Finding out soil composition

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Judy81350 Queen Creek, AZ(Zone 9a) Jun 23, 2005

This is cool. I just got my Arizona Gardening book and in it, there is a description on how to tell what kind of garden soil you have. Maybe this could help some of you. This is for the desert but I don't know why it couldn't work for any state. All one can do is try it.

You can easily find out how much sand, silt and clay your soil has if you put a cupful of soil in a tall quart jar. Add 4 cups of distilled water and a tsp. of Calgon to act as a dispersing agent. Shake vigorously for 5 mins. and then put the jar on a shelf in good light and let everything settle. After 5 min. the sand will be resting on the bottom and in 30 mins. the silt will be lying on top of it. The clay particles may still be in suspension, but after a day they will have settled out to form a third layer. The water will be clear, but brownish-colored, depending on the amount of humus present in the soil. Bits of organic matter will be floating on the top. A lot of organic matter and a pale solution indicates a recent application of manure or compost that hasn't decayed. On the other hand, a dark brown solution and very little material floating on top suggests the soil is from an old garden. Measure the 3 layers and calculate the percentage of each. A good garden soil has roughly 70% sand, 15% silt and 10% clay, with some humus and some organic matter ready to decay into more humus. Carry out this mechanical analysis on some raw desert soil and soil from a good garden. Let them settle in a jar and look at the differences.



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spectrum (Zone 2b) Jun 24, 2005

The sand/silt/clay percentage part of that will work on most soil types, with the possible exception of soils that are extremely high in organic matter (eg - soils from peat bogs). It is reasonably similar to the method for determining soil texture used in many soil science laboratories. Another way of determining soil texture is 'hand texturing', which basically involves rolling the wet soil into a ball, squeezing it into a ribbon, and feeling how smooth or gritty it is and then comparing it to a chart. Hand texturing takes some practice to get good at.

The water color will be more variable in different locations, and could be due to other reasons in other places.

This message was edited Jun 23, 2005 6:46 PM

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Judy81350 Queen Creek, AZ(Zone 9a) Jun 24, 2005

Tomorrow I think I'll try this test. I need to get some Calgon though. I think my soil is pretty good for desert soil because everything I've planted so far, including the avocado, are growing like crazy. Thats probably my best indicator. lol Thanks for the additional info.

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