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Soil Health: Composting, and the Benefits of Intercropping and Cover Crops
Andy Waltke, M.S.
Creighton University
Common Soil Seed Library Lecture Series
What is soil?
• Biotic = living component• Bacteria• Fungi• Nematodes, worms
• Insects and larvae to larger animals
• Abiotic = not living• 3 components: clay, silt, sand (loam is equal mix)
• Finest to most coarse in particle size
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Soil Components
Soil Particle dimensions:Clay < Silt < Sand
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Organic Matter
• This is the most important component for home gardens and growing healthy plants
• This will retain moisture in the soil and is full of bioavailable nutrients for plants to use
• This is increased in soil by harboring natural biological life like earthworms and adding compost or mulches to garden spaces
• Needs water for biological processes, but also air so cannot become waterlogged• i.e. overwatering of plants kills them quickly
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Soil Chemistry• Complex web of interactions
• pH or potential hydrogen refers to how much free H+ or acid ions are in the soil
• May determine which nutrients are available for uptake
• Tropical plants like a lower pH soil like coffee or citrus, but locally we have alkaline or basic soils
• Soils are broken down into ions dissolved in water so plants may uptake them via roots
DIY Soil pH Test
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pH and Soil Chemistry
Rhizosphere
Roots breaking downsoil into soluble forms
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Biological Component
Some See This And Get Scared, but…
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World Wide Web of Fungi
• Almost all plants will grow in combination with fungi and those in turn will link plants or plant communities together!
• How plants communicate with one another
• Often the vehicle to deliver compounds between two different plants
Techniques For Proper Soil Health• No till or limited digging in garden
• Use of cover crops and intercropping methods
• Crop rotation and proper pest management
• Proper irrigation or watering
• Limit or do not use commercial chemicals
• Composting and vermiculture
• DO NOT want bare batches that will be prone to erosion and top soil loss
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No Till Gardening
• Limited to no digging in the garden
• Instead layers of natural mulches are used to suppress weeds and keep the natural soil strata in place
• Added over the season
Soil Layers or Horizons
• The biological component is at the top
• Digging or tilling disturbs the natural layering of soil
• Damages organisms and liberates weed seeds dormant in the soil
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Effects of Tilling the Soil
Cover Crops
• Retain top soil in place and are often low growing plants
• Many are in the bean family so will fix nitrogen from the air into a usable form
• These may be grown in the time between crops or overwintering
• Some grasses are grown to uptake excess nitrogen in soil if it was overfertilized
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Annual Cover Crops• Between crops during the warm season you may plant a cover crop to retain soil
‐ Buckwheat or Vetch
• In fall after harvest, plant cover crops that will emerge early in spring to activate soil before the growing season• Clover or Winter Rye
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Cover Crop Examples
Annual Rye GrassWhite Clover
Intercropping
• Maximizing use of space in garden
• Beneficial in retaining topsoil and mineralizing soil nutrients with increased roots growing
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Crop Rotation
• Will help to prevent buildup of soil pests and larvae so less chemicals are used in the garden
• Beyond pests, this ensures that the largest plants are not grown in the same space and exhaust any patch of soil
Hugelkulture Mounds
• Layering and mounding of materials to retain soil moisture and maximize the growing area of a space!
• Large logs are surrounded by smaller logs and all is buried with soil then gardened
• All decomposes over time while retaining moisture in the wood
• Creates microclimates
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Composting• Process mimicking natural decomposition
• Use garden waste, food waste, paper products, etc. to create compost rich in organic matter and biological life for your garden
• Process needs air, ideally contact with the ground itself, and moisture at about 50% but not waterlogged
• How to replenish soil nutrients year after year
• Greatly helped by worms in practice called vermicomposting or vermiculture
Composting Bins
Manufactured Tumblers
Wooden BinsCedar Wood orPallet Construction
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Greens to Browns• Greens are fresh kitchen scraps or garden waste that is fleshy and green
• Browns are twigs, dried leaves, cardboard, paper, etc or dry products
• Want to create a pile with alternating layers of each, so often add more browns than green to absorb excess moisture
• The pile will get hot and should kill weed or plant seeds if matured for enough time
Maintaining the Pile
• The pile will be turned with a pitchfork bringing the outer covering to the base of the pile. The more this is done the better
• If it smells then there is too much water, spread it out to dry some, add more browns.
• If there is lots of rain or in general I will cover the compost pile to keep in the internal moisture and heat
• Can lower the pH of the pile (more acidic) by adding pine needles or coffee grounds
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What not to add!
• Any meat or dairy products or cooked foods with oils. These may grow unhealthy bacteria in the pile!
• You can but I do not add eggshells, keep them aside, bake them in the oven to decontaminate before use in the garden (Salmonella danger)
• Styrofoam, plastics and non‐biodegradable goods
• Do not add diseased plant material or weed seed heads if possible – the pile will cultivate all life good and bad
Comfrey (cultivar Bocking 14)• Very useful plant in the garden and potent medicinal plant
• “Biodynamic” in that it will uptake lots of nutrients from the soil and often deep down
• Grow this plant then cut it down and add to the compost pile to increase its nutrient content
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Use of Compost
• Composting may be completed in a season or more than one depending on temperature, duration of winter, and moisture content
• To harvest, pile loose outer edges into a new pile and remove the black rich innards of the pile
• Spread this around you garden beds as a top dress, and especially around large or heavy feeding plants
• Do this every year from food and yard waste for a sustainable answer to your garden’s nutrient needs!
Vermiculture
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DIY Worm Bins for Your House
• Many designs to be found online
• If composting properly, they do not smell and the worms will eat half their weight in fresh scraps each day!
• Overwinters worms for outside bins
At the End of the Day…• Is it the soil?
• Or does it all come down to decomposition and the recycling of the natural resources in any yard or area.
• For example, the rainforest…• There is no nutrition in the soil, it is ancient clay• All life is in the biomass, therefore the engine of the rainforest is fungi and decomposition to make nutrients available again at ground level!
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We’re Just Farming Soil• Soil health in the long term comes down to many factors, but in general it is the active thriving organisms that drive the whole engine• From plant roots to microorganisms and bacteria
• However, through properly composting this also begins to address issue of household food waste – and I believe it opens the door to more people becoming aware of these issues
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The Danger of This Then Becomes Apparent
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Take stock at home…
• Examine the color and texture of soil
• Push on top with a stick to assess compaction
• Buy a simple pH meter to look at soil chemistry
• Limit chemical uses and find alternatives
• Make a compost pile or worm bin for indoors
• Make an effort to limit digging in the soil
• Limit patches of bare soil and plant cover crops
• Cultivate creatures in your yard and soil!
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Online Resources
• Nebraska Statewide Arboretum
• Wikipedia
• University of California Berkeley, author Robert Raabe, “The Rapid Composting Method”
• US Composting Council (http://compostingcouncil.org/resources/)
• EPA, Composting at Home (https://www.epa.gov/recycle/composting‐home)
