5 lb bag. Limestone is a natural mineral that helps neutralize soil acidity, improves soil structure, and increases the availability of elements in soil. 100% natural soil supplement restores soil pH levels. Good soil requires more than just tilling and watering. The proper acid level, or pH balance, has to be present to grow plants successfully. When plants perform poorly a high or low pH level can be major contributing factor.Limestone is a naturally occurring mineral that can be used to help rejuvenate fallow soils. Using Limestone can recondition your soil to achieve its maximum growing potential.