Composting, Mulching and Improving Soils

Unlike the air we breathe or the water we drink, soil is often overlooked as an essential element in a balanced, sustainable environment. But healthy soil is critical for good air and water quality and the health of our lawns and gardens. In the Pacific Northwest, the top layer of soil is thin. And in many yards, construction and years of neglect have removed any trace of healthy soil, leaving only poor soil behind. Learn below how you can improve your soil and how composting can restore soil to make plants grow and yards healthy.

Building Soil

Human activities as diverse as constructing homes and overusing fertilizers and pesticides affect the ground beneath our feet – the soil. Regular use of pesticides and fertilizers take a toll on soil because these actions can suffocate essential soil life.
Did you know?
  • Soil provides air, water & nutrients for plants and also serves as nature's environmental protector
  • On the West coast, sand or clay form the basis for most soils and that the soil is most likely a thin layer of glacial till, not very rich in organics
  • Adding compost and mulch to soil is the best ways to improve soil health
  • Improving the soil can actually help chum and salmon

Composting

Compost is a natural organic material that is produced when leaves, plant residue, grass clippings and other yard waste break down over time.
Organic materials decompose in nature to feed soil and make it healthy. You can imitate nature in your own yard by composting your yard waste and kitchen waste. Compost is used as a soil amendment rather than a fertilizer because its nutrients become available slowly.

The Benefits of Composting

  • Encourages the growth of earthworms and other macro-organisms, whose tunneling makes room for water and air
  • Provides nitrogen, phosphorus, potassium, sulfur and micro-organisms that are essential for plant growth
  • Acts as a glue, holding water and soil particles together, and makes soil resistant to erosion
  • Binds itself to polluting metals, pesticides and other contaminants to prevent them from washing into waterways or being absorbed by plants
  • Suppresses soil-borne diseases and plant pathogens (a number of plant and lawn diseases are suppressed by micro-organisms found in compost)

Copyright: King County Solid Waste Division


Mulching

Weed control and watering are two of the biggest jobs once your garden is planted. Both of these jobs can be easier if you use mulch. The two most common kinds of mulch are plastics, and organic material such as straw, leaves, sawdust and wood-chips, clippings or compost.

Black plastic gives total weed control, keeps the soil moist and allows the soil to get warmer as we get more sunny weather. (Don't use clear plastic if you want weed control. Poke holes in the plastic so you can get water through it when you do have to water.

Organic mulches keep the soil moist and cut down on the weeding but keep the sun from warming the soil. For this reason, it is best not to put on organic mulches until the soil has warmed up, usually late June. The really nice thing about organic mulches are that you can spade them under in the fall or winter which helps improve your garden soil.

Keep in mind four cautions:
  1. Don't use grass clippings from lawns that have been recently treated with a herbicide like "Weed and Feed."
  2. Mixing in large amounts of sawdust or straw may "tie up" the nitrogen in your soil so your vegetables get yellow or stunted. Adding nitrogen fertilizer when you dig in the mulch or plant the next crop will prevent this.
  3. Loose organic mulch may provide nice, moist hiding places for slugs, so be prepared to bait for them.
  4. Some kinds of organic mulches, especially hay, may contain lots of weed seeds and make more work than they save. Check hay or straw for seed heads before buying or using.


All in all, mulches are a real labor saver. We've probably all picked dirty strawberries and gritty spinach after a heavy rain. Clean fruits and vegetables are one of the nice fringe benefits of mulching.


Copyright: WSU Coop Extension


Mulching From Yard Waste

What Is Mulch? Mulch is any material, such as wood chips, grass clippings, leaves or compost, that is spread over the surface of soil.

Grass clippings: Spread in thin layers over vegetable and flower beds, or mix with leaves and spread in a thicker layer.

Deciduous tree leaves: Spread as mulch in the fall.

Evergreen leaves: Use these on pathways because they take longer to decompose.

Chipped or shredded woody waste: Spread three to six inches deep to make a good-looking, long-lasting mulch or path cover.

What Does Mulch Do?

  • Retains water.
  • Inhibits weed growth.
  • Keeps soil temperatures from becoming too hot or too cold.
  • Protects sloping ground from soil erosion.

How Do I Apply Mulch?

  • Weed the area first, then spread mulch around plants to the drip line or cover the entire garden bed.
  • Mulch can be spread thickly if water can penetrate it to reach the soil and if it does not smother the roots of the plants being mulched.
  • Three inches of mulch can be safely used for any woody plant, and up to eight inches can be used for large trees.
  • Thick mulches are harmful to shallow-rooted plants such as rhododendrons and azaleas. Mulch should be kept a few inches away from the trunks of trees and shrubs to prevent damage to the plants from disease and rodents.

Where Can I Find Mulch Materials?

Every yard has grass, leaves or other green or woody materials that can be made into mulch. If chipped or shredded woody wastes are needed, contact tree services listed in the Yellow Pages. Some wood shops and coffee roasters make their organic byproducts available to customers and the general public. Call ahead to check on supplies.

Copyright: King County Solid Waste Division



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