Soil Basics for Urban Gardeners

Unless you’re using hydroponics for your urban garden, the most important thing you can do to insure healthy plants is to have healthy soil.

Soil Composition
Soil is often divided into various categories, such as clay, sand, silt, and loam, although there are an infinite number of soil varieties because soil compositions can vary widely in organic matter, large and small rocks, minerals, pH, and other factors. Most gardeners consider soil that has a combination of sand, silt, clay, and organic matter to be good soil.

pH and Urban Gardening
pH is a scale used to measure the concentration of hydrogen ions in a solution. The pH scale ranges from 0 to 14. Acidic substances have smaller pH numbers and more hydrogen ions. Alkaline substances have larger pH numbers and fewer hydrogen ions. 0 is extremely acid; 7 is neutral; and 14 is extremely alkaline. Limestone is an example of a very alkaline mineral. Sulfur is an example of a very acidic mineral. Note that arid regions tend to have alkaline soils and regions with heavy rainfall tend to have acidic soils.

Whether you’re using a commercial potting soil, or you are fortunate enough to have a little garden plot at home for planting, measuring the pH of your soil is a good indicator of how your plants will perform. Different kinds of plants thrive in soil with different levels of pH. You can test the pH of your soil with a simple pH testing kit. A good quality pH test kit is worth the extra expense because inexpensive ones are often inaccurate. Testing the pH will also help you determine if you need to make changes to the soil composition. Once you know your soil’s pH, ask your local nursery if your soil is suitable for the plants you’d like to grow. You may need to work your soil a little to reach the desired pH level. (See below for more information.)

Testing Your Soil

Here is a terrific little electronic soil testing tool that can tell you how your soil is doing quickly and easily. Another good way to test your soil is with the “Ribbon Test.” After you take a soil sample, roll it back and forth in your hand. If it sticks together easily, it is high in clay, if it simply falls apart, it is probably has a lot of sand. Clay soils don’t drain well and are difficult for the roots to penetrate. Sandy soils drain well but don’t retain nutrients. Adding organic material will help both sandy and clay soils.

The most accurate way to test the overall health of your soil is with a Garden Soil Testing Kit. These kits are relatively inexpensive and come in various styles. You can even buy an electronic soil tester that will test the pH, as well as fertility, how much light you are getting, and other aspects for effective urban gardening.

The Magic of Compost
Adding compost can work wonders if your soil is out of the ideal pH range. Adding compost will also improve soil that is too sandy, has too much clay, or is low in the organic material that plants need to thrive. Composting is also a wonderful way to reduce waste in your home by making use of kitchen scraps, garden waste, and other green material. If you don’t know much about composting, don’t worry. You can find more information on composting at the Compost Guide.

Soil drainage is also critical to plant health. Mixing in compost is the best way to improve drainage. You can also try digging out a good quantity of the soil, around 16 inches deep, and placing a layer of fine gravel at the bottom.

Another great site about composting for the urban gardener is provided by the Brooklyn Botanic Garden.

Mulching is nature’s way of composting. Mulching helps to keep weeds from growing and facilitates moisture retention in the soil. Mulching also begins the process of natural composting. Between treatments, soil organisms help to decompose the mulch that is closest to the ground. Earthworms and other critters that live in the soil pull composted material into the ground and naturally feed your plant’s roots.

You should add a little mulch each year to your garden to keep the process going. You can use mulch even when your soil is in good shape. The mulch will keep the soil healthy and productive. You can further support your soil by adding a dose of organic fertilizer. Your mulch will work best when you add this natural fertilizer over the entire garden bed so that the whole area will gradually become healthier.

For moreinformation on mulching you can go here.

Want to learn more about Soil Basics for Urban Gardeners?  is an excellent resource for learning about the types of soil and how best to prepare it to get the most of your garden. It comes with a comprehensive list of links on the best soil for any variety of plant you are planning to grow, and includes tips for beginners and experienced gardeners alike.

Urban Garden Magazine  tells you everything you need to know about vermicomposting in this informative article. It explores the link between earthworms and the health and potency of your soil. Vermicomposting has been shown to significantly improve the quality of your soil while adding to the health and vitality of your plants.

You can check out this article from Cornell University to get you started in learning about soil. It tells you how to evaluate the suitability of your soil by examining it’s color and texture. It also explains the importance and purpose of basic soil acidity tests.

This online blog  about container gardening has some good information about fertilizing your soil. It tells you which three nutrients are of prime importance for your growing plants and how to adjust your fertilizers to properly condition your garden for the kind of plants you want to grow.

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