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I had my soil tested. The ph is 8.2. What is the best product to lower the ph. I’m reading about sulfur, aluminum sulfate and peat moss. Peat moss looks like the best bet but how much do I need to add?

Niall C.
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Jean
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  • a hard question to answer without more details, type of soil--clay or sand or ?? location in the world, what does grow well there? – kevinskio Apr 17 '21 at 18:04
  • Another factor to consider with pH is where in your property the soil sample(s) was taken? Was it near a building foundation? A concrete wall or driveway? A retaining wall? These are all sources of alkalinity that can affect sampling for pH. – Jurp Apr 18 '21 at 12:33

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Edward J. Plaster, author of Soil Science and Management, 5th edition, recommends using sulfur to acidify the soil and not peat moss to lower pH. He states that peat moss is a temporary solution to the problem because as it decomposes its pH-lowering ability diminishes to zero and the soil's pH will then return to its original figure. OTOH, if you have clay soils then the peat moss will at least add some organic matter to the soil and improve its drainage. You'll still have high pH, but you'll have better soil for gardening.

If you want to follow Dr. Plaster's recommendation, in the work I've cited (p. 247) he shows a chart that recommends the amount of sulfur need to lower the pH by 1.0 over two different areas. Here are the figures in both Imperial (and, I hope, correct) metric amounts and areas.

Imperial

Pints per 100 square feet
Sand - 1.33 pints
Loam - 4 pints

Pounds per acre
Sand - 725
Loam - 2200

Metric

Liters per 9.3 square meters
Sand - 0.63 liters
Loam - 1.9 liters

Kilograms per acre
Sand - 329
Loam - 1000

1 acre = 0.405 hectare, so 1 hectare = 2.47 acres, yielding (I hope):

Kilograms per hectare
Sand - 812.63
Loam - 2470

No matter which measuring system you use, this is A LOT of sulfur. If planting a vegetable garden, you'd probably be better off using raised beds where you can more easily control pH and if planting a landscape, you'd be better off following the adage 'right plant, right place' and planting only plants that like higher pH soil.

Jurp
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