The soil is the foundation of a garden. The healthier the soil, the healthier and more resilient your plants will be
. Too many of us in Arkansas are blessed with more rocks than soil, but even those who do have decent soil often lack organic matter. Building up a strong soil and amending with organic matter in the form of compost gives plants a better start in life and makes them easier to maintain. When amending soil, it is best to blend your amendments with the existing soil. Creating a homogenous mix will encourage rooting better than layering in different soil types. Working in shredded leaves, compost or manures in the fall allows them time to break down during the winter months.
Fall is an excellent time to test your soil to find out what the pH is and determine nutrient levels, so that you are prepared for the next growing season. The pH of the soil determines its level of acidity. It is measured in a range of 0-14. 7 is considered neutral, while below 7 is acid and above 7 is alkaline. Most plants like a slightly acidic soil, 6-6.5. Blueberries and azaleas like it even more acidic, getting in the range of 5-5.5. Many soils in Arkansas are acidic, and we occasionally need to add lime to raise the pH. A soil test will determine whether you need to lime or not. It will also tell you how much lime to use. Lime that can be mixed into the soil will give quicker results than lime that is laid on the soil surface.
Why is pH important? If the desired pH is too high or too low for a specific plant, the nutrients that may be in the soil will be tied up and not available for the plants to use. Azaleas grown in soils that are too alkaline will have yellow leaves with green veins, indicating iron chlorosis. There could be plenty of iron in the soil, but the plant can’t utilize it with high pH soils. Adding iron won’t solve the problem, but lowering the pH will. Tomatoes suffer more from blossom end rot when soil pH is too acidic. On the other spectrum, if the pH is too low for some plants like cabbage, beans and spinach, they will suffer from manganese toxicity and the plants will be stunted. Big leaf hydrangeas are good indicators of soil pH, as plants grown in acidic soils will have blue flowers, and those in alkaline soils will have pink blooms. Hydrangeas can grow in a wide range of soil pH, but other plants need more specific ranges. Knowing the pH of your soil is important.
To test your soil, take slices from the surface down to a depth of six inches. Get a slice or core of soil from 6-10 different spots in your yard or garden for each soil sample you are taking. Mix it together and take one pint of soil for each sample into your local county extension office. Many gardeners test their lawns, vegetable gardens and flower gardens separately, since they treat them differently. Within two to three weeks you will get a computer printout mailed to you with the results, and recommendations on whether your garden needs lime, and what nutrients are needed.
Besides testing soil pH and fertility, now is also a great time to test soil drainage. Most plants don’t swim well and standing in wet feet for any length of time can lead to root problems. To test soil drainage, dig a hole the depth your plants would be growing (depth will vary based on whether the plants are annuals, perennials, shrubs or trees). Fill the hole with water until the water stands. In a well-drained soil, the water should go down about an inch per hour. If there is too much sand, it may never hold water, so adding organic matter will help. If there is still water standing in the hole days later, drainage is an issue. Figure out your drainage problems and solve them — whether by putting in drains, altering the terrain, or building raised beds.
While many gardeners spend their time and efforts on what plants to grow, garden success will be easier to attain if you start from the ground up!
Janet B. Carson is an extension horticulture specialist for the University of Arkansas Cooperative Extension Service.