Good organic soil is available at your garden center, but if you are planting more than just a small bed, you may want to make your own. Your own soil will be soft and crumbly, filled with good organic nutrients, and teaming with earthworms.
Good soil is comprised of approximately 25% minerals, 25% water, 25% air, and 25% organic matter, both decomposed and live.
The minerals are in the form of fine particles of rock, weathered and ground by earth movements over the eons. The particles may be large (sand), medium (silt), or small (clay).
Air is needed by living organisms and plant roots in the soil. It contains atmospheric nitrogen which some organisms, attached to plant roots, fix into the soil.. Air keeps the soil light and non-compacted.
Water is held between soil particles and is absorbed by plant roots and is used by the soil organisms.
Organic matter in the soil is decomposed soil organisms and plant material. It retains moisture, adds nutrients to the soil for living plant use, and is food for the living soil organisms.
The soil life is in the form of bacteria, fungi, earthworms and other tiny creatures that convert organic matter into food for plants.
Bags of top soil are available at your garden center for less money than potting soil, or if you need a lot you can buy it by the truckload. Just don't assume that all topsoil comes ready to plant.
Do a hand test of the soil that you plan to use. Pick up a hand full and squeeze it into a ball. If it sifts through your fingers, a little or a lot, you have sand. If it forms a slick, dense ball, it is clay. If it crumbles into light clumps, it is just about right for planting.
Whether you have sand or clay you use the same process to make it into organic soil, Add mulch and compost to add body to the sandy soil and to add air pockets the the clay. Even if you soil seems friable, go ahead and enhance it with compost and mulch.
High carbon brown mulch includes fallen leaves, straw bales, wood fibers from newspapers and cardboard. All these materials need to be finely shredded. Chop the leaves with the lawnmower. Shred the straw bale and run the lawnmower over it. It is best not to use hay bales as they may contain seeds that will come up in your garden. Newspapers and cardboard can be put in the compost bin to decompose.
Add nitrogen rich green grass clippings from your lawn, assuming you do not have weeds growing there. Add seasoned manure, chicken or horse, which may be free to you from people who keep those animals. Add kitchen compost, peat moss, and earthworms, if you have a source.
A hand full or two of bone meal will add phosphorus and and protein to your soil.
Before you put your garden space to bed each fall, you should feed it again from your compost pile or bin. Add a little bone meal and cover the beds with shredded leaves or straw. Dig them in when spring comes.
Enjoy your wonderful organic vegetables grown in your own organic soil!
Image is from: http://www.rodalesorganiclife.com/garden/disease-defense