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Compost vs Mulch, What’s the Difference?

Sometimes, as anyone learning a new language can tell you, even words that have different dictionary meanings can take on new meanings. For gardeners the terms compost and mulch are two terms that are sometimes used interchangeably.. The difference between the compost and mulch can be quite confusing, especially for the novice gardener, since their uses can overlap. Yet, for the sake of your plant’s and soil’s health, there are differences.

Technically speaking, compost is organic matter that has been decomposed, while mulch is a layer of organic or inorganic matter placed on top of the soil as a protective cover. A commenter, RobertZ6, on gardenweb.com defined compost as a ‘What’, while mulch is a ‘Where.’

So what are some of the main functions of the two and how do they differ:

Compost: Compost is a biologically active material resulting from decomposition of organic matter. Bacteria, fungi, soil insects and others help with this decomposition. In general, there are two different methods of making compost: 1) the “fast” method consisting of the ratio of two parts brown/dry material to one part green/juicy material, plus moisture, plus aeration/turning the pile; and 2) the “slow” method where leaves, grass, vegetable refuse, etc. are allowed to build up in a pile and slowly over time decomposition takes place and compost results.

Jane and Cindy at Work Making Compost-Fast Method!

Jane and Cindy at Work Making Compost-Fast Method!

Compost is often considered to be a soil conditioner, rather than a fertilizer since the actually nutrient value of compost can be so variable. Though the fertilizing component of compost is small, www.planetnatural.com says that “compost can aid plants in many ways quite independent of its nutrient content. Because it improves soil structure, adds beneficial microbes, and boosts cation exchange capacity (CEC), compost improves the mobility of air, water and nutrients in the soil, all of which make nutrients more readily available to plants.” Compost that is fully decomposed/”finished” is called humus. It is dark brown, crumbly, with no distinguishable features, and has a sweet, pleasant smell.

Mulch: Mulch can be either organic or inorganic and is spread over the top of the soil to cover it. Examples of organic mulch include leaves, straw, and wood chips. Inorganic mulches include rubber, gravel, and landscape fabric. The purposes of mulch include suppressing weeds, moderating soil temperature, conserving water, maintaining a porous surface, and helping to prevent erosion. The use of organic mulch can improve the soil structure as it gradually decomposes over time.

Chopped Up Native Tree Trimmings and Leaves Can Be Used as Mulch

Chopped Up Native Tree Trimmings and Leaves Can Be Used as Mulch

So… where does the confusion in terms and usage for some gardeners lie? Two main questions come to mind:

1) Can compost can be used as mulch?   The answer to this question is “yes.” It is possible to add a layer of only compost to the top of the soil and use it as mulch. In fact, in the case of using organic mulch such as wood chips in a bed, the layer of wood chips closest to the soil will gradually break down into compost over time. Eventually it will be necessary to add more mulch to a bed or mulched pathway to account for this. One of the Master Gardeners says that she uses her unfinished, not completely decomposed, compost as mulch in her beds. Placing a 1-3 inch layer of this unfinished compost on top of the soil as mulch would enable the mulch to break down quicker into compost. Earthworms will gradually move the finished compost down into the soil.

Many gardeners however never have enough finished (or even unfinished) compost to use pure compost as mulch on top of the soil. Plus the cost of purchasing bags of compost to do this would be prohibitive for many. Therefore most gardeners choose to work their finished compost into the soil and top dress the soil with mulch.

2) Can mulch (for example shredded wood chips) be tilled into the soil? The answer to this is both yes and no.

No: Though it might seem as if this would “cut out the middle man” (i.e. the need to make finished compost), in general it is usually not recommended to incorporate shredded wood chips, or even un-composted leaves, into your soil.

To understand why, it is necessary to know a little about the way that decomposition of organic matter takes place and also the nutrients that plants need. To grossly over-simplify a very complex subject, plants need three primary nutrients (nitrogen (N), phosphorus (P), and potassium (K) plus thirteen secondary and micronutrients nutrients such as magnesium (Mg) and iron (Fe) to grow well. Most soils contain at least some of these nutrients. However many soils in Dallas County have a deficiency in nitrogen. A soil test can confirm whether this is true on your property.

This deficit of nitrogen in many Dallas County soils is important because in order to decompose organic material, the bacteria and fungi, which are the first organisms responsible for decomposition, also need nitrogen to feed on in order to live. When a large amount of un-decomposed material, such as wood chips, is incorporated into the soil, there is an increase in the number of bacteria and fungi needed to break it down. Since the bacteria and fungi need nitrogen as part of their diet, these microbes will start using up what is present in the soil. Since Dallas County soils are often deficit in nitrogen, sometimes not enough nitrogen is left in the soil to feed both this increase in soil microbes and the plants. This in turn can leave plants starved of nitrogen, one of their essential nutrients. Plants that are nitrogen deficient often have pale green or yellow leaves and exhibit poor growth.

              Yes: On the other hand, it is possible that the answer to the question of whether mulch can be tilled into the soil, can be answered “yes.” Though not generally recommended, one can till in mulch, even shredded wood chips or live oak leaves which do not readily decompose, into the soil if certain factors (time and/or supplemental nitrogen) are taken into consideration:

Time: If enough time is available to let a bed lie fallow/unplanted for a season or even one or two years, over time the mulch will gradually decompose into compost.  This can be compared to the “slow” method of making compost.

Supplemental nitrogen: An article in www.motherearthnews.com states that in an apple orchard, it was found that “a high-fiber diet of wood materials is exactly what many soils need. Rotted bits of wood persist as organic matter for a long time, enhancing the soil’s ability to retain nutrients and moisture, which results in bigger, better crops.” However a very high nitrogen source, in that case blood meal, 12-0-0, was also added at the same time as the apple trees were planted. The addition of supplemental nitrogen offset the bacteria’s and fungi’s taking it from the soil and provided nitrogen to the plants.

There is an ancient gardening technique called hugelkultur (which in German means “mound culture”) that makes use of using woody material, even logs, to make beds. According to those who use this technique, these raised beds retain moisture (supposedly needing only very infrequent watering,) improve soil fertility, and improve drainage. In this technique a mound of logs and twigs is built up, and finished compost, manure, kitchen scraps, etc. are packed into the spaces between the woody materials. A layer of top soil is placed on top of the mound and planted. There are several articles and videos on the web showing how to construct a hugelkultur bed.

A few years ago, several community gardens and individuals became interested in trying hugelkultur in the Dallas area. If you know of someone who has tried it, please share their results. We gardeners all learn from one another.

Though most of this article presents an extremely over-simplified explanation of the differences between compost and mulch and why it is important for your plant’s and soil’s health, hopefully the reasoning behind what is taking place will help you to understand the difference and help you grow the healthiest plants possible.

Carolyn

Pictures by Starla

 

 

 

Beginnings

The dirt’s flying at the new Rainctcher’s Garden-into the new raised vegetable beds on the north field.

Straight rows of onions stand like little soldiers, the first vegetables planted at the new garden. We planted one bunch each of 1015y (yellow) and Southern Belle Red (red). Potatoes are next!

 Our First Onions Planted at The Raincatcher's Garden!

Our First Onions Planted at The Raincatcher’s Garden!

The top 12 inches of the beds have been filled with a generous gift of Vegetable Garden Mix from Living Earth Technology, made of compost, sandy loam, aged mulch, and other ingredients.  We topped it off with some of our homemade compost.

Living Earth, Sarah, and Judy!

Living Earth, Sarah, Tim, and Judy!

Last week the first of our trees, an urban forest demonstration was planted. Expect to see more about berm building and tree planting next week.

Ginko Tree Planted February 19, 2015

Ginkgo Tree Planted February 19, 2015

Pictures by Starla

Writing taken from Jim and Elizabeth emails

Onion Peelings here.

Onion Recipe

Ann

 

 

Keyhole Gardening Review

Last week there was an article about Key Hole Gardening in the Dallas Morning News.  Read it  here.  In my opinion it did not elaborate enough on our beautiful efforts to teach Dallas County citizens about this garden survival method.

Annette teaching Keyhole Garden concepts.

Annette teaching Keyhole Garden concepts.

Our garden is located at 2311 Joe Field Road in Dallas, 75229. We share Dallas County property with the county’s Automovie Service Center and have been making gardens and teaching opportunities at this location since 2005.

Our aim is  to teach Dallas County residents sound horticultural practices combined with a heart for our natural resources.

We harvest rainwater to water our gardens and use drip irrigation.  Keyhole gardening uses less water and has naturally become a component of our education.

Another view of our Keyhole Garden

Another view of our Keyhole Garden

For an extensive education about Keyhole gardening, please review Annette’s writing on the subject.

As gardeners and stewards of our patch of dirt at 2311 Joe Field Road, we will always strive to present the less intrusive ways of gardening using the least amount of water and no pesticides.  Our gardens and our hearts thrive with this approach and through this blog and our classes, field trips and harvest to table presentations, we want to share what we have learned with you.

Thank goodness for the rain last week which filled out 2-2500 gallon rainwater harvesting tanks with water for our gardens!

Ann

One Way To Prepare A New Garden Bed

Dallas Garden Buzz wants to be the blog that helps you achieve the garden results we all long for in North Texas.  We don’t want to be just a pretty face but hope to guide you through the garden seasons with advice you can use to prepare and plan your own successful gardens.  From time to time, we may share experience from gardens other than The Demonstration Garden to illustrate gardening technique of lessons we have learned.

My Mom asked me to oversee the installation of a new garden patch at her house. I arrived early  just in time to see a plot of grass approximately 4 feet wide and 14 feet long being extracted.  The old grass went to the back part of the yard where grass had died out.

Mom's Yard "Before"

 Mom  wanted a  garden bed wide enough for flowers and a few tomatoes in the sunniest part of her yard.  She is also a Dallas County Master Gardener, so we agreed to use the Earth-Kind bed preparation for this new garden.  We have used this recipe for soil improvement at  The Demonstration Garden.

To coax the clay soil into submission for her dream garden, we added  3 inches of compost and 3 inches of expanded shale.  Picture the new garden bed as a cake, think about frosting it with a 3 inch layer of compost and a 3 inch layer of expanded shale. Now till it in so that you have changed the structure of the top 12 inches of soil in your garden.

Expanded Shale and Compost Blended Together

(To make the process easier, Dallasites can purchase a  blend of these two products  in bulk at places like Soil Building Systems and Living Earth Technology under the product names of Clay Slayer or  Clay Killer.)  Buy six inches of the product to till into your garden soil (3 inches of compost and 3 inches of expanded shale equals 6 inches of the two combined).

To figure the cubic yards needed we multiplied the 14 feet x 4 feet x .50 feet and divided by 27.  If you want to skip the math, use the cubic yard calculator on the Soil Building Systems website.  For Mom’s garden one yard of the blended product was purchased and tilled into the plot.

Rototilling Expanded Shale and Compost Into The New Garden Bed

Now that the clay has been amended into luscious, friable garden soil, the garden is ready for planting and will be topped off with 3 inches of mulch

Mom, your dream has come true!

Ann

Compost

Cindy With Mulching MowerCompost is recycled organic material.  Grass clippings, leaves and plant refuse, things  that used to be thrown into the landfill, are converted with the help of microbes, molds and insects into food for our garden.

WHAT DO YOU NEED TO MAKE COMPOST?

(4 components + tools)

 NITROGEN – GREEN – Grass clippings, Fruit & Vegetable Scraps, Coffee Grounds

CARBON – BROWN – Dried leaves, dried plants, shredded paper, wood chips (also known as mulch)

MOISTURE – BLUE – Water, leftover juices from drinks, pickle juice, jams, jelly, any liquid containing sugar

 OXYGEN – WHITE – Air/circulation

HOW DOES IT BECOME COMPOST?

Mix the above 4 ingredients and let nature take over.    All around us are small animals called MICROBES.  Like any animal, they like to eat.  Feed them and they multiply.  Their food is the materials we mixed together (green, brown) with the water.  The air/oxygen allows them to live. 

HOW SHOULD A COMPOST PILE LOOK?

Compost bins/piles can be as simple as a pile on the ground or as elaborate and a hand or machine cranked barrel.  MASS is more important in composting than its container. The deeper and wider the pile, the faster it will compost.  Good dimensions are 3’ deep and 3-4’ in diameter.  Piles can be square, rectangular, or round. 

Round Compost Bin The outside edge (as much as 12” can dry out fairly quickly so I prefer the round style—acts like an insulator.  The interior stays moist and heats up with microbial activity.  When the pile is turned, the dry outer material is stirred into the moist interior and helps to aerate the pile. Depending on your available space, it is nice to have more than one container so you can move the compost when turning it.  Three containers allow you to have compost at different stages of maturation; new, in-process, finished. 

WHAT IS COMPOST GOOD FOR?

1)             Feeding plants and soil animals (worms, insects, microbes)

2)            Rebuilding the soil by improving its friability  and fertility

3)            Improving the ability of the soil to absorb moisture, avoiding excess runoff and erosion

4)            Keeping organic materials out of our landfills

What we had to get from outside sources when we first began our garden, we are now able to produce in our COMPOST area.  Not only do we feed our many garden areas, but are also able to furnish our fellow gardeners with food for their gardens.

Cindy

Keyhole Gardening

Keyhole gardening is considered an “African survival strategy” in a land of scarce resources and unforgiving climate.  According to reports from the BBC, 3 keyhole gardens can feed an African family of 10 for an entire year. 

A humanitarian aid organization in southern Africa developed this particular sustainable gardening method.  The design originates in permaculture which is a branch of ecological design & engineering that develops sustainable human settlements & self-maintained agricultural systems modeled from natural ecosystems. 

          A keyhole garden is the “ultimate raised-bed planter.” It consists of a circular shape w/ a 6 foot diameter & stands about waist-high.  A notched-in section like a pie-shaped wedge allows access to the plants.  It can be constructed from local recycled materials & incorporates a central composting basket into which food scraps/organic wastes are placed.  The garden is also watered through this basket.  It uses far less water than conventional gardens & recycles as it grows.  From a birds-eye view this garden reminds one of a keyhole.  

Keyhole Garden Bird's Eye View and Side View

 Keyhole gardening is an adaptable concept & almost any kind of raised bed of about a 6 foot diameter can be converted.  The basic idea is functionality & efficiency: producing the most nutritious organic produce in the least amount of space using minimal water.  Cattle water troughs, tractor & truck tires, old bathtubs, & boats are repurposed examples.

     This concept has been replicated by landscape architect Dr. Deb Tolman in partnership w/ ranchers Jim & Mary Lou Starnater.  Their property, located on the edge of the Hill Country in the  community of Clifton, Texas is similar to southern Africa, “scorching heat, thin layers of topsoil, & elusive rainfall that can make for a brutal summer.”

The Beginnings Of Our Keyhole Garden

     We constructed our version in the Composting area using reclaimed materials & a bit of ingenuity.  Kevin used heavy cord & a large screwdriver to scribe a 6 ft. diameter circle on the ground as our reference point.  He and  Roger set 4 ft. metal stakes to hold fence wire into the basic circular shape w/ an inset wedge to provide access (keyhole) to the garden.  Into the center went the temporary vent/self-watering stack (later we’ll construct an inner basket measuring 1 ft. diameter & 4 ft. in height).  

Harvesting Compost For The Keyhole Garden

  The students from Independence Life Preparatory School  lined the interior and base of the keyhole garden structure w/ cardboard & set up alternating layers, 3 in. deep, bottom to top, of brown & green compostable matter.  The inner stack will also be filled w/ alternating layers (kitchen scraps & other herbaceous matter) of green & brown.

Annette With Students from Independent Life Prepatory School

 Unlock your own Keyhole Garden

Follow these guidelines to get started: 

1. Measure a 6-ft. diameter circle to define the inside wall of your garden.

2. Notch the circle (like cutting a wedge of pie) so you can access the basket at the center.

3. Construct the exterior walls about 3 ft. high using rocks, metal, timbers or any material that can support the weight of wet soil.

4. Use wire mesh to create a tube about 1 ft. in diameter & about 4 ft. high. Stand the tube in the center of the circle.

5. Line the outer walls with cardboard & fill the garden area (but not the wire mesh tube in the center), with layers of compostable materials, wetting down as you go. Fill the last few inches with compost. The soil should slope from a high point at the top of the center basket downward to the edges of the garden.

6. Fill the center basket with alternating layers of compostable material, along with layers of kitchen scraps & herbaceous weeds that provide the plants with moisture & nutrients.

7. Water the center basket & the garden only when the plants will not survive without it. This forces the plants’ roots down toward the center basket.

8. Feed the garden by adding more kitchen scraps, lawn clippings, etc. to the center basket.

9. Consider arching framework of thin wires over the garden. During the hottest months, the wires can support a shade cloth, & in winter, plastic sheeting creates an instant greenhouse.

10. Enjoy the fruits & vegetables of your labor!

Sources: Texas Co-op Power, Feb. 2012, pp14-15 “Keyhole Gardening: Unlocking the secrets of drought-hardy gardens” by G. Elaine Acker; http://www.urbanoasisproject.org/; www.sendacow.org.uk (Send a Cow Charity, Africa).

Watch this inspirational video,  Keyhole Gardening in Africa.

Annette

Get To Know Us

We are the Dallas County Master Gardeners at the Earth Kind® WaterWise Demonstration Garden on Joe Field Road. We hope you will get to know us and plan a visit to our gardens. 

We love compost and work hard at it.  Cindy, Sue, and Roger are adding green material to our compost bins. Believe me, our compost smells good. Roger is wearing the mask to reduce exposure to allergens.  Come take a whiff-we promise!

Master Gardeners Working with Compost

Adding green material to the compost bins at the Demonstration Garden

Planting those onions mentioned in the “Farm to Table” menu.

Planting Onions-January 2012

Onion Planting in January 2012

Jim adding drip irrigation to one of our raised beds.  If he can’t do it, nobody can!

Adding drip irrigation to a raised vegetable bed

“Cares melt when you kneel in your garden!”

Dallas County Master Gardeners at work, weeding in the Demonstration Garden

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