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Changing Soil pH

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High pH (Alkaline)

Sulphur applications can be used to lower pH levels in soil if there is little to no free lime in the soil being treated. A simple test, like the one for testing overall pH can be preformed by taking a tablespoon of dry soil and moistening it with vinegar. If it fizzes not only is the soil very alkaline but you should avoid using a sulphur treatment you may damage your plants.

In the pressence of free lime other treatments such as:

  • Elemental Sulphur - Available to purchase in most garden center and hardware stores. Works slowly over time.
  • Some Feritlizers - Some nitrogen rich fertilizers will lower soil pH but in barely noticable amounts.
  • Coffee Grounds - Added and mixed to soil will help to lower pH levels in soils, can be used indoors and out. Effects a little quicker than sulfur but not suitable for large scale pH reduction, unless you drink as much coffee as I do. When the acidic effect of the grinds wears off the pH will rise again.
  • Vinegar - A tablespoon mixed with the water you use to water your plants can help a great deal in lower soil pH. Effects are very quick so be sure not to over do it, just use small amounts at a time. Short lived fix and the pH levels will rise when the acid in the vinegar has broken down.

You can also add ingredients for long term solutions to pH such as sawdust, composted leaves, wood chips, cottonseed meal, leaf mold and peat moss.

Low pH (Acidic)

Raising the pH levels of soil is generally more simple than lower pH levels. The addition of dolomite lime, hardwood ash, bone meal, crushed marble, or crushed oyster shells will help to raise the soil pH.

  • Dolomite lime -
  • Hardwood ash
  • Bonemeal
  • Crushed marble
  • Crush oyster shells

Changes to soil pH will take time to begin to show. Remember to add small amounts and observe the results to prevent damage to your plants!