Mulch

Mulch is a layer that lies on top of the soil's surface. It's a great way to feed plants, help retain moisture, insulates against cold and heat, suppress weeds, and reduce erosion.


Types
Processed materials like rubber, geotextiles, paper, mulch mats, or even hessian.

Stone - from a sensible source - no nutritional value but great for keeping weeds down and maintaining temperature, also decorative stone can be used. From experience algae will stain stone that is in shade. Tt is also a pain to pick dirt and plant matter from a stone mulch.

Wood - again, from a sensible source - wood materials should not be treated with chemicals. Also, wood is nitrogen deficient and can deplete soil nitrogen when breaking down so

Seaweed freshly washed up that hasn't accumulated salt from sea-spray, rinse it as well - Good blog article and comments.

Manure and compost are great for feeding the soil although make sure the mulch doesn't touch plants and trees as it may burn them or cause unnatural growth. As a general rule a gap of an inch or two around stems and trunks.

Straw can be messy but will break down providing nutrients. Good example of straw use on Gardeners' World site.

Coffee grounds can be used as a mulch for acid loving plants, here's a link with more information about it's use. When coffee is composted the acidity is neutralised so it can be used on normal ph crops.

There is a method of mulching that involves a layer of straw and organic material is added underneath this. Such a method skips the compost heap and goes straight to the soil - more detail here.

Compost Crops
Also called green manure, cover crops are a type of living mulch. Here's an article.

Usage
If using an auto watering system the network of pipes can be under the mulch layer ensuring water goes straight to the plant and minimizing water loss.

Sources & Information
Beginners guide to mulching from Biodelice
Detailed article about mulches from Lowes
[1]Strawberry and straw mulch - GW