The average home garden should have about 20 inches of fertile soil. While the roots of many vegetables are shorter than 12 inches, their rootlets may go down eight feet or more into the subsoil. The deeper the fertile soil, the more productive your garden will be. The yield of vegetables in 20 inches of fertile, aerated soil, can be up to double that of a conventional eight-inch garden depth.
To create the best soil, you must start with double digging. This is a process of digging a trench two shovels deep for the width of your garden and placing the top soil on the bottom of the trench and placing the bottom soil on the top. This puts all the surface weed seeds at the bottom where they are unlikely to germinate and creates a much deeper layer of soil for the roots to grow in, keeping in mind that many vegetable roots go down at least four feet, or more. As you fill the trench, add layers of compost, mixing it into the rest of the soil.
Every year, try to add an inch of compost, incorporating it into the top six inches of your soil. Generally, this provides all the nutrients that plants need to continue to flourish.
Plants need nutrients, water, and air. A soil with lots of compost holds moisture, has pores of oxygen, and generally has all the nutrients needed for healthy plant growth. Without these three components, plants may become stressed and unhealthy. Healthy soil produces tasty, healthy vegetables. Healthy vegetables are good for your health.
The best way to get a 20-inch depth of soil is to put a raised bed on top of five inches of garden soil. Two two-by-eight untreated boards will give you the extra 15 inches. Then complete the double digging by filling the raised bed with the top layer of soil, followed by the bottom layer. If there is too much clay, add some sand. Mix in a generous amount of compost. Make your raised beds are four feet wide to allow for easy weeding, thinning and harvesting. Beside each raised bed there should be a 16-inch walkway, with up to five inches of wood mulch. It is easy to decide where to plant each vegetable, keeping mind the need to rotate your vegetables, not planting the same vegetable in the same area for three years. Each vegetable takes specific elements, such as nitrogen, potassium, calcium, iron, copper, or manganese, etc. Growing the same vegetable in the same area year after year depletes the soil, and the resultant growth is compromised. The application of compost rejuvenates the soil.
Each year add about two inches to the surface and work it into the top six inches.
If possible, make your own compost, or get free compost from the city. My process Is simple and not very time-consuming. I have two large bins of two-by-eight lumber, one smaller than the other. Starting in July, I add all my organic material into the larger bin, adding some dirt every six inches or so, until the next July. Each July, I turn over the contents of the large bin into the smaller one. Then in September, I spread the contents of the smaller bin onto my garden, incorporating it into the top six inches of the raised bed. While not completely decomposed, the undecomposed material is food for the underground web of life as they create humus, the food for the plants.
Vegetables need sunlight, water, and soil to thrive. Of the three, soil and water are the most important. Rainwater is best; it is cheap and relatively uncontaminated. Before planting larger vegetables such tomato, brassica, or squash, I insert large tins (e.g. tomato) with the bottom cut out, at the proper spacing for that vegetable. To water, simply fill each can once or more. The water gets to the roots instead of evaporating from the surface. On hot days, check for wilting leaves; this indicates the plant needs watering.
Charles has written a book based on his experiences – Urban Gardening, Planning to Preserving.
