Perennial weeds will grow through most mulches, but may be weakened by the effort to reach the light and by the expenditure of additional food reserves to do so. Finally, mulches can help reduce or delay soil compaction, increasing water and air permeation into the soil. It is also easier to manually remove weeds from non-compacted soils. There are many different mulching materials. Inorganic mulches, which consist of rock, sand, gravel, cinders, and other natural materials derived from non-living sources are excellent mulches for some purposes.
Inorganic mulches serve most purposes for mulches quite well.
They reduce erosion effectively, and on slopes larger sizes of organic mulches are superior to most organic mulches because they remain in place and do not float away. Inorganic mulches isolate the soil from drying winds and sunlight, effectively reduce erosion, and help maintain constant soil temperatures. However, inorganic mulches tend to heat the air around them more than organic mulches. If the inorganic mulch is thick enough, weed problems may be reduced. These mulches can also help prevent soil compaction.