Friday, June 19, 2009

Garden Soil Test Results

Last week, I mailed soil samples from the Stoddart Garden and Bexley Garden to the University of Massachusetts at Amherst. (I had planned on testing the Stoddart Avenue Garden soil for lead after learning about problems in Buffalo, New York and on testing for nutrients after having concerns about yellowish zucchini. OSU no longer conducts soil tests and the UMass tests are inexpensive, include lead, and are easily researchable on the internet). UMass does not test for all possible toxins (like arsenic) or pesticides.

These are the results:


Because most of our vegetables prefer slightly acidic soil, I will bring some sulfer and peat moss to Stoddart Garden on Saturday and Wednesday if anyone wants to amend their soil and ever so slightly adjust their plot's pH (per the recommended methods discussed in Rodale's Successful Organic Gardening Vegetables book).

To get an idea of what the tested pH means, the following are the "ideal" pH for each type of vegetable (according to Rodale's):
Tomatoes: 6.0-7.0
Zucchini: 6.0-6.5
Potatoes: 5.8-6.5
Peppers: 6.0-7.0
Peas: 6.0-7.0
Onions: 6.0-7.5
Melons: 6.0-7.0
Lettuce: 6.0-6.8
Eggplant: 5.5-6.8
Cucumber: 6.0-7.0
Corn: 6.0-6.8
Carrots: 5.5-6.8
Cabbage: 6.0-6.8
Beans: 6.0-7.5

The UMass Report states:

Reported pH is higher than desired for a vegetable garden or flowers. Do not apply limestone, wood ash, potassium or phosphorus or any other amendment that might raise soil pH further. To lower pH: sulfur, alumnimum sulfate, or iron sulfate, or acidic organic matter may be effective. The required quantities of these materials will vary according to the nature of the alkalinity of your soil.

. . . In the fall before planting incorporate powdered sulfur into the top 8 inches of soil at 19 pounds per 100 square feet. For established plantings lightly topdress soil with podered sulfur at 1 to 2 pounds/100 square feet and maintain an acidic, organic mulch such as pine needles.

[The] soil contains very high levels of phosphorus and potassium. . . . Supply only nitrogen at 1/4 lb per 100 square feet. Possible sources are 1 lb of a 30-3-3 type fertilizer (free of any broadleaf herbicide) or 4 lbs of dried blood (an organic fertilizer).

Soil pH: 7.7 (alkaline)
Buffer pH 7.4

Nitrogen: NO3-N: 23 ppm
Organic Matter: 15.3% (Desirable range 4-10%)

Nutrient Levels: PPM
Phosphorus (P) 66 PPM -- Very High
Potassium (K) 946 PPM -- Very High
Calcium (Ca) 9185 PPM -- Very High
Magnesium (Mg) 901 PPM -- Very High

Micronutrient Levels: All normal

The lead level in this soil is low.

Cation Exchange Cap -- 67.8 Meg/100g
Percent Base Saturation K=4.4 Mg =13.3 Ca=82.5

Extractable Alumnimum 2ppm (Soil range: 10-250 ppm)

BEXLEY COMMUNITY GARDEN: Soil is slightly alkaline for most vegetables.

For what it's worth and as I previously explained at the Friends meeting, I only took one soil sample (as opposed to the recommended six samples which were then combined for an aggregate sample as I did in the Stoddart Garden). The UMass Report states:

The soil pH is slightly higher than desired for most vegetables. Cole crops may prefer the current pH since they are more resistant to clubroot infection under slightly alkaline conditions. Take care, however, not to incorporate any amendment that would further raise soil pH.

The soil contains sufficient levels for potassium. You may apply the standard recommendations , or you may provide sufficient nitrogen and phosphorus by using alternate sources to provide about 1/4 lb nitorgen and about 1/4 lb phosphorus per 100 square feet. . . . Avoid overfertilizing which can cause plant toxicity and can contribute to insect and disease problems.

Soil pH: 7.5
Buffer pH 7.4

Nitrogen: NO3-N = 5 ppm
Organic Matter: 8.3% (Desirable range 4-10%)

Nutrient Levles: PPM
Phosphorus (P) 16 ppm - Medium
Potassium (K) 293 ppm - Very High
Calcium (Ca) 7980 ppm - Very High
Magnesium (Mg) 469 ppm -- Very High

The lead level in this soil is low.
Miconutrient Levels -- all normal

Cation Exchange Cap -- 45.7 Meg/100g
Percent Base Saturation K=1.7 Mg =8.7 Ca=89.7

Extractable Alumnimum 4ppm (Soil range: 10-250 ppm)

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