Getting to Know Your Garden’s Soil: The Living Soil Ecosystem and Tilth

Last month (December 2012) we discussed methods for modifying soil drainage.  We end our soil series by considering the soil as a functioning ecosystem, with  implications for the home gardener.

Many gardeners focus on inorganic soil particles.  We ourselves spent most of a blog post (October, 2012) talking about soil particles and their effect on soil drainage.  But the inorganic (mineral) particles are just part of the story.   In fact, soils have four equally important components:

·         the mineral particles (sand, silt and clay)

·         air

·         water

·         organic material (living organisms and decomposing matter)

 

A soil in good condition for growing crops, garden vegetables and other plants is said to have ‘good tilth’.  It has the proper soil structure and nutrients to support healthy plant growth.  Good farmers and gardeners aspire to have soil with good tilth.

A soil with good tilth has a proper balance of mineral particles, air, water and organic material.  It smells good – not sour or rotten.   Often it will crumble easily in the hand.   It contains decomposing matter (humus) derived from mulch, dead leaves/branches and old roots. And it supports a wide range of life from gophers and earthworms to microscopic organisms – the soil biota.

 

Credit: USDA-NRCS

 

The soil is, in fact, a living ecosystem, complete with carnivores (meat eaters), plant eaters (herbivores), decomposers and parasites.  What many people assume is ‘just mineral soil’ is a whole world of living creatures.  The air, water and mineral components of soil provide food, living sites and other requirements for life.  Plants are just one part – albeit and important one - of this ecosystem.

In nature, soil organisms perform many important tasks. For example, earthworms burrow into the soil, loosening it and making it more porous.  This helps water to infiltrate and makes it easier for plant roots to grow. When we ‘loosen’ the soil before planting, we do what earthworms do in natural soil ecosystems.  If we ‘double dig’ a vegetable garden, we mimic the effects of energetic gophers at work in our garden.   How much easier – and more in tune with natural cycles – to encourage soil organisms to do the tasks they were meant to do.

Soil organisms perform a number of services, including some we cannot do for ourselves.   These services include:

• loosening the soil, decreasing soil compaction
• building complex soil structure that both drains and holds water
• increasing soil nutrient levels in the root zone of plants
• producing root-stimulating hormones
• ‘fixing’ nitrogen into a form that can be used by plants (and humans)
• competing with – and combating – destructive soil bacteria and fungi
• decomposing dead organic matter into humus

It’s time we take seriously the health of our garden soil biota and its effect on garden plants.  Fortunately, recent research suggests several things you can do to promote soil health. 

Soil tilth is affected by many factors including soil compaction, how much we dig/turn the soil, the fertilizers and other products we apply and physical factors like rainfall and temperature.  But perhaps the most important factor is the organic part: the humus and the living organisms.   According to soil science research [1]  ‘An acre of living soil can contain 900 pounds of earthworms, 2400 pounds of fungi, 1500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of arthropods and algae, and even small mammals in some cases.’    That’s a whole lot of living going on beneath the ground! 

How do you know if your soil supports life?  The best way is to look.   Dig up a scoop of soil, spread it out on a sheet of paper and look at it with a magnifying glass.   Here are some of the organisms you might find in a healthy soil:

Earthworms: 5-30 in a cubic foot of garden soil; expect at least 1 in your sample

Soil Arthropods (insects, mites, spiders, springtails, & millipedes) : 100-300 per cubic ft – you should see some small Arthropods in your sample.

Fungi (evidence of fungal strands or hyphae): may be present

Nematodes (non-segmented round worms): may be present

Several types of soil organisms will be too small for you to see.   Individual species of many of these microscopic soil organisms have not yet even been described and named.  Microscopic soil organisms include:

          Bacteria

          Protozoa

          Viruses

          Others

We’ve included several good references at the end of this post.  They provide more details on soil organisms and their roles.  We hope you’ll want to learn more!

If your garden is new, you may not have seen many organisms in your scoop of soil.  This should not alarm you – the numbers and types of soil organisms tend to increase as a garden matures. Soil building takes time.  But there are several good, scientifically-based management practices that can make your soil more hospitable to soil organisms.   We suggest you follow these practices to increase your soil tilth.

1. Add organic matter (compost) to the vegetable garden.  This provides food for many soil decomposers.  The humus produced will increase soil structure and fertility.  If gardening with California native plants, be sure that your plants do not require a ‘nutrient-poor soil’ before adding organic material.  See our November 2012 post on ‘Soil Amendments’.
2. Use mulch (if appropriate).  Mulches help keep soil moisture and temperature even, providing better habitat.  Organic mulches break down, supplying organic food for decomposers. Be sure to use the correct type of mulch, particularly if gardening with California native and other water-wise plants (see our posting on Mulches – July 2012).
3. Water appropriately.  The lives of native soil organisms are tied to the moisture cycles that occur in nature.   In our local gardens, soil organisms ‘expect’ adequate soil moisture from late fall through spring.  But they are adapted to periods of drought in summer and fall.   Plant native plants – and water them appropriately – and you’ll supply the water regimen local soil organisms need.   We’ll provide more advice about soil moisture and irrigation this spring.
4. Plant native plants.  Plants and soil organisms have complex relationships that are not entirely understood.  The more native plants you include in your garden, the better the habitat for native soil organisms. Choose plants that are native to your area and reap the benefits in healthy soil.
5. Avoid unnecessary digging, turning or tilling of soil.  All of these effect soil structure and adversely affect soil habitat.   The best soil for soil organisms is one that’s simply left alone.
6. Prevent soil compaction.  Soil compaction decreases soil pores and the water and air they contain.  Provide walkways in the garden to limit compaction.  Avoid walking on clay soils when wet.
7. Limit use of pesticides.   Many kill beneficial organisms along with the pests.   And beneficial soil organisms often eat pest organisms for food.
8. Limit use of fertilizers.  These amendments change the chemical environment of the soil.   Research has shown that over-use of fertilizers actually decreases soil biota in many soils.    Southern California gardeners in particular should use chemical fertilizers with care.
9. Plant a variety of plants (diversify); rotate plants in the vegetable garden.  Planting a variety of plants insures that soil organisms obtain the nutrients and other materials needed for life.  It also provides insurance against the effects of soil pests and diseases.   Rotating vegetable crops helps prevent the buildup of unwanted soil organisms.
10.  Respect your soil as a complex ecosystem.  Remember that your soil supports a living system every bit as complex as above-ground ecosystems.

Building up a range of soil organisms takes time, patience and working with Mother Nature.  But the benefits to your garden include increased plant health, less time spent on gardening tasks and the conservation of important soil organisms.   We hope you’ll choose to support life – including life that you cannot see - in your garden.

__________________________________________________________

 

Learn more about soil tilth and soil organisms at:

 

http://www.cmg.colostate.edu/gardennotes/212.html

 

http://soils.usda.gov/sqi/

 

http://www.ag.auburn.edu/auxiliary/nsdl/scasc/Proceedings/1990/Karlen.pdf

http://www.enviroliteracy.org/article.php/700.html

 

http://www.safs.msu.edu/soilecology/soilbiology.htm#

 

http://www.ecoversity.org/archives/soil_ecology.pdf

http://www.extension.umn.edu/distribution/cropsystems/components/7403_02.html

http://www.soilhealth.com/soils-are-alive/

  

 

 

References

 

1.   Pimentel, D. et al. 1995. Environmental and economic costs of soil erosion and conservation benefits. Science. Vol. 267, No. 24. p. 1117-1122.

         

Getting to Know Your Garden’s Soil: Improving Soil Drainage

Over the past few months we’ve discussed urban soils (September 2012), soil testing (October 2012) and soil amendments (November 2012).  We end the year by considering soil drainage.  Next month we’ll present one final soils topic - the soil as a living, productive ecosystem.

If you’ve done a soil perc test you now know whether your soil drains quickly, slowly or somewhere in between.   Depending on your results, you may decide to  select appropriate plants based on their drainage needs.  Alternatively, you may choose to alter the drainage of parts of your garden. As always, your gardening choices are unique to your own situation. Our goal at Mother Nature’s Backyard is to help you make informed choices.

 

 

Image courtesy of http://www.salinitymanagement.org/
Salinity%20Management%20Guide/ds/ds_7.html

 

Soil drainage is determined by pore spaces.  Soil pores are spaces that are filled with either air or water (see picture above).  Most soils have a combination of large and small pore spaces.  Under normal conditions, larger pores are filled with air and smaller pores with water.  This is good because plant roots and most soil organisms need ready access to both air (oxygen) and water.

Being composed of relatively large soil particles, sandy soils have more large and fewer small pores than soils with more silt and clay particles. The abundant large pores fill quickly, allowing sandy soils to take up water more easily than clay soils.  On the flip side, large pores don’t retain water as well, so sandy soils also dry out more quickly.  

Soils that drain quickly present several challenges.  First, they require more frequent watering, particularly during hot, windy weather.  These soils also leach out soil nutrients more quickly.  Nutrient leaching occurs for two reasons: 1) water percolates through sandy soils more quickly, taking with it dissolved minerals and 2) clay, silt and humus (organic) particles attract soil minerals (via a small electro-magnetic charge) and hold them better than do sand particles. 

As a result of leaching, sandy soils may have lower levels of key nutrients like nitrogen, phosphorus and iron.   Growing plants with high nutrient requirements (like many vegetables and citrus trees) in sandy soils requires routine application of fertilizers or compost.   Fortunately, many Southern California native plants have low nutrient needs and are well-suited to sandy or rocky soils, even without fertilization.   For a list of native plants suitable for sandy soils see: http://www.nbs.csudh.edu/biology/projectsound/habitat/documents/Sandy_Soils-3-11.pdf

On the positive side, very well drained soils hardly ever become saturated (water-logged).  Clay and silty soils have fewer large pore spaces (and more small pores), so they take up water more slowly – but retain soil moisture longer.  These soils also have positive and negative characteristics with regards to drainage.

Slowly draining soils require less irrigation and retain nutrients better.  But they have the potential to become water-logged during wet winters or with over-watering.  Water-logged soils deprive roots of oxygen; plants growing on wet soils tend to be shallow rooted.  Prolonged exposure to water-logged soils can be hazardous to plant health and even lead to death.  Plants that need well-drained soils – including many California native plants – are particularly vulnerable.  These plants often do well in clay soils until their first El Niño year, when they suddenly yellow and die.   They’ve literally ‘drowned’ in the water saturated soil.

On the other hand, slowly draining soils are perfect for a wide range of interesting native plants.  These include plants that normally grow around lakes or streams as well as those from our local seasonal (vernal) marshes and vernal pools (see                http://www.nbs.csudh.edu/biology/projectsound/habitat/documents/Clay_Soils-3-11.pdf and http://www.nbs.csudh.edu/biology/projectsound/habitat/documents/Riparian_Palette-3-11.pdf ).  If you have a slow-draining soil, consider yourself lucky!  People with quickly draining soils can only grow such plants in containers

 

 

  

Compacted soils can be a challenge in local gardens.  Compacted soils (see above) often lack sufficient large pores.  This explains several characteristics of compacted soils.  First, they tend to be low in oxygen compared to non-compacted soils.  This usually only becomes a problem during periods of prolonged heavy rains or when compacted soils are over-watered.   Compacted soils also tend have slow water uptake, leading to runoff.  If you have badly compacted soils – or have a hardpan layer beneath the topsoil - you may want to try one of the methods suggested below.

Our approach to gardening at Mother Nature’s Backyard emphasizes respecting the forces of nature and working with existing conditions.  We’ve come to that philosophy in part for scientific reasons;  we believe it’s important to conserve and restore natural landscapes for their beauty, habitat value and sense of place.   But we’re also pragmatic.  It’s often easier to work with what you have – by choosing appropriate plants and watering methods – than to change your soil dramatically.  That being said, there are a few, relatively simple things you can do that will allow you to grow plants that normally require soils that have faster (or slower) drainage than your garden’s soil.

 

Garden in Raised Beds, Containers & Planters

One of the easiest ways to provide soil with specific characteristics is to garden in raised beds, containers and planters.  These contained environments allow you to create exactly the right soil mix.  You can create soils with better drainage if you want to grow cacti or plants that require sandy or rocky soils. You can provide slowly draining soils for marsh or bog plants.  Or you can create a light, well-drained mix with high organic and nutrient content for growing garden vegetables.  

Container gardening is fun and can be done in almost any garden.  There are a few tricks to gardening in containers and raised beds.  Fortunately, there are many good books and internet resources to get you started.

 

Create Micro-berms to Increase Soil Drainage

 Another trick for creating faster drainage is to use small soil berms.  A berm is simply a mound of earth. In the garden, berms are usually planted.   Berms need not be massive or require heavy earthmoving equipment to create.  You can make them with a little effort and a hand shovel in most soils.    

 

Central berm before planting (view looking south).  Note gentle slope.

Micro-berms are 1-2 feet taller than the surrounding soil and of any size or shape.  In general, rounded curved shapes with gently sloping sides are most attractive. The photo above shows our central berm in Mother Nature’s Backyard.  It’s about 20 feet across and gently curved in shape.  The central berm is about 2 ½ feet taller than the rest of the garden at its highest point and slopes gently down to the north and east.  We grow local Salvias (Sages), California Sagebrush, native Buckwheats and Penstemons on our central berm.  These plants like good drainage and we have clay-loam soil with moderate drainage.   We provide better drainage with our central berm.   The plants that need the best drainage are planted at the top.

 

Central berm as it looks today - view looking west

 

Micro-berms needn’t be large.  Below is a photo of our small ‘Salvia Berm’ which looks more like a pitcher’s mound than a large berm.  Our ‘Salvia berm’ is only about 1 ft. tall and perhaps 6 feet across. When the plants mature you won’t even know it’s there.
 

The small 'Salvia Berm' is circled

 

If your soil drains slowly, you may be tempted to create micro-berms using imported topsoil.  Imported soils may improve drainage and often can be delivered (and dumped) in place in your garden.    But you’ll need to insure that the better-draining imported soil doesn’t just sit atop the slower-draining native soil, creating an impermeable layer.

When creating a berm with imported soil, mix some of the imported and native soils and create a mixed-soil layer between the berm and native soil.  Ideally, this layer should be at least 12 inches deep, though even 6 inches will be of benefit.  If you cannot create a mixed layer, at the very least you should break up the top layer of native soil before creating your berm.  Taking these steps – or using soil that is the same or similar to the native soil – will insure that your berm drains properly.

 

Create Small Depressions to Increase Water Retention

You can also increase the water-holding capacity of a soil by creating shallow depressions where water can collect.  This is particularly helpful in well-drained soils.  Such depressions are sometimes called swales,  although  true drainage swales and rain gardens require a little more thought and engineering.  Simple depressions don’t have to be deep – several inches below the rest of the garden will do.  Be sure to gently slope the sides so you don’t create a safety hazard.  Then  grow plants that need a little more water in these depressions.

 

Add Organic Materials (unless the plants need nutrient-poor soils)

Consider adding compost to your vegetable garden or non-native flower beds.  Compost adds nutrients while increasing the soil’s ability to hold water.  Organic particles (humus) create small soil pores and also decrease the leaching of nutrients.   They are a normal part of most mature soils.    Even organic mulches (see July, 2012 posting) contribute organic materials to the soil as they break down.  At least a 1 percent increase in organic matter is required to have an effect on the water- and nutrient-holding capacity of a soil.

 

Drill Holes Through a Hardpan Layer

If you have a clay or hardpan layer, you may want to consider drilling holes through it.   First test your soil to be sure that a hard, compacted or impermeable layer is the cause of your drainage problems (see October 2012 posting on ‘Testing Your Soil’).  This will also indicate the location and depth of the compacted layer.   Use a soil auger to drill a series of holes through the hardpan.  See the following for more: http://ceventura.ucanr.edu/Gardening/Coastal/Landscape_578/Hardpan/ .

 

 

Frequently Asked Questions

 

Do I need to change my soil’s drainage properties?   No.  If you have a well-drained soil,  no action is needed.  If your soil drains quickly or slowly, you can select plants appropriate for your sandy or clay soil.   Most local soils support a wide range of native and non-native plants. 

 

Should I rototill or double-dig my garden before planting to improve drainage?    In most cases, the answer is no.  While these methods have long been used for intensive vegetable gardening, they may actually do more harm than good for many local soils.  We’ll discuss this more in our January 2013 posting. These methods also bring up buried weed seeds. 

 

Can I improve drainage with ‘lasagna gardening’?  ‘Lasagna gardening’ involves double-digging then layering cardboard/newspaper strips and green materials that decompose over time.  The method is sometimes recommended for gardens with thin/no topsoil – usually in places with far more precipitation than we get.   The ‘lasagna’ method does not improve drainage in most local soils – in fact it may decrease it.  Like any double-digging method, it also destroys the natural soil layers that build up over time.  We don’t recommend this method.  See https://sharepoint.cahnrs.wsu.edu/blogs/urbanhort/archive/2011/03/30/is-quote-lasagna-gardening-quote-really-worth-the-effort.aspx for more.

Do I need to ‘loosen’ my soil every year?   Once again, the answer is usually no.   Soil around trees, shrubs and other permanent plantings is better off left alone.  Use a layer of mulch if appropriate, but don’t dig to improve drainage.   You may want to loosen the soil in your vegetable garden or garden beds containing non-native flowers that are routinely replaced.    Adding compost will also help to improve drainage in soils that are used intensively.

 

Additional Resources

 

http://www.cmg.colostate.edu/gardennotes/219.html

 

http://goodlifegarden.ucdavis.edu/blog/2011/08/how-to-improve-your-soil-drainage/

 

http://www.cmg.colostate.edu/gardennotes/213.html

 

Send your garden soils questions to mothernaturesbackyard10@gmail.com  or post a comment below.

 

 

 

 



Getting to Know Your Garden’s Soil: Soil Amendments

 

The physical properties of soil - including soil composition, drainage properties, pH and fertility - all affect your ability to grow plants.   So it’s important to learn about them early in the process of planning your garden.

Last month (October, 2012) we discussed several simple soil tests for determining the physical characteristics of your soil.  If you’ve done these tests, you now know whether your soil drains quickly, slowly or somewhere in between.   But how can you use this knowledge to improve your gardening success?

In the past, California gardeners were encouraged to amend their soils prior to planting.  If your soil was slightly basic/alkali (pH 7.5-8.0 – common in our area) and you wanted to plant an acid-loving plant like an Azalea, you were advised to amend the soil with peat moss and use an acid fertilizer.  If your soil was sandy, you were encouraged to add organic amendments like steer manure and compost to ‘improve’ your soil.   And so on and so forth.

The Colorado State University Extension (see suggested references, below) defines soil amendments as follows:

A soil amendment is any material added to a soil to improve its physical properties, such as water retention, permeability, water infiltration, drainage, aeration and structure. The goal is to provide a better environment for roots.

To do its work, an amendment must be thoroughly mixed into the soil. If it is merely buried, its effectiveness is reduced, and it will interfere with water and air movement and root growth.

 

A visit to the local gardening center can be a confusing experience; there are so many different soil amendment products available! All of them cost money and require time and effort to use.   So, what’s a sensible approach to soil amendments and fertilizers?

Here at Mother Nature’s Backyard, we like to garden in concert with Mother Nature.  We suggest working with what you have rather than trying to change it.  Consider your soil’s characteristics as assets, rather than properties that automatically need improvement.  And tailor your plant choices and irrigation practices to your un-amended soil.   

This approach runs counter to the advice of many traditional gardeners, but we think it has merit.  For one thing, you’ll save money and time.  You won’t be overusing products that can contaminate the soil and ground water.  You’ll also learn about a whole new set of plants – California natives for the most part – that may have grown in your soil for thousands of years.   And you’ll have the satisfaction of seeing your garden grow into a small functioning ecosystem, above ground and below.

 

Do I have to use soil amendments?

The simple answer is no.  The plants that do best in a garden are usually those suited to the natural soil conditions. As it turns out, it’s actually difficult and expensive to change some of the basic soil properties, like pH, using soil amendments.   In the long run, it’s usually easier to plant the right plants for the soil conditions rather than the other way around.

Many gardeners don’t realize that a large number of California native plants  thrive in local sandy and clay soils.  These include everything from annual wildflowers and native grasses to groundcovers, shrubs and trees.  For lists of plants particularly suited to sandy and clay soils in our area see:

·         Sandy Soils List: http://www.nbs.csudh.edu/biology/projectsound/habitat/documents/Sandy_Soils-3-11.pdf   and a talk on gardening in sandy soils:

http://www.slideshare.net/cvadheim/gardening-on-sand-2009a

·         Clay Soils List: http://www.nbs.csudh.edu/biology/projectsound/habitat/documents/Clay_Soils-3-11.pdf and a talk about gardening in clay soils: http://www.slideshare.net/cvadheim/clay-hummingbirds-2009

 

Can I amend just part of my garden?

Yes – in fact that’s often a good idea.  With a little planning, you can amend only areas that really need it and plant better suited plants in the rest of the garden.   By grouping plants (like vegetables) in one area you can save effort while still giving each plant the soil conditions it needs.

 

What if I want to grow a plant with very different needs than my soil provides?

If possible, consider growing the plant in a large container.  It’s easy to give plants the specialized soils they need in containers.   Another possibility is to grow the plant in a planter or in raised beds.   Once again, the idea is to group plants with similar needs so you amend only a portion of your total garden.

 

Should I amend my vegetable garden's soil?

Yes. The vegetable garden has soil requirements that are often different from the rest of the garden.  Vegetables need a well-drained soil with relatively high nutrient levels.  The best way to provide this is to amend vegetable garden soils with compost and supplemental fertilizer. If you have a vegetable garden you will likely want to amend it yearly.

Consider growing vegetable in raised beds or containers which can be amended more easily.   For some great resources on vegetable gardening see: http://celosangeles.ucdavis.edu/Common_Ground_Garden_Program/Gardening_Articles/

 

Should I amend soils in containers?

The environment in containers (pots/planters) is quite different from that in the ground.  Drainage and soil nutrients are particular issues.  We suggest using a good potting mix (rather than garden soil) in containers.  Garden soil usually doesn’t drain as well as potting mix and may contain undesirable soil organisms.  You can amend the potting mix to suit the needs to the plant: more sandy, more acidic, higher nutrient levels, etc.   

Pots, planters and containers usually benefit from occasional to yearly addition of soil amendments or even an entire change of soil.   We’ll discuss container gardening in more detail in another post.

 

My soil drains slowly.  Shouldn’t I amend it to improve drainage?

Not necessarily.  Clay and clay-loam soils do drain more slowly.  But they also retain soil moisture, so you don’t need to water as often in the summer and fall. We know from experience in Mother Nature’s Backyard!

There are plenty of plants that like clay soils, so you can tailor your plant choice to your soil drainage characteristics.  And there are other things you can do to improve soil drainage.  We’ll discuss these in some detail next month (December, 2012 – Improving Soil Drainage).

 

How do soil amendments differ from mulches?

Soil amendments are incorporated into the soil before planting, while mulches are spread on top of it (see July, 2012 for a discussion of Mulches).  Organic mulches do decompose and change a soil’s characteristics over time.  But they are not soil amendments.

 

Should I amend soil in the potting hole before I plant a tree/shrub?

Not a good idea – for native and non-native plants alike.  Research has shown that this old practice actually inhibits the development of a good root system.  The following site debunks this and other common horticultural myths (and is fun, informational reading): http://www.puyallup.wsu.edu/~Linda%20Chalker-Scott/Horticultural%20Myths_files/index.html

 

What are common soil amendments?

Like mulches, soil amendments are inorganic (either mined or man-made) or organic (from something living).   The table below summarizes  characteristics of the most common soil amendments used in S. California gardens.

 

Amendment	Uses and Cautions
Sand	Why used: once believed to improve drainage – usually does not Best uses: for cacti grown in containers (mixed with potting soil to create a ‘cactus mix’) Cautions: never use in clay soils; will create ‘concrete’
Perlite	Why used: to improve drainage Best uses: In containers; in potting mix for raising plants from cuttings or seedlings (need a well-drained potting mix) Cautions: costly
Vermiculite	Why used: to improve water retention Best uses: In containers; in potting mix for raising plants from cuttings or seedlings (need moist soil) Cautions: costly; becoming hard to find
Soil acidifiers (Sulphur)	Why used: to decrease soil pH Best uses: For acid-loving plants grown in containers; Cautions: difficult to decrease soil pH; need to continue treatment over time
Wood products   (bark, wood chips, hulls, etc.)	Why used: to improve drainage and soil fertility Best uses: as mulch (rather than soil amendment); in compost (where it adds nutrients) Cautions:  the breakdown of wood products requires high levels of soil Nitrogen – need to add N fertilizer for 3-4 years after use;  breakdown may release natural chemicals (tannins) which inhibit seed germination.
Peat/Sphagnum Moss	Why used: to decrease soil pH and improve water retention Best uses: in containers or planters where acid-loving plants are grown Cautions: decreases soil fertility and drainage over time; environmental concerns over mining of peat bogs
Grass clippings/ chopped leaves	Why used: to improve soil fertility Best uses: to produce compost; chopped leaves for mulch Cautions: may contain weed seeds
Manure (aged)	Why used: to improve soil drainage or water retention; to improve soil fertility. Best uses: vegetable garden Cautions: increases soil salts - can make soils toxic to some plants & soil organisms; will ‘burn’ plants if not well aged
Compost (home composted)	Why used: to improve drainage and soil fertility Best uses: vegetable garden; rose garden; areas with non-native plants (for example, a traditional flower bed) Cautions:  may increase soil nutrients too much for local native plants.
Commercial Compost/ Amendment Blends	Why used: to improve drainage and soil fertility Best uses: containers; houseplants Cautions: often expensive; not needed/can be too ‘rich’ for many native plants
Worm Castings	Why used: improve soil fertility and raise pH Best uses: containers; houseplants Cautions: expensive if purchased; you can raise earthworms & create your own, but that takes space, effort.
Fertilizers   (‘chemical’ or ‘natural’)	Why used: to improve soil fertility Best uses: vegetable garden; containers; rose garden; flower garden (non-native plants); native plants from wetlands or ponds/stream banks (1/4 recommended dose) Cautions: most native plants need none (or low doses); for all plants, over-use of fertilizer can lead to excessive growth & decreased plant health/increased pests; long-term use of fertilizers can actually make soils toxic to plants and beneficial soil organisms.   Use only as needed.

 

 

Learn more about soil amendments at:

 

·         http://www.ext.colostate.edu/pubs/garden/07235.html

·       http://celosangeles.ucanr.edu/Common_Ground_Garden_Program/Gardening_Articles/  (Los Angeles Co. Master Gardener publications)

·         http://www.commongroundinpaloalto.org/fertilizers.htm#boxedandbaggedfertilizers (vegetable garden)

 

 

You can e-mail your Amendment and  Garden Soil questions to: mothernaturesbackyard10@gmail.com