Laurel's Garden: Soil Temperature

Saturday, April 11, 2009

Soil Temperature

I bought a soil thermometer today so that I can figure out when to plant my early spring plants. The instructions advise inserting the thermometer "to a maximum depth of 2" to 3".

My soil temperature at 2" was 74F, at 6" it was 49F.
Current air temperature is 53F (near today's high).

At first, it didn't make sense that the soil would be that warm. But when I felt the top of the soil, it did in fact feel like it could be 74 degrees. The deeper soil felt pretty cold, but not close to freezing.

The instructions recommend the following soil temperature ranges:

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The Plot

The top 9 inches:

-imported topsoil
The next 3 inches:
-densely packed gravel
The next 2 plus feet:
-densely packed, sandy soil
-the foundation of a home

Soil tested 5/08 and 4/11
-Organic Matter 13.5% (high)
-Soluble Salts 0.8 (satisfactory)
-pH 7.5 (a bit alkaline)
-Phosphorus 50+ (very high)
-Potassium 300+ (very high)

2007

-Ground broken fall 2007.

2008

-I started gardening here in spring 2008.

-Added chicken manure, peat, and trace minerals.

-Hand-tilled soil to loosen hard packed gravel.

-Very few bugs, no worms or grubs.

2009

-Added horse manure in early spring and earthworms from a friend's garden.

-Hand-tilled soil in back half of garden.

-Water creates pools in areas.

-Some bees and butterflies. Occasional worms and grubs.

2010

-Fertilized with fish emulsion and blood meal.

-Slug problem, squash beetles emerge.

-Water still pools, runs off raised beds into path.

-Many butterflies, bees, and other insects.

2011

-Birds, insects, worms and grubs are abundant.

-Slugs and squash beetles are better this year.

-Soil re-tested. Nearly identical results as 5/08.

-Drainage better. Less hard-packed soil below.