You can do everything right–pick the right seeds or plants, water carefully and on schedule, use the right fertilizer, and your garden will still disappoint you if you don't start with good soil. How can you know if your soil is good and what can you do to make it right?
Acid vs. Alkiline
Actually, it all boils down to how acid or how alkaline your soil is, and pH is the measurement used to indicate this balance. When your soil is in balance, it measures pH7 and is said to be neutral. A score of 0 says your soil is very acidic. A measure of 14 says it is very alkaline or basic. Yours is probably not at either of these extremes. You will need to take steps to maintain a balance because your soil will go one way or the other over time. For the organic gardener, pH is very important. For one thing, certain plants prefer acid conditions while others prefer alkaline. Also, some diseases will be more inclined to become a problem when the soil is either acidic or alkaline. In addition, pH will play a role in how well your plants will be nourished, since some nutrients are not available in acidic soil and some not in alkaline soil.
Nutrient Availability in Relation to Soil pH
Most of the things you grow will do better in a neutral or slightly acidic pH. The reason is that nutrients are dissolved better at pH 6.3 through 6.8. On the other hand, there are some that require more acid such as potatoes and strawberries and some that require.
The nutrients your plants need are nitrogen, phosphorus, potassium, sulfur, magnesium, and calcium and some other elements in very small amounts. In pH that is below 5.5 these minerals will not dissolve and won't be available for the roots of your plants. However, there are some minerals that will dissolve at that pH level, but there may be too much of them and they may be toxic in these acid conditions. If your plants are being deprived of the nutrients they need, the stems will be thin, the leaves will be yellowed or mottled, and their growth will be stunted. At the same time, you need to know that this is not a once-and-done situation. pH will vary in both soil and water seasonally or even daily. Rainfall, growth of organisms in the soil, and even the temperature will affect pH. Also, the pH may be different on the surface than it is at other levels. What all this says is the pH should be measured from time to time and not just at the surface level.
Measuring Your pH
Many garden stores and other service providers offer pH measurement services. However, it is possible to do this yourself by buying an inexpensive kit. You will use it to mix a sample of your soil with water, and the color of the water will indicate whether it is acid or alkaline. You can also use litmus paper. Mix a small sample of your soil with distilled water and put a strip of litmus paper in the solution. The paper will turn red if the soil is acid and blue if it is alkaline. There is also a more expensive electronic pH meter that is a little more sophisticated. Visit a garden store and talk to one of the soil experts there about testing your soil. Also, you may have a county extension agent who can be helpful.
Adjusting Soil pH
To adjust the acid in your soil, you will want to add some of the elements that are lost, such as calcium. This can be done in several ways. You can add ground limestone or ground chalk, for instance. These are natural forms of calcium carbonate. This is what is usually used for gardening because it costs less than anything else and you can put it on your soil at any season of the year. These don’t react very quickly; for that reason the influence on plant growth and soil fertility is steady. It will also last for a long time. This should be applied about one to two pounds per yard of soil. Another possibility is calcium sulphate, which is also known as gypsum. It is useful for treating acid soil. It is also useful for breaking up soil that is heavy with clay. Talk to the experts in a gardening store about where to obtain these minerals. If your garden is still not meeting your expectations, your county agricultural agent or an expert at a garden store may be able to advise you. Sometimes, a local college will have an agriculture program and may be offering mini-courses for gardeners. It would be worthwhile to look into them and also consult with faculty members for advice about testing your soil.
By TTS Cofounder Botanical Chef Omid Jaffari