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Feeding the Soil

November 2014 Garden Lecture

“Thanking the Earth”

(Sub)urban Soils

  • (Sub)urban soils are usually of very poor quality.  They are hard, compact,  dry, and lifeless.
  • Before houses are built. the topsoil around the house is usually collected & sold. The remaining soil is compacted before the foundation is poured.
  • If you are on a hillside, you probably have a clay soil and if you live in a valley you probably have a sandy soil.


Shake Test

To determine the type of soil you have, use the shake test. Dig into the ground at least 6 inches. Fill a jar half-full with soil from this depth. Fill the rest of the jar with water and a few drops of soap.  Shake and allow the sediment to settle. You should see 3 distinct layers of soil: the largest is sand, and the middle size is silt, and the smallest is clay. Use the below chart to determine your soil type:


Nature as a Model for Building Soil

succession copy

  • Nature builds soil in stages. The progress through these stages is known as succession.
  • The stages move from supporting very little life, to supporting immense amounts of life
  • Generally, there are long periods of progress toward more life, and short periods of destruction.

Addressing the problems of (Sub)urban Soils

Lack of Nutrients & Biology

  • The first step of soil remediation is to create the  conditions for small life to happen. Soil that has no food for plants to eat, hard soil roots cannot break through, and no water to allow life cannot grow healthy plants or animals.

Feeding Soil in Small Areas – Sheet Mulching

  • For smaller areas, Sheet Mulching is an easy and effective way to provide an initial flush of nutrients to the soil.
  • Eventually microbes will colonize soil once food is available for them to eat, but we can speed up the process by inoculating the soil with a “starter culture” of healthy soil or high-quality compost.

Feeding Soil in Large Areas – Nitrogen-fixing plants

  • For large areas, initial food for the soil can be provided by plants themselves
  • NItrogen Fixing plants harvest free nitrogen from the air and put it into the soil where plants can access it.
  • All plants of the pea family fix nitrogen. Examples are fava bean, lima bean, peas, string bean, dry beans, lentils, soy, fenugreek and alfalfa.
  • These plants can all be used as a cover crop or green manure crop: they are grown only to increase the health of the soil
  • Cover crops should be cut down when they flower. At this point they have harvested the most sun, and haven’t started storing energy in seeds.
  • There are also a number of N-fixing trees and perennials such as black locust, Ice Cream Bean, Eleagnus Family Fruits (Lingaro, Autumn Olive, Goumi),

Breaking Up Hard Soils

  • Most hard soils are clay soils, but even sandy soils can become compacted and need loosening
  • Sheet Mulching will do a good job of loosening the first few inches of soil, but it will not loosen below that


  • To loosen soil at a deeper level, we can use soil-busting crops, these crops send down strong, deep tap roots that break up hard ground.
  • Examples of such crops are: daikon radish, burdock, sunchoke/jerusalem artichoke, and many tree species
  • How to use soil-busting crops:
    • Plant seeds over the area needing de-compaction
    • When the plant is at the flowering stage, cut all the plants just below the growing tip. If the plant re-grows, keep cutting it back until it dies
    • Allow the root to decompose in the soil
    • Alternatively, apply a sheet mulch over the cover crop when it is flowering

Maintaining Soil Moisture

  • All life needs water to survive.  Most food plants prefer consistent moisture in the soil.

Covering the Soil

  • Mulch is the easiest way to increase the water holding capacity of soil.   A mulch is a layer of material on top of the soil.
  • Examples of mulch material are: wood chips, straw, leaves, gravel, cardboard, newspaper
  • Soil should be covered with mulch  at all times.
  • In walkways, use 3-4 inches of wood chips as mulch
  • In beds, use a light layer of leaves and chopped up plants
  • Living mulches are plants with a creeping & spreading growth habit that can also be used as mulch.
  • When soil begins to dry out, irrigation can be used to re-moisten soil

Don’t Make a Swamp!

  • Make sure you do not over-irrigate
  • Too much water can clog up air pockets that microbes need to breathing, making the soil turn anaerobic.
  • Anaerobic conditions will kill almost all plants within 24 hours.

Harvesting Wild Manure

Everyone poops. Ants poop. Bees poop. Squirrels poop. Birds poop. We poop. Everyone poops. .All poop is food for the soil, and we can harvest that poop for free if we’re smart.

How to attract poopers

  • Put things in your garden  that poopers like to eat
  • Birds like to eat seeds, fruit, and nectar
  • Ladybugs like to eat aphids
  • Fungi like to eat wood
  • Bees eat nectar from flowers and collect pollen
  • Butterflies like to eat nectar
  • Dragonflies need water to reproduce