fertile loam.

Plant Nutrients

Clay, sand, silt, and humus all contribute certain nutrients that plants need in order to grow and thrive. Just what kind of nutrients loam contains, and how much of each, depends on three things: the sources of the mineral and organic matter making up the soil, the degree to which the soil has been weathered and eroded, and the amount of nutrients used up by plants previously grown in the soil.



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