Either organic or inorganic mulches may be used in the home garden. Common organic mulches include straw, grass clippings, leaves, compost and rotted sawdust. The most common inorganic mulch is black plastic. Both organic and inorganic mulches reduce weed growth and conserve soil moisture. Organic mulches also improve soil structure and water-holding ability. They increase soil organic matter and eventually improve soil nutrient content. Black plastic mulch also increases soil temperatures.
Apply organic mulches around established plants in a layer 2 to 4 inches deep. Organic mulches are generally light-colored, reflect sunlight and keep the soil cool longer in the spring. They work best on cool-season vegetables early in the spring and on warm-season vegetables after soils warm. Add 1/4 pound of ammonium nitrate fertilizer or its equivalent to each bushel of mulch.
Apply black plastic mulches over freshly fertilized and worked soils several days before planting. Shape the soil surface so drainage is toward the plants and use strips of plastic, not sheets. This will help water to reach the plants. It is important to thoroughly cover the edges of the plastic with soil to prevent wind damage. Insert plants or seed through holes or slits cut in the plastic. Because black plastic absorbs sunlight and warms the soil, warm-season plants such as tomatoes, eggplant, watermelon, peppers and cantaloupe can be set through plastic about a week earlier than they can be planted in bare soil. The first harvest of these crops will also be earlier when black plastic mulch is used. Because black plastic mulch warms the soil, it is not well suited to cool-season vegetables.
One disadvantage of black plastic is that it must be removed from the garden and discarded after the growing season. Another disadvantage is that it is hard to water or to apply nitrogen sidedressings under plastic. You can lay black plastic over a trickle irrigation tube and water
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