Categories Of Soil

The Four Scientific Categories Of Soil That Apply To You And Your Garden

SAND

Loose earth mainly composed of tiny particles of rock between 2 and .05 mm in size.  (Scratchy, gritty, won’t hold together.) Sand can get so dry it sheds water, but sandy soils drain well and seeds sprout in them much more easily than in other soils. Sandy soil eats up organic soil amendments.  Some sandy soils contain little nutrient of any kind, but they drain well.

• The main thing sandy soil needs is organic amendment.
• Manure is good on sandy soil since salts drain away quickly. Mulch annually or twice a year with clean horse manure. (Be sure to have an up-to-date tetanus shot.)
• If you do the above you will attain magnificent soil within a year or two.
• Apply organic mulch.
• Fertilize regularly with long-lasting organic fertilizers.
• Make and apply homemade compost.
• Return all kitchen scraps to the ground, except meat and bones unless in an enclosed system such as the Green Cone. (Excellent in sandy soil and full sun.)
• Avoid letting soil get so dry that it sheds water:
• If this happens, Use surfactants, products containing Yucca schigera a natural penetrant.
• Mulch lawns with bagged manure once or twice a year, spring and fall.

CLAY

Firm, fine-grained earth containing large amounts of tiny mineral particles, less than .002 mm in size with negatively charged surfaces.  Electric charge helps clay retain positively charged minerals – ammonium, magnesium, potassium, calcium, etc.  (Feels slippery and sticky when wet.  Damp handful holds together.)  Various colors: red (Terra Cotta), white, yellow, brown (Adobe).

Clay soils can bake hard on top and crack open in hot, dry, weather. Clay soil is heavy and difficult to dig, but it is minerally rich. Some clay soils don’t drain well, but on the other hand well-amended clay has the benefit of holding moisture, a big benefit in a dry climate.

• Do not amend clay soil with manure or you risk increasing salts.
• However, you can compost horse manure by layering it with spoiled alfalfa hay and make a wonderful compost you can then used for improving clay soil or any other soil.
• Mulch and add organics and you can make clay drain.
• Build raised beds filled with topsoil. (Nail wire on the bottom against gophers.)
• Add gypsum in the bottom of planting holes. If the cause of bad drainage is alkalinity, gypsum can improve drainage.
• Add between 2-5 pounds of gypsum for 100 square feet, as much as 10 pounds per 100 square feet on clay for seeding lawns.  Add more every 2 years (Organic gardeners prefer mined gypsum. Gypsite, which is water soluble, has been treated with chemicals to change its properties. It increases runoff.)
• Install sleeve drains on banks.
• Use commercial drainage pipes to drain low spots.
• How to check drainage before planting
• Fill the hole once, fill it again and if it drains one inch per hour drainage is adequate.
• If not adequate, fix drainage
• USE Drainage pipes
• Correct way to install with holes in sides or bottom.
• Use black plastic
• Avoid compaction by not standing on wet soil.
• Use an aerating machine on lawns annually and fill the holes with composted ground bark.
• Mulch lawns to increase humus content.

SILT

Fine-grained earth mainly composed of particles that are rounder and more weathered than sand.  Half-way in size between sand and clay particles. (Feels smooth, slippery, soapy, not sticky) Silt compacts easily when damp, but it is easy to work. It drains well but also retains moisture.

• Same solutions as for sand.
• Do not stand on wet soil after rain since silt compacts easily when wet.
• Use aerating machines on lawns annually and fill the holes with composted ground bark. Mulch lawns annually
• Apply humic acid to release nutrients.

LOAM

Combination of clay, silt and sand.  (Clay loams heavy, sandy loams light)  Fertile, holds water, drains well, but compacts. Loam is the ideal soil everyone wants. If you’ve got it, take good care of it. If you don’t have it, don’t try to manufacture it.

• Amend loam with organics to increase humus content.
• Mulch regularly to maintain humus content and keep loam loose and friable. ‘
• Avoid harsh chemicals that can lead to dead soil.
• Use organic fertilizers to maintain natural fertility.
• Don’t stand on soil that has been worked. Avoid soil compaction.
• Aerate and mulch lawns as explained above for clay and silt.

TWO ADDITIONAL TYPES OF SOILS OFTEN FOUND HERE THAT DON’T EXACTLY FIT INTO THE ABOVE FOUR (correct) CATEGORIES:

DECOMPOSED GRANITE

Grayish or light brown, granular, and sometimes flaky.  Mainly composed of variously sized particles of granite rock, some larger than sand.  (Feels loose, gritty and abrasive.  Sometimes packed down hard as rock.)

• Break up by rototilling and dig in organic matter.
• Plant cover crops of legumes.
• Minerally rich soil, increase water retention by adding organics.
• Mulch with manure.
• Add nitrogen for growth.
• Humic acid can help release natural nutrients in the soil.

CALICHE

A highly alkaline type of soil found largely in desert areas.  It’s high lime content may be visible as white flecks throughout or as a white crust on top of the soil, or it may occur in a hard buried layer.

• Try to break through to a layer that drains.
• Apply gypsum to wash away salts.
• Plant salt-resistant plants.
• Apply humic acid and leonardite if available.
• Apply compost and other acid amendments.
• Plant in raised beds.

FOUR PROBLEMS WITH SOIL FREQUENTLY FOUND HERE

ROCK-FILLED SOIL

So many rocks you can’t work the ground. Or such large rocks that you are gardening on top of rock.

• Use rocks for building walls, raised beds, and terraces.
• Never remove all rocks.
• Plant in raised beds.
• Make plant pockets like Hatshepsutt did.
• Build terraces on rock slopes and fill them with mushroom compost.
• Build dry stream beds, rock gardens, and design with rocks.

ROOT-BOUND SOIL

Often found in old gardens where large established trees, shrubs, climbers, and groundcovers fill the ground with invasive roots. (Eucalyptus, Melaleuca linarifolia, Monterey cypress, Algerian ivy, others.)

• Use the pot trick.
• Use root barriers.
• Plant in raised beds with root barriers beneath them.
• Plant in terraces.
• Use permeable paving for patios under trees.

HARDPAN

A layer of hard clay or other soil type that is buried beneath soil that drains. Often occurs when builders cover heavily compacted bulldozed ground with a layer of topsoil.

• If possible break through to a layer that drains.
• Understand the difference between sumps and drains
• SUMPS GO NOWHERE, (a swimming pool for roots!)
• Never use sumps. Sumps are entirely discredited.
• Use DRAINS. Drains lead water out or down through hardpan to a layer that drains.
• Plant in raised beds.
• Add gypsum to bottom of planting holes.
• Try double digging, (if you are up to it!)

BARE BULLDOZED GROUND

A layer of previously buried ground from which all the top soil has been removed.

• According to Greg Rubin, this is the best situation for planting native plants. So talk to him, attend his talks, and you can plant a garden of native plants, without the harmful soil fungi in garden soils that often kill native plants.
• Amend the soil by planting cover crops.
• Amend the soil by adding organics.
• Remove a foot or two of soil and replace with top soil, but be sure not to create hardpan by so doing. Create a marriage of soils: Loosen up the lower layer and mix in some top soil with it before adding the layer on top.