Mulch can save around 20-30% of your water usage, but this is a conservative estimate and in some cases you can save up to 70%. A recent cost benefit analysis using yield data from vines in South Australia showed that compost mulch applied at 10 and 50mm gave strong returns on the initial investment. When mulch was applied to 50mm depth (at $24.50/m), an average of $2.60 was returned on a $1 investment. This makes compost mulch great value for money.