Jonathan Green's Mag-I-Cal Plus for lawns in acidic and hard soil contains calcium carbonate in a completely soluble form that is immediately available to adjust soil pH upwards. Poor soil is often the problem in growing a great lawn and calcium is vital to many grass plant functions. When soil is compacted or too acidic, air, water and nutrients are unable to reach the roots, making it very difficult for grass to flourish. Lawns thrive in soil with slightly acidic to neutral pH levels ranging from 6.2 to 7.0. When pH levels drop between 4.0 to 6.0 weeds flourish and the grass becomes light green and spindly. Additionally, Mag-I-Cal plus helps to break up clay and compacted soils. This improves root penetration and promotes growth by increasing biological activity and releasing nutrients trapped in the soil.