The best soil for a vegetable garden soil is loose and well draining. Drainage is important because roots need to neither be drowned in trapped water, nor dry out in soil that water passes through too quickly.
Clay soil is good for vegetables in that it tends to be rich in nutrients, yet it can also be poor in not allowing sufficient aeration and drainage. On the other hand, soil that is too sandy may lack nutrients and may allow too fast drainage and have a tendency to dry out. So what’s needed is something in between.
If you start off with a heavy clay soil, you can add builder’s sand or sandy loam soil to improve drainage.
Vegetable garden soil should contain at least 20% organic material to hold nutrients for plants. Organic material also softens soil and makes it easier for roots to spread.
You can increase your soil’s organic matter by adding manure or compost, or by adding fresh sawdust or barkdust along with extra nitrogen. You can also turn under plant residues like soybeans, rye, pea plants, or sweet corn stalks after harvest.
The best thing to do is to have your soil scientifically tested to see how it breaks down chemically and what it may need. This can be done at most garden centers where you buy your supplies. The three main categories of nutrients are nitrogen, phosphorus, and potassium. If your soil does not contain these in the proper balance, there are chemical fertilizers that have extra of one or another that you can use to adjust that balance.
If you choose to make these adjustments organically, manure and nitrogen fixing plants such as legumes are good when nitrogen is lacking. To boost the phosphorus, bone meal or rock phosphate can be used. To add potassium, good options are potash, wood ash, or greensand.
A chemical analysis will also tell you if your soil lacks the necessary trace amounts of minerals and nutrients such as boron, calcium, chloride, copper, iron, manganese, molybdenum, and zinc. In addition, it will measure the pH of your soil, which for most vegetables should be in a range from about 6 to 7.
When you need to add amendments to the soil, don’t do so when the soil is too wet. It should be crumbly to the touch. It’s best to start with dry soil, water it lightly, let it soak in for a day or two, and only then add your amendments.
You’ll also want to examine your soil and make sure it is free of weeds or excessive pests and disease.
If you start with good healthy soil, that has plenty of organic material for nutrients, and drains well but not too fast, you give yourself the best odds for a thriving garden of great tasting vegetables.
Rod Smith, “Planting a Vegetable Garden.” Rod’s Garden.
“Vegetable Garden Soil: Soil Requirements For Vegetable Plants.” Gardening Know How.
“Vegetable Gardening in Mississippi.” MSU Cares.