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What you need:
  • Soil pH test kit
  • Limestone to raise pH
  • Aluminum sulfate or sulfur to lower pH
pH (potential Hydrogen) is the measure of the general acidity or alkalinity of a soil. If the soil is too acidic or too alkaline, needed nutrients can be 'tied up' in the soil and not available to the plants. Nutrient deficiencies can result.
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A purchased pH test kit will give you an idea of your soil's pH. You can not 'look' at a soil sample and determine its pH. For more exact results, you should submit a soil sample to your local or state Cooperative Extension office or a soil testing lab. A pH of 7 is neutral. Anything lower than 7 is acid (sour) and anything higher (sweet) is alkaline. A slightly acidic soil of 6 to 6.5 is ideal for most plants. It is important to know the pH preferences of the plants you are growing!
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If your soil is too acidic (below 6), limestone can be added. To increase the pH by 1 unit you need to apply ground limestone at the rate of 35 lbs. per 1000 sq. ft. on sandy soils and up to 80 lbs. per 1000 square ft. for clay soils. Large applications should be split in half - apply 40 lbs.now, then make the second application 2-3 months later.
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If your soil's pH is too high, aluminum sulfate or sulfur can be added to lower it. See your soil test results for specific amounts to apply. Most organic mulches have an acidic reaction which can also be helpful in lowering soil pH.