Improving the soil used to grow your vegetables is one of the best ways to see bigger plants, more produce and fewer problems. In general, garden soil should be loamy (or sandy and loamy), with plenty of organic matter. Thankfully, if you have not been blessed with an ideal soil, you can create your own.
Soil should be tailored to meet the needs of specific vegetables whenever possible to improve your results. For example, tomatoes require plenty of organic matter and acidic soil where carrots cannot tolerate the same acidity and prefer a loose soil without stones or clumps.
Loosen the soil by tilling or digging and turning. Roots will be able to more easily penetrate soil that has been broken apart. This process also helps create pockets of air to supply oxygen that roots need to thrive. Heavy clay soil compacts, holding too much water, preventing air from getting to roots and roots from being able to develop well.
Improve drainage. According to Mississippi State University, heavy soils like clay don't drain well, while sandy soil may drain too quickly. Grade (create a gentle slope) or level (fill in low spots) areas prone to accumulating standing water to encourage rain to drain properly. In very poor soils or areas with drainage trouble that resists repair, raised beds may be a better way to garden.
Add organic matter to increase the level of nutrients available to plants. Organic matter can help hold water and keep roots moist. It can also be used to improve very sandy, clay ridden or densely packed soils.
Add soil conditioners to improve structure. These include sawdust, coarse sand and perlite. Some additions do double duty as conditioner and organic matter, including compost and peat moss.
Plant a cover crop. Also called green manure, cover crops include legumes (such as clover and vetch) and cereal grains (like oats, wheat or rye). Such growth keeps weeds out of the garden space during months it is not in use, adds nitrogen and fertility to the soil and fights erosion. According to the National Sustainable Agriculture Information Service, beneficial microbes break down the green manure, releasing its nutrients; in this way, by tilling them directly into the soil, these cover crops improve the soil for the next crop.
Test the soil pH. Soil pH makes different nutrients more or less available to plants for use. According to NASA's Soil Science Education Page, certain plants require specific amounts of various nutrients (Nitrogen, Potassium and Phosphorous in particular) in order to resist disease and achieve their best rate of growth.