Mulches are either organic or inorganic material placed on the soil around vegetable plants. Whether you use an organic or an inorganic mulch, take care not to put it down before the soil has warmed up in the spring. If you put it down too soon, mulch will prevent the soil from warming and slow down root development.
Organic mulches are organic materials that, when laid on the soil, decompose to feed soil microorganisms and improve the quality and texture of the soil. If the mulch you've put down is decomposing quickly, add nitrogen to make up for nitrogen consumed by bacteria.
Compost: Partially decomposed compost looks a little rough, but it makes a great mulch and soil conditioner.
Lawn Clippings: Do not use clippings from a lawn that has been treated with a herbicide or weed killer; these substances can kill the vegetables you're trying to grow. Let untreated clippings dry before putting them around your garden; fresh grass mats down and smells bad while it's decomposing.
Leaves: Leaves are cheap and fairly easy to find, but they are sometimes hard to keep in place. They will stay in place better if they're ground up and partially decomposed. Do not use walnut leaves! They contain iodine, which is toxic to some vegetable plants. Nitrogen should be added to leaves.
Sawdust: Sawdust is often available for the asking, but it requires added nitrogen to prevent microorganisms from depleting the soil's nitrogen supply. If possible, allow sawdust to decompose for a year before using it as a mulch.
Straw: Straw is messy and hard to apply in small areas, but it is an excellent mulch. Be sure not to use hay, which contains many weed seeds.
Wood Chips or Shavings: Wood chips, like sawdust, decompose slowly and should be allowed to partially decompose for a year before being used as mulch. Additional nitrogen will be needed to supply bacteria during decomposition.
Landscape fabric is used in small gardens for plants that are grown in a group or a hill, such as cucumbers, squash, or pumpkins. It can also be used for individual plants such as peppers, tomatoes, and eggplants. Fabric should not be used for crops that need a cool growing season -- cabbage or cauliflower, for instance -- unless it's covered with a thick layer of light-reflecting material, such as sawdust.
What are the advantages of using an inorganic material?
There are several advantages to growing with a landscape fabric mulch. Fabric reduces the loss of soil moisture, raises the soil temperature, and speeds up crop maturity. Weeds are discouraged, because the fabric cuts off their light supply. This means you won't have to cultivate as much, reducing the risk of root damage. The fabric also helps keep the plants cleaner. When you're making a new garden in a formerly grassy area -- if you've dug up a lawn, for instance -- fabric can keep the grass from coming back.
The Disadvantages of Using Inorganic Mulch
There are some disadvantages to keep in mind as well. You will have to water more frequently, especially well-drained, sandy soils. On the other hand, plants can wilt and rot if the soil moisture is kept at too high a level and there isn't enough air in the soil.
Also remember that the fabric is inorganic, and at the end of the season you'll have to remove it from the garden. If the fabric is of high grade, you may be able to reuse it the following season.