Microfarm Sustainable Research and Education

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That stuff you

walk on, . . .

dig in, . . .

scrub off.

That stuff you build your house on, . . .

bury your garbage in, . . .

sweep off your driveway.

That stuff you grow your food in.

How good is it?

How good do you want it to be....

when it's growing your food?


What is soil?

Soil is minerals (from ground up, weathered rocks) and organic matter (from decayed plants and animals and insects) and space (which is filled with water or air or sometimes both).

Soil is sand and silt and clay, usually found in various combinations. The particular combination determines your soil type. Silty clay loam, sandy clay, silt loam are all soil types. Your soil type determines how you farm.

Sand is made of large particles which can be easily seen. Sandy soil drains quickly, losing nutrients quickly.

Silt contains relatively fine particles that feel smooth and floury.

Clay contains the finest soil particles. They can be seen only with the aid of an electron microscope and becomes slick and sticky when wet. Clay soils drain slowly, causing stagnation and run off.


Soil Tests

You can do a test of your soil type at home.

  • Take about a cup of soil.
  • Put it in a quart-sized jar.
  • Fill the jar with water and cap it tightly.
  • Shake well to moisten all soil particles.
  • Then, set it aside for a day or two where it won't be disturbed. When you check it, the soil particles will have settled out in layers; sand on the bottom, then silt, then clay, then the organic matter on top.

The top layer, the decomposed organic material, determines the nutritional quality of your soil. It also helps develop the air-water relationship of your soil. A sandy soil is helped by the water-holding qualities of organic matter. A clay soil is helped by the clumping qualities of organic matter, separating the small clay particles into larger clumps, leaving spaces for drainage.


Nutrient and pH tests

To test your soil for nutrient levels and pH, you will need a soil test. This can be done at home with a kit. Check your local farm store or garden/nursery store. Or, for more complete results, send a soil sample to a lab. Some universities do soil testing through their extension service; if not, soil samples can be mailed to a lab. Check with your local Extension Service or look in the Yellow Pages under Soil Labs.


Improving Your Soil

Improving your soil does not mean fertilizing. Fertilizer is for the plants.

It does mean improved drainage, added depth, and added nutrients.

The best way to do that is by adding organic matter. Adding decomposed organic matter (compost), spreading manure, and turning under green cover crops are all effective methods of increasing the organic matter content of your soil.

Sufficient organic matter in the soil allows for both better drainage and better water-retention. Clay soils drain better with a higher organic matter content. And other soils, when rich in organic matter, absorb more rain water before eroding and retain that water for a longer time.

Regular additions of organic matter will also deepen the layer of topsoil. That's where most of a plant's roots are. Organic matter provides food for the soil's microbrial life who then provide nearly all of the nutrients plants require for proper growth.



Soil improvement also involves tillage. The method of tillage used affects the soil structure and how well what organic matter is there is utilized.

Traditional plowing is no longer considered the correct method of working in organic matter. If a green manure crop is plowed in, the organic material is loosened, turned over, and buried under the soil that was below it. Deprived of oxygen by this layer of soil, the organic material cannot decompose and therefore gives no benefit to the soil. Traditional plowing also creates hardpan, a pervasive soil problem that blocks root growth, blocks drainage, and blocks capillary action of sub-surface water. The tradition method of disking a field until the soil is finely pulverized can also be detrimental. Soil structure is compromised, and the small, finely pulverized particles of clay and silt are be easily blown or washed away.

New (?) methods of disking in crops are becoming more frequently used. Planting into the previous crops is also becoming more frequent.


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green marble line

Some photographs courtesy of Oregon Dept of Agriculture.

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