About Soil pH

• Soil pH affects the availability of soil nutrients and the toxicity of minerals within soil. For instance, high acidity in soil reduces the availability of potassium, calcium and magnesium, while increasing the availability of potentially harmful amounts of iron, aluminum and zinc, according to University of Florida professors Amy L. Shober and Geoffrey C. Denny. Highly alkaline soils are associated with deficiencies in zinc, manganese and iron. Soil bacteria also affects the bacteria and microbes within the soil and can contribute to the incidence of plant diseases. Soil test kits will indicate the pH of your soil, so you can adjust the acidity or alkalinity as needed. Your local agricultural extension service can also assist you with testing and determining what you can do to optimize soil conditions for your plants.
  
  

Hydrated Lime

• Lime is a material made from calcium, sometimes mixed with magnesium, used to raise the pH of soil. It can be made from oyster shells or various industrial byproducts. When this material is heated and then mixed with water, it forms hydroxides. This treated lime is called hydrated lime. It is bulkier than ordinary lime and can be difficult to apply. Generally, hydrated lime is used when plants are not yet present in the soil because it can burn the root systems, according to the North Carolina Master Gardener Program website.
  
  

Adding LIme To Soil

• Hydrated lime is added when the soil pH drops so low that it creates conditions inhospitable for plant growth. This can occur as a result of natural soil acidity or from the continued use of nitrogen fertilizers, which tends to lower pH. Farmers and gardeners use hydrated lime to quickly raise soil pH, which makes soil more alkaline. The lime is worked into the soil, not merely laid on the surface. Apply the lime gradually, testing periodically.
  
  

Lime Precautions

• At no time should the soil pH register above 8.0, according to Oregon State University writers Jay W. Johnson and Don Myers. Soil pH this high will burn plant roots. You will then have to add sulfur to the soil to bring the pH down. Wear gloves, protective clothing and a respiratory mask when working with lime products.