p lants and soil organisms like a varied diet. Adding organic matter in _ different forms — mulches, topdressings, soil amendments, and green manures — ensures that both get a balanced supply of micronutrients. It can also make life easier for the gardener, as different methods of adding organic matter suit individual budgets, schedules, and energy levels.
Some methods are better suited to specific situations. Green manures are great when starting new gardens, and in a crop rotation in vegetable or annual beds. Maintaining a 2-inch-thick layer of coarse compost mulch keeps an ornamental shrub border, flower bed, or foundation planting supplied with organic matter. If slugs or snails keep you from using mulch, substitute a short-term, well-decomposed topdressing. When you renovate a Perennial bed or divide the plants in a large area, incorporate_sml amencl-ments to give plants a head start, supplementing each year with topdre^ «8 or mulch. Whichever method you choose, use overall garde, heaUh and Performance, plus periodic earthworm counts, as indicators of adequ organic matter. , . „m, wav 0f
Striving for high yields in the vegetable gardems one great w ^¡ng organic matter. The same soil conditions that p^ thel^ ^ "J also promote a large and healthy ^^^ a„d a J* amounts of organic matter, slightly have
In This Chapter
Types of Mulches
Using Organic Mulches
Using Fabric, Paper, and Plastic Mulches
Using Soil Amendments
Legumes and Grasses
Growing Green Manures and Cover Crops
Green Manures for Special Purposes
Combination Cover Crop and Mulch
Mulching is one of the easiest ways to add organic matter: Spread the material on top of the soil and let earthworms do the tilling for you. Mulching (or its close cousin, topdressing) is often the only way to supply organic matter to trees, shrubs, berry bushes, and perennials. If these are shallow-rooted, they'll resent any attempt to dig in amendments. Its much safer (and simpler) to spread organic materials on top of their roots. As a bonus, mulching greatly reduces watering and weeding chores. In addition to adding humus, mulches improve the soil in many ways, from reducing erosion to encouraging soil organisms.
Not all mulches provide organic matter and nutrients — only organic ones do. Organic mulches can be anything you'd put in the compost heap. For mulching, though — unlike composting — the longer something-takes to break down, the better. Wood chips and bark nuggets that are too hard for the compost heap are perfect for mulch. They don't need to be replenished as often as a mulch of grass clippings.
A few warnings are in order before you mulch everything in sight. In wet soils and very humid climates, organic mulches can promote some diseases and increase chances of rot. If spread too thickly, they can interfere with the soil's air circulation. Fresh, unweathered carbon-rich mulches such as sawdust can temporarily tie up enough soil nitrogen to interfere with plant growth. This problem is easily solved by letting them weather until their color fades, or by spreading nitrogen-rich material underneath them. Often, these same materials are flammable and should be used with care in fire-prone areas.
Inorganic mulches provide some benefits, although they don't supply organic matter. It's a good idea to spread 1 to 2 inches of compost or aged manure over the soil before using inorganic mulches. Once they're in place, it's hard to replenish soil organic matter. Here are a few inorganic mulches, and reasons why you might want to consider using them.
DID YOU KNOW
Mulches that disappear very quickly are more properly called top-dressings. The purpose of a topdressing is to get organic matter and nutrients into the soil as quickly as possible. Mulches need to stick around a little longer to fulfill their main purpose, which is providing a protective blanket for the soil. Providing humus and nutrients is really a secondary benefit of mulches, especially since they often take a long time to break down and release either.
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