There isn't a perfect soil. At least not one soil for all plants. Different plants need different types of soil. So before you spend lots of money amending the soil it is necessary to decide what plants you want in that area. We've all seen as we walk through the garden center the different soils. Garden soil, Potting soil. Cactus soil, African Violet soil each specially mixed for a certain type of plant. So the place to start is with the plant. For an example lets take tomatoes.
Tomatoes are so hardy that if they didn't give us fruit they would probably be considered a weed. But to get the maximum good fruit they need conditions that helps them produce the best crop.
So when I research tomato requirements what do I find out?
They are heavy feeders,
The fruit is suceptable to BER,
They like full sun,
the ground needs to drain well.
They are in the same family with squash and can take on the flavor of squash if planted to close to it. [Not a good thing].
Tomato plants won't grow stabilizing roots if they don't experience wind when they are young.
There are determinate and indeterminate types of tomatoes.
Tomatoes can grow roots all along their stem.
Tomatoes are suceptable to soil borne diseases.
Tomatoes grow suckers in the joints of their branches these suck the engergy from the tomato and do not produce fruit.
The plants need regular deep waterings that can be decreased while the fruit is ripening.
Now that you know all of this what do you do about it? Try the following.
How to respond to a discription like:
Heavy Feeder - Before planting add 50% compost to your ordinary garden soil. Compost is normally pH balanced but do a soil test after mixing it in well so you know what other amendments you might need.
BER suceptible - This means that I will probably want to have a soil test sent to the local University Cooperation Extention. They will give much better results than the 10.00 tests you can by at the local garden center. It will include all the trace minerals that a plant may need. Ber is caused by a lack of calcium that can be caused by improperly amended soil or improper watering techniques or improper pruning techniques. Wow bunch of stuff can decrease a crop huh? For me I added calcium by powdering egg shells in my coffee grinder and then lightly sprinkling it over my flower beds before I tilled the soil. The University Coops are the place to find the rations for adding amendments to soil. There website can be a wealth of information along this line.
Full Sun - Tomatoes like heat and light this isn't a soil thing but it does affect the soil in what kind of mulch you use on top of the soil. In this case the black plastic sheets are a good thing since they will keep the soil hot as well as moist. But it can't be applied until the tomatoes have some size to them or they would fry the seedlings.
Drain Well - Sand is an intragral part of dirt. How much is there will determine in part how well the soil will drain. If your garden soil is mostly bio-matter you may want to add sand. If your garden soil is mostly clay you do not want to add sand because you'll just cause it to immitate concrete. Not a good thing. How much sand is enough? Again that depends on your plant choice. What I want is for their not to be any standing water where my tomatoes are going after it has rained. The dictionary quoted a ratio of equal measures of clay, sand and bio-matter. But of course it depends on your plant.
Squash and tomatoes - Friends and Foes in the Garden [Or what is commonly known as companion planting]. Some plants make good friends to other plants and some don't. For example basil can keep pests away from tomatoes, onions can make tomatoes taste better and squash can make tomatoes taste terrible. So what you plant in the soil next to your tomatoes is also very important.
Some plants like peonies will be noted with information like they need to be placed in protected areas. The exact opposite is true of tomatoes. Naturally a vine like plant in order to get it to stand upright even alittle you need to expose it to wind. Usually this is a fan if you grow them from seed indoors.
Determinate/Indeterminate - this has to do with their height and how they set fruit. Determinate will set fruit all at once and will have a more upright growth pattern. Indetermine is more viney and will produce fruit all season long. Since tomatoes require good air circulation all around them this information is very important when spacing the tomatoes apart. If they are to close together it will inhibit their growth especially when small.
Now how deep to plant into the soil - This is a very important question with all plants. To deep and they may not come up at all or they may not bloom. To shallow and they may fall over and die. For the tomato it is necessary to know that they can grow roots all along their stem. So with them you want to bury them at least up to their first set of true leaves. If you don't want to dig a hole that deep you can trench them. They will right themselves in short order and begin growing sunward.
Soil borne Diseases - What this means for the soil is that crop rotation is important, Also Mulching is important, and for the tomato when it is 3 feet tall it is possible to prune off the bottom of foot of leaves from off the plant to stop the fungus from being able to invade the plant through the leaves.
These don't have anything to do with soil but since we are using tomatoes as an example i'll add this information here.
Tomatoes grow sucker branches at the joint of their branches. These stick out at a 45 degree angle and will not produce fruit. They should be pinched off.
Deep regular watering is necessary to prevent BER and spliting but the amount of water should be lessened as the fruit begins to ripen this will cause the fruit to be sweeter.
Now I guess you need another plants requirements to see the differences right? Well I'll add that later. this was a lot of work.