The foundation upon which nearly all plants grow is soil. Knowledge about the nature and properties of soil will give a better understanding of how to use soil more effectively to support healthy plant growth and an overall healthy environment.
When growing a plant one of the main considerations is its growing medium. In certain specialized settings various mediums are used like plug trays, or a nutrient solution as in hydroponics; however, for nearly all plants the growing medium is going to be soil. Plants do process sunlight into food, but to make that process work the plants need to uptake complementary nutrients, and in that process plants actually mine nutrients from the soil. So for a plant to be healthy it not only needs some light exposure but it also needs soil that helps supply it with its building blocks.
There are many commercially available soils which serve well to support the healthy growth of plants. A bag of soil at the local nursery which is organic and indicated for vegetables will likely have everything needed to get started. Because vegetables often grow quick and take a lot out of the soil, soils specifically recommended for vegetables will often be well fortified for most growing situations. Once the soil is available it can be used for growing plants from seed, for transferring starts into that soil, or for using the soil in a garden or other raised bed. However, if the area is somewhat large it might be more economical to look for nurseries that will sell soil in bulk, instead of just in bags.
These commercially available soils are usually well off in terms of nutrients, but are often very dry, so should be wet slightly prior to transplanting so that any roots do not dry out; and again after any transplanting plants should always be well watered in. The soils should not look or feel dry, but also not be so wet that water can be squeezed out of it.
If you grow a plant in a pot, the pot should be filled with soil no closer than one inch from the rim of the pot, as this will allow room for water as it soaks into the soil. The soil should be well packed down without being too firm, this may sound somewhat vague, but just thinking about how to best use the soil to tuck in a little growing plant with care, often results in just the right touch. If planting seeds this same firming in of the soil is helpful. The pressure ensures that the rots are in contact with the soil which helps prevent unnecessary drying out, and the gentleness helps ensure that the soil is not too compact and unnecessarily difficult for growing root to penetrate.
Now that you have an understanding for how to work with the soil to support the health of plants there is a more in depth explanation around the various aspects of soil; specifically where soil comes from, what are the chemical components of soil, what are the biological components of soil, and how all of these elements come alive and result in inactive dirt becoming dynamically active soil.
Soil is a dynamic ecosystem composed of parent rock, elements, and abundant biology held together in a delicate balance. Like the peel of an apple the soil is only present as a thin skin around the outer layer of the Earth, and of all the land only about 3-4% is suitable for food production. To gain a basic understanding of soil it can be helpful to become familiar with where soil comes from, what is necessary for soil to be healthy and what causes soil systems to die and even become extinct. Each of the factors that make up the soil contributes to it being formed and structured in many different ways. In the US alone there are over 19,000 different soil series or varieties and an untold amount across the entire world. By understanding what makes up soil it allows for a deeper understanding of what plants are dependent upon and composed of, and ultimately what is the foundation for influencing our own health and well being.
Just as with plants and animals it is appropriate to think of there being essential nutrients for healthy soils. A child might be able to run around for much of the day after eating a bunch of sugary foods and energy drinks, but this is not the recipe for lasting sustained growth. Similarly, plants are able to show a flurry of activity after the application of artificial fertilizers, but this is not going to result in sustained growth for the plants or the planet. There are three nutrients that have long received the focus as being the most important for healthy growth, this is what is seen on the sides of bags of fertilizer; and these are Nitrogen (N), Phosphorus (P), and Potassium (K). These three primary nutrients are very important, but there are others that are also very important such as the secondary nutrients Calcium (Ca), Magnesium (Mg), and Sulfur (S); and the seven micro-nutrients Zinc (Zn), Manganese (Mn), Iron (Fe), Boron (B), Chlorine (Cl), Copper (Cu), and Molybdenum (Mo). And where we might not yet understand how or why the other elements are important it has been suggested by soil scientist that through the long process of evolution that the soil biology has found a productive use for all of the elements.