• Castings are close to neutral in pH- around 7 on the pH scale – no matter what kind of soil the worm ate. For example, even if a worm fed in a very acidic soil, its castings would be neutral, not acidic. Earthworm castings also contribute to neutralizing soil pH by adding calcium carbonate to the soil.
  
• Castings are rich in minerals and nutrients needed by plants. A study at Cornell University showed that the nutrient level of casting is usually much higher than that of the surrounding soil. Castings were found to be high in nitrogen, potassium, phosphorus, magnesium, and trace minerals. Castings were also shown to supply needed micronutrients to plants. Another study estimated that castings contain five times the available nitrogen, seven times the available potash, and one and a half times the calcium found in good topsoil. So castings are excellent plant fertilizers and provide nutrients in a form immediately available for plant use.
  
• Castings are food for other beneficial microorganisms. They will contain thousands of bacteria, enzymes, and remnants of plant and animal material that were not digested by the earthworm. The composting process then continues long after the casting is excreted, adding beneficial microorganisms back to the soil and providing a source of food for the ones already there. Some of these soil organisms release potassium, phosphorus, calcium, magnesium, iron, and sulfur into the soil read for plant use.
  
• Castings increase the humus content of the soil. An excreted casting is 65 to 70 percent organic matter, or humus. Soil rich in humus soaks up and holds water better. The soil is loose and is less likely to become hard and compacted. Humus can also buffer soil by binding with and holding the heavy metals from materials such as manure, (stems and roots) left over from crops.
  
• Castings hold their nutrients in mucus membranes that are secreted by the earthworm. This allows the nutrients to be slowly released so they are available to the plants over a period of time as needed.

             Extracted from:
             Nancarrow, Loren and Janet Hogan Taylor. The Worm Book. Berkeley, CA: Ten Speed Press, 1998.

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