Mulch protects vegetable plants by keeping harmful sunrays from the plant roots and surrounding dirt. This keeps the water in the soil from evaporating too quickly, leaving the plants to dry out or wilt.
Mulch releases nutrients right back into the soil which is critical for growing vegetables.
Straw mulch is helpful because it's light and airy. The weight keeps plants from getting rot at the base. Make sure you buy straw that doesn't have seeds and that you stay on top of any weeds if they come up.
Composted manure is good for gardens because it adds so many nutrients. Fresh manure can have a lot of seeds that cause weeds, but they're all broken down in the compost. You can use fresh manure to fire up a compost pile or to create heat in a hot frame.
When mulching, you walk a fine line between protecting the plants from drying out and covering them too much so they rot.
Mulch does a great job of keeping weeds out and moisture in, but it has another huge benefit. The very dirt that gives a plant structure and nutrients can hold diseases that can harm it. Soil-borne diseases occur when water splashes dirt up onto the plant stem or leaves. Mulch makes a barrier between the ground and the plant to reduce the risk of these diseases.
When you apply mulch, make sure you can't see the soil below when you are finished. A coating of 2-4 inches will work, depending on the type of mulch you use. Heavier mulches can be applied in a thin layer, and lighter mulches in a heavy layer. You'll need to reapply mulch as it thins out and breaks down into the soil, possibly 2 or 3 times during the growth of a plant.