#3 Nurture the soil

When is soil more than just dirt? When you want to grow healthy plants in your yard and garden, look at soil as an important part of the growth of your plants, just like water, sunlight, and controlling pests. You can improve your soil’s ability to support thriving plants of all kinds by protecting it from compaction, amending it with nutrients, and adding mulch as a top dressing.

Protect Soil From Compaction

Why?

Compacted soil has less air and is less porous. This means it is harder for roots to grow through and harder for roots to get air.
Compacted soil affects plant growth – restricted roots are often unable to take up sufficient water or nutrients from the soil, resulting in reduced plant growth, particularly during periods of drought.
Compacted soil can either hold water in (bad drainage) or keep water out.
A large number of organisms make up the soil food web. They range in size from tiny one-celled bacteria, algae, fungi, and protozoa, to nematodes, earthworms, insects, and plants. These organisms are beneficial to plant health but cannot live in compacted soil.

How?

Keep foot traffic limited to a few areas in the garden by using consistent pathways to navigate your yard.
Avoid walking on wet soils and areas where you have recently loosened the soil.
Periodically aerate lawn areas using a soil aerator that removes plugs from the surface of the lawn.
Adding compost can help alleviate soil compaction by improving soil structure, aeration, and water holding capacity. See Amend Soil below.

Amend Soil

Why?

Soil amendments improve the physical properties of soils. They increase the water and nutrient-holding capacity of soil and improve aeration and water infiltration. Soil amendments are more than just fertilizer. Fertilizer only adds nutrients to the soil, while soil amendments, such as compost, humus, or worm castings improve soil by making its texture and drainage more conducive to plant health. Soil amendments add nutrients to the soil, improve water-holding capacity, and loosen heavy soils.

How?

Mix into your annual garden beds a ½"-3" layer of soil amendment such as compost, humus, worm castings, etc., at least once a year.
Amend your planting beds with good quality compost before planting turf, annuals, perennials, trees and shrubs. Compost is filled with beneficial microorganisms. The long and short-term benefits include faster plant establishment, decreased fertilizer and pesticide use, and reduced water bills.

Mulch

Why?

Using mulch in your landscape:

Smothers weeds
Retains soil moisture
Moderates soil temperature
Feeds the soil by adding organic matter as the mulch breaks down
Alleviates soil compaction

How?

Spread a 2-4" layer of organic biodegradable mulch over tree roots, shrubs and plant beds as appropriate.
Replenish annually or as needed to keep a 2-4" layer. This depth is ideal for weed suppression and water conservation.

You can choose organic or inorganic mulch. Each has its uses:

Organic mulch

Yard waste – grass clippings, leaves, and small twigs can be used as
mulch in moderation, and are good for use behind bushes or borders. Mulching with yard waste functions better when it is composted first.
Straw keeps weeds down and is good for vegetable gardens, but must be replenished often and is less attractive.
Pine bark and pine needles are good for weed control. Bark lasts longer, but needles are more water-permeable.
Wood chips – bark and wood pieces of various sizes are attractive in landscapes and provide good weed control and water conservation.

Inorganic mulch

Rocks and gravel are good for weed suppression and stay in place. They are fairly inexpensive, but heavy and labor intensive in large quantities.
Black plastic is not recommended for use around landscape plants because it does not allow water, nutrients or air into the soil, though it is good for water conservation and weed control.
Landscape cloth is a woven material that air and water can move through; it is good for weed control.

More Info:

Nurture the Soil StopWaste.Org (Alameda County Waste Management Authority and Alameda County Source Reduction and Recycling Board)

Choosing a Soil Amendment, Colorado State University Extension

Soil Testing, Fertilizers, and Soil Amendments, US Department of Agriculture, Natural Resources Conservation Service

Soil Organisms (pdf) University of California Agriculture and Natural Resources

Complete Mulch Guide, Weekend Gardener