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Garden Soil Preparation

by chuck.mcmullan

Before you begin sowing seeds or buying plants, you need to prepare your soil and make sure it’s in good condition for the growing season. For your vegetables to thrive, they need a well-prepared garden that will provide them with all the necessary food, water, and support from the very beginning.

Understanding how the soil provides for plants will enable you to decide what you need to do: whether or not you need to dig, what you can add to your soil to improve it, and whether it needs lime or additional fertilizers. Get this right, and you’ll have a successful harvest.

Soil Management

Good soil management is key to any garden. No matter how poor the soil may be at the start, proper management will gradually create a productive soil. Soil is comprised of four main ingredients – minerals, organic matter, water, and air. In the average soil, the mineral component is about 50% of the volume, air, and water about 20-25%, and organic content is as low as 5%. Notice that nearly half of the soil is “space,” which is occupied by water and air. These spaces are also filled with the soil’s thriving populations of plants and animals which break down plant and animal residue into organic matter or humus. The worms and insects initiate the physical breakdown, while the microscopic bacteria and fungi complete the decomposition process, releasing nutrients as a by-product.

The ideal soil is crumbly, well-aerated, porous material that holds moisture and yet drains well, and is nutritious for plant growth. The way to improve the soil structure is to rearrange the particles. Organic matter is the tool. To review briefly, soil particles come in three sizes: clay (small), silt (medium), and sand (large). The function of the largest particles is chiefly as a framework for the smaller ones; they merely keep the soil porous. Clay and organic matter are the soils charged particles utilized for ion exchange. If the soil is sandy, the addition of generous quantities of organic matter will fill in the framework of sandy soils, to give water molecules something to hang on to. If the soil is heavy clay, again, the addition of generous quantities of organic matter provides the glue to aggregate the minute clay particles into larger particles. The larger the particles, the bigger the pore spaces, and the better the soil aeration. Organic material is your friend when trying to improve your soil conditions. You may want to consider making a compost pile so you can use your biodegradable wastes to make food for your garden.

Identifying Your Soil

The best garden soil is loam, made up of a mixture of sand, silt, and clay. A quick and easy test to determine your type of soil:

  • Moisten a pinch of soil and rub it between your thumb and index finger. Sandy soil feels gritty, silty soil feels slippery, and clay soil feels sticky.
  • Try molding a handful of moist soil into a ball. If it falls apart, it’s sandy; if it molds easily into a ball, it contains a lot of clay. If you can give the ball of soil a polish with your thumb, there’s an even higher proportion of clay.
  • You could also try mixing some of your soil in a clear drink bottle and then shake it up. Set in on the table and wait for everything to settle. The sediment will eventually settle in layers, and you can determine the proportions of silt, clay, and organic matter in the soil.

Sandy soil is quick to warm up in spring, is light and easy to manage, and is rarely waterlogged. However, it is a hungry, thirsty soil because water and dissolved nutrients drain through it before plants can use them. A heavy clay soil remains cold for longer in spring, and it is difficult to dig. It soon becomes waterlogged and airless in wet weather, yet it can bake rock hard in droughts. However, clay soil usually contains adequate quantities of vital plant nutrients.


While plants make their food with the energy from sunlight, they need nutrients to make this happen. When dissolved in soil moisture, these nutrients are taken up by the roots. There are three major nutrients, nitrogen, phosphorous, and potassium – often abbreviated with their chemical symbols of N, P, and K. In general, nitrogen helps with leafy growth, phosphorous helps provide root development, and potassium encourages fruit and flowers. Other mineral nutrients needed in smaller quantities are calcium, sulfur, and magnesium, plus trace elements, which include iron, boron, copper, manganese, molybdenum, and zinc.

Vegetable pH Preferences

Most vegetables prefer soil between 6.5 and 7.0, but the following types will tolerate soil with higher levels of acid (below 6.0) or alkaline (above 7.0)

Acid Tolerant PlantsAlkaline Tolerant PlantsAlkaline and Acid Tolerant Plants
Carrot (5.5 - 6.8)Asparagus (6.5 - 7.5)Celery
Celery (5.5 - 7.5)Beet (6.5 - 7.5)Garlic
Eggplant (5.5 - 6.8)Brussels sprout (6.0 - 7.5)
Endive (5.5 - 7.0)Cauliflower (6.0 - 7.5)
Garlic (5.5 - 7.5)Celery (5.5 - 7.5)
Potato (5.8 - 6.5)Cucumber (6.0 - 7.5)
Radish (5.5 - 6.5)Garlic (5.5 - 7.5)
Rhubarb (5.0 - 6.8)Leek (6.0 - 7.5)
Sweet potato (5.5 - 6.5)Melon (6.0 - 7.5)
Watermelon (5.5 - 7.0)Okra (6.8 - 7.5)
Onion (6.0 - 7.5)
Shallot (6.5 - 7.5)

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