PDF: "Nurture the Soil"

Soil is a complex, dynamic combination of minerals, air, water and organic matter. And although organic matter is a small fraction of the soil, it is a vital component. It includes plant and animal debris in various stages of decay as well as many living organisms-one teaspoon of a healthy soil can contain billions of beneficial bacteria and fungi.

A cornerstone of Bay-Friendly landscaping is the proper protection and ongoing care for the soil organisms. It is based on the principle of feeding the soil, not the plant, to encourage a thriving community-a foodweb-of microorganisms, worms and other beneficial creatures. Healthy soil is alive!

Why Does Soil Life Matter?
Living soil is teeming with bacteria, fungi, worms and other beneficial organisms-amazing workhorses that will carry out the following valuable processes:

• Creating soil structure
• Storing and cycling nutrients
• Protecting plants from pests
• Improving water infiltration and storage.

Some practices that you can implement to nurture the soil include:

1. Removing and storing topsoil during construction.
2. Protecting soil from compaction.
3. Defending against erosion.
4. Amending the soil compost before planting.
5. Grasscycling.
6. Mulching regularly.
7. Aerating compacted soils.
8. Feeding soil naturally with compost topdressing or tea.
9. Avoiding synthetic, quick release fertilizers.
10. Minimizing the use of chemical pesticides.

1. Remove and store topsoil during construction
Topsoil is a valuable resource, yet it is typically removed or mixed with subsoil during construction, beginning a cycle of high water and chemical dependency. Conserving topsoil can reduce the likelihood of many problems over the long run, including stormwater runoff. It can minimize fertilizer and irrigation requirements and topsoil replacement costs.

2. Protect soil from compaction
Heavy equipment can compact soil as deep as two feet below the surface of the soil. Compacted soils do not have adequate space for air or water. Protecting against compaction ensures that soil structure and the soil's ability to support the microbes that cycle nutrients and filter pollutants are protected.

3. Defend against erosion
With exception of a few large trees, native vegetation is also typically removed from a site before building or landscaping. Doing so exposes the soil to erosion, especially along slopes and waterways. The resulting loss of topsoil depletes the soil of its organic, living component and clogs our waterways. It turns nature on its head by turning a valuable resource into a pollutant. One effective practice for preventing erosion where vegetation has been removed is spreading mulch.

Looking for more information? Check these pages to learn more about BMP's, including using compost and mulch to control erosion:

• www.ciwmb.ca.gov/organics
• www.cleanwaterprogram.com

4. Amend the soil with compost before planting
Compost is thriving with microorganisms-one teaspoon can have more than one billion beneficial microbes. Adding good quality compost before planting turf, annuals, perennials, trees and shrubs brings life to the soil and feeds existing soil organisms. Compost is effective in improving problem soils-in particular those that are compacted, heavy clay or sandy, poor in nutrients, or lead contaminated. It can improve structure, aerations and water holding capacity. You and your clients may see both long and short-term benefits, including faster plant establishment, decreased fertilizer and pesticide use, and lower water bills. Amending the soil with compost is one of the most important practices for a healthy, thriving, Bay-Friendly landscape.

It is important to first assess the soil for physical and chemical problems. If organic matter is low, as it often is in Alameda County, add compost according to lab recommendations, or as follows:

• If topsoil has been removed and stored during building construction, mix 1 cubic yard of compost into 3-5 cubic yards of soil before re-spreading.
• If the topsoil has not been removed then sheet mulching (program as internal link to tip for success on sheet mulching) is an efficient means of adding compost & other organic matter while controlling weeds.
• For turf installations: Incorporate 1 - 2 inches (3 1/3 - 6 2/3 cubic yards) of compost into 1000 square feet. Mix it with the top 5-7 inches of soil.
• For preparing planting beds: Spread 2-4 inches of compost over the surface of the soil and incorporate it into the top 6-12 inches of the planting bed.
• Mixing compost into the backfill of a planting hole for trees and shrubs may not yield significant benefits. Some research indicates that young plants benefit more than mature plants. Some specialists also believe that amending backfill can create such a difference between the soil in the hole and the surrounding soil that the roots don't grow outwards - it is as if they are growing in a pot. It will depend on the nature of the soil into which you are planting. To prevent this problem, amend the entire bed or create planting holes that are no deeper than the root ball and a minimum of 3 times size of the transplant's root ball. Rough up the sides of the hole. Mix soil from the hole with compost at a rate of 1 part compost to 3-5 parts soil (by volume) and backfill. Make the hole shallower and create a mound in heavy clay soils.
• Consider the conditions under which the plant grows naturally. Some California natives require a less fertile soil and compost may not be necessary.
• Finally, quality compost is important. Be certain to specify and purchase for quality compost for use in your client's landscapes.

5. Grasscycle
Grass clippings have about 4% nitrogen in them. When they are left on the lawn, they can meet some of the lawns' nitrogen needs, as well as supply an array of other nutrients. Grasscycling can reduce fertilizer requirements by as much as 50%, thereby lowering your costs and protecting water quality.

Learn more about grasscycling by ordering or downloading a copy of any of these publications:

• "A Landscaper's Guide to Grasscycling"
• "Una Guia del Jardinero para Reciclar Pasto"
• "A Case Study: Grasscycling"

6. Mulch regularly

Mulch is any material spread evenly over the surface of the soil. Organic materials, including chipped landscape debris, are preferable over inorganic materials because they supply nutrients over time. Nitrogen "drag" is usually not a problem, even when woody materials are used.

Mulching conserves water, enhances the growth of plants and the appearance of the landscape. It can also simplify your operations-thereby lowering your costs-by suppressing annual weed growth and reducing the need for trimming around trees and poles.

A variety of mulch types and techniques exist. Considering function, aesthetics and labor will help you decide the best way to successfully use mulch in your clients' landscapes. For example, sheet mulching is one technique of mulching that involves layering cardboard with compost and mulch to create a weed barrier. Local sources of compost can be found in the "Green Building and Bay-Friendly Materials" database.

Learn more about mulching by ordering or downloading a copy of any of these publications:

• "A Landscaper's Guide to Mulch"
• "A Case Study: Mulching"

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We’ll tolerate a little leaf debris in the beds, as long as it isn’t impeding plant health. Resource-efficient landscaping is healthy landscaping.”
-- Nate Silin, Owner, New Grow thLandscape, Oakland

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7. Aerate compacted soils
Turf on heavy soils and those subject to lots of use become compacted, which can increase their susceptibility to weeds, drought, disease & insect damage. Aerating and then topdressing with compost relieves compaction, stimulates root growth and disease resistance.

8. Feed soils naturally with compost topdressing or tea
There are important benefits to regularly adding a thin layer of good compost to the surface of the soil under turf, perennials, shrubs or trees, or drenching the soil with compost tea. A strong soil foodweb, which makes nutrients available to the plants and protects water quality, is nurtured when fed with compost.

9. Avoid synthetic, quick release fertilizers
Synthetic, quick release fertilizers frequently wash through the soil before they are even taken up by the plans. They can also damage soil microbial populations or cause a flush of tender new plant growth that is very attractive to sucking insects. Furthermore, many well-chosen California native plants thrive without fertilizers. Most other plants do not need the quick release fertilizers that are often applied on a scheduled basis. Their nutrient requirements can be met with compost, naturally derived fertilizers or slow-release synthetic fertilizers as a last resort. Slow release fertilizers make nutrients available when they are needed and are thus often a better value. Avoiding the use of synthetic, quick release fertilizers is an important part of protecting water quality and conserving resources.

10. Minimize the use of chemical pesticides
Many pesticides are toxic to microbes and other soil dwelling creatures such as earthworms: these toxins can reduce the diversity of soil life, select for resistant organisms or even increase soil pathogen density.

Minimizing pesticides reduces water pollution and helps support soil life, which cycles nutrients and promotes resistance to plant disease. Your costs may then be reduced in the long run.



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