Mulches have several effects on the soil which help to improve plant growth:

• Decreasing water loss due to evaporation

• Reducing weed growth by reducing the amount of light reaching the soil

• Preventing soil erosion

• Increasing the number of micro-organisms in the top soil

• Adding nutrients to the soil and improving soil structure

• Adding organic matter to the soil

Alternative mulching materials include black plastic sheeting or cardboard. However obviously these materials do not add nutrients to the soil or improve its structure.