Wood ashes also raise soil pH with twice as much ash applied as limestone for the same effect. Ashes should not come into contact with germinating seedlings or plant roots as they may cause root burn. Other amendments are added specifically to improve soil nutrient levels. Greensand and granite meal are sources of potassium. Granite meal is finely ground granite rock that releases its potassium slowly.
Greensand is relatively low in potassium, which is readily dissolved.
Neither should be considered a sole nutrient source. Both materials may be hard to find in some areas. Other nutritional amendments that can be purchased for garden use include cottonseed meal, kelp meal, leather meal, and worm castings, as well as an array of synthetic fertilizers. The organic amendments are particularly useful where a trace element deficiency exists, while synthetic fertilizers are generally more available, less expensive, and have quicker results. However, these inert materials can be expensive and extremely large quantities are needed to do any good.