A pH soil test will tell you whether your soil is within the optimum range or whether it will need to be treated to adjust the pH level. Although the optimum range is 5.5 to 7.0 some plants will grow in a more acid soil and some at a more alkaline level.
PH is not an indication of fertility, but it does affect the availability of fertilizer nutrients. The soil may contain adequate nutrients yet plant health may be limited by an unfavorable pH level. On the other hand, builder’s sand, which is devoid of nutrients, may have optimum pH for plant growth.
To correct the pH of or “sweeten” an acid soil (5.5 to 0.0) use lime or dolomite. Lime contains mainly calcium carbonate and dolomite contains both calcium carbonate and magnesium carbonate. Ground limestone and dolomite are less likely to burn plant roots than hydrated lime and is therefore recommended for home use. The greater the amount of organic matter or clay in a soil, the more lime or dolomite required to change a pH level. The best results will be achieved if you incorporate the lime uniformly at least six inches into the soil.
If soil is too alkaline you should determine if it is due to a soil characteristic or lime application. It is very difficult, if not impossible, to change appreciably the pH of naturally alkaline soils by using sulfur, ammonium sulfate, or similar acid forming materials. If this high pH is due to applied lime or dolomite, acid forming materials like sulfur or ammonium sulfate can be applied. To decrease the soil pH use superfine dusting or water soluble sulfur. Repeat applications of sulfur should not be made more often than once every two months because soil sulfur oxidizes and mixes with water to form a strong acid that can burn the plant roots — so use it with caution. It takes approximately 1/3 the amount of sulfur to decrease the pH one unit as it does limestone to raise soil pH one unit. Our soil on Marco Island is mostly alkaline due to the high sand and shell content. Using sulfur coated fertilizers is a helpful practice. These coated fertilizers are the slow release kind which is a more environmentally friendly way to fertilize and it slowly adds some much needed sulfur to you landscape.
Desirable soil ph for optimum crop production pH range
The desirable pH range for optimum plant growth varies among crops. While some crops grow best in the 6.0 to 7.0 range, others grow well under slightly acidic conditions. Soil properties that influence the need for and response to lime vary by region. A knowledge of the soil and the crop is important in managing soil pH for the best crop performance.
Soils become acidic when basic elements such as calcium, magnesium, sodium and potassium held by soil colloids are replaced by hydrogen ions. Soils formed under conditions of high annual rainfall are more acidic than are soils formed under more arid conditions. Thus, most southeastern soils are inherently more acidic than soils of the Midwest and far West.
Soils formed under low rainfall conditions tend to be basic with soil pH readings around 7.0. Intensive farming over a number of years with nitrogen fertilizers or manures can result in soil acidification. In the wheat-growing regions of Kansas and Oklahoma, for example, which have soil pH of 5.0 and below, aluminum toxicity in wheat and good response to liming have been documented in recent years.