Improving soil with soil amendments

Substances that you mix into soil to improve its texture and overall hospitality to plant roots are called soil amendments.  Follow these guidelines to learn more about how to improve the quality of your soil.

Improving soil with soil amendments

1. Compost

The most useful and versatile soil amendment is compost, which is made by mixing together various organic materials, such as kitchen vegetable scraps, lawn clippings, and dried leaves, so that they decompose within a few months into a dark, crumbly material that is also called humus.

Mixing compost into soil enhances the soil's ability to retain both water and air, and provides it with a crumbly texture that roots can easily penetrate. In addition, compost contains enzymes and micronutrients that benefit plants by boosting their immune system. The neutralizing effect that compost has on soil pH helps plant roots absorb nutrients from the soil.

Compost should not be considered a fertilizer, because compost usually contains only a little nitrogen, the nutrient most needed by growing plants, and the nutrient that is abundant in most fertilizers.

You can make your own compost by piling together plant debris, soil, grass clippings, shredded leaves, and vegetable materials, and then adding enough water to keep the mass moderately moist. Turning the pile speeds the decomposition process, which is always faster in warm weather, and probably stops entirely in winter. And while composting is a convenient way to recycle garden refuse, if you are planting numerous plants you will probably need to buy extra compost.

Compost is sold in bags at garden supply stores, or you can buy it by the truckload from farmers who turn out batches made from sources ranging from rotten hay and stable litter to spent mushroomgrowing medium. And, many towns and cities now compost yard waste and make the material available to residents at a very reasonable cost. Because compost is so variable in content and nutrients, it is often wise to buy a small amount from any given source, try it, and then decide if you want more.

2. Acidic amendments

Plants that require acidic soil, such as ferns, azaleas, and rhododendrons, benefit from being mulched and having their planting holes amended with acidifying humus, such as peat moss, pine needles, or oak leaves. Peat moss has the added advantage of being a poor medium for soil-borne fungi, so it is also good to use in situations where root rot is to be avoided at all costs.

For example, a mixture of peat moss and sand makes a good rooting medium for soft-stem cuttings. Leaf mold is nothing more than composted, or rotted leaves. Fully composted leaves will be nearly neutral in pH, but if you use partially decomposed acidic leaves like oak leaves, it will be slightly acidic.

Leaf mold is seldom sold, but it is easily made.

  • Simply pile leaves in a shady place where they will be regularly dampened by rain, and forget about them for two years.
  • That's how long it takes for tree leaves to decompose into a material that, when stirred lightly with a digging fork, breaks apart into dark brown, crumbly leaf mold.
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