I find that people are often confused by the words Compost and amendments.
Mulch is basically any product applied over the surface of the dirt, to both cool down or to warm the dirt and at the same time preserve water. It may be more proper to contact Compost, surface Compost. Mulch is commonly used to keep the dirt cool and to preserve water by preventing the water from evaporating out of the dirt. Mulches will be organic components like decorative bark, compost or even straw. Mulches will also be inorganic like decorative rock, gravel or sand. Amendments are components added into the dirt to improve the physical or chemical make-up of the dirt.
Cooling mulches are very good for vegetable gardens and flowerbeds during hot weather. Mulch helps keeps the dirt cool and evenly moist, which benefits both flowers and vegetables. Cooling mulches include compost, decorative bark (all sizes and types) and even newspaper. Newspaper will be a problem because it blows real easy, and the colored papers will release ink, which will become a problem.
In your vegetable garden, straw will also be a good Compost. Straw will be spread out during the summer time and then eliminated and composted at the end of summer time allowing the dirt to heat up in the fall. Straw or sawdust will become a problem if left on the dirt too long. Even on top of the dirt, straw or sawdust will deplete the nitrogen out of the dirt.
Besides conserving water, mulches have other benefits. Mulches will both cool down or heat up the dirt. In late spring or early summer time we will place clear or dark plastic material over our garden beds. Just cut holes in the plastic material to plant your summer time vegetables. The plastic material will heat up the dirt and allow vegetable seeds to germinate faster and the plants to grow faster.
As the summer time heats up, cover the plastic material with straw or compost or other organic material about three inches deep. This will cool down the dirt during the hot months. When the summer time fades into fall remove the organic Compost and expose the plastic material, so the dirt will stay warm and your vegetables continue to grow.
That is an illustration of how to use mulches in your garden and how to expand your flourishing season. Even if you do not use the plastic material layer, a cooling Compost in the summer time is very important and will benefit your garden.
Mulches will also prevent weeds by suffocating weed seeds. With three inches of Compost, very few weeds will grow and those that do grow will easily be pulled out.