About Mulches

To mulch is simply to cover the soil around plants with a protective material, organic or inorganic. Purpose, availability, cost, and final appearance of mulch will be the determining factors in choosing which type to use.

Using mulch can help you and your garden in many ways.

· Reduce weed growth by making it difficult for seeds to germinate or weeds to emerge.

· Maintain uniform moisture. Evaporation is decreased and rain is absorbed evenly.

· Soil erosion and soil crusting is decreased. Reduced splashing of soil onto the fruit, leaves cleaner fruit and helps prevent disease.

· Soil temperatures are modified. Plastic mulches warm soil more quickly in spring, Organic mulches insulate and are applied later in the season.

· Organic mulches add nutrients and humus to the soil as they decompose, improving its tilth and moisture-holding capacity.
Organic Mulches
Apply organic mulches after plants are well established (4 to 6 inches tall), weeds are removed, and there is moisture in the soil and before hot weather.

Sawdust - A 2-inch layer of sawdust provides good weed control. If applied around growing plants, add 1/2 pound of actual nitrogen per 10 cubic feet of sawdust to prevent nutrient deficiencies. Fresh sawdust contains a great deal of carbon and very little nitrogen, and its breakdown requires that microorganisms take nitrogen from the soil. Sawdust is best used for garden paths and around permanent plantings. Readily available from sawmills, it tends to be inexpensive.

Hay or straw - A 6- to 8-inch layer of hay or straw provides good annual weed control.
These materials decompose quickly and must be replenished to keep down weeds.
Grass clippings - A 2-inch layer of grass clippings provides good weed control. Build up the layer gradually, using dry grass. A thick layer of green grass will give off excessive heat and foul odors rather than decompose as other organic material.

Leaves - A layer of leaves, 2 to 3 inches thick after compaction, provides good annual weed control. Leaves will decompose fairly quickly, are usually easy to obtain, attractive as a mulch, and will improve the soil once decomposed. To reduce blowing of dry leaves, allow to decompose partially. Note: Leaves of the black walnut tree (Juglans nigra) are an exception due to the presence of juglone, a chemical that inhibits growth of many plants.
Bark and wood chips - A 2- to 3-inch layer of bark provides good weed control. Wood chips are slower to decay than shredded bark, and can used as a pathway material in raised beds.

Inorganic Mulches
Apply inorganic mulches prior to planting on completely prepared soil with high moisture level. Bury edges to prevent it from blowing away. Cut slits for seeding or setting transplants. A few additional slits can be made to allow water to infiltrate.

Black plastic - One layer of black plastic provides excellent weed control. It is relatively slow to decompose, but will be somewhat broken down by sunlight and must be replaced every two years at least. Black plastic mulch will increase the soil temperature by about 8°F in the spring. It may cause soil temperatures to rise too much in mid-summer, damaging the roots of plants unless a good foliage cover or organic mulch prevents direct absorption of sunlight. Check periodically to see that soil remains moist beneath the plastic; cut holes in it if water doesn't seem to be getting through. Black plastic is easy to obtain, but is fairly expensive. A new type of black plastic has recently come onto the market which has a white, reflective side to prevent the overheating problems experienced with solid black plastic. Another plastic is porous to allow penetration of water and exchange of gases between the soil and air.

Newspaper - Using 2 to 4 layers of newspaper provides good weed control. It decomposes within a season and is readily available and cheap. Cover with an organic mulch, such as sawdust or hay, to hold paper in place. Excellent for use in pathways and around newly set strawberry plants.

Red plastic - Developed and patented by scientists with the Agricultural Research Service and Clemson University, red plastic mulch boosted tomato yields in research plots up to 20 percent, while conserving water and controlling weeds. Red plastic mulch reflects onto plants higher amounts of certain growth-enhancing light waves from sunlight. In 3 years of ARS field tests, red mulch boosted tomato size and weight by increasing the plant's growth above the ground--especially in the fruit. The scientists say the mulch can improve strawberry flavor by changing the fruit's chemistry.


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