Natural Ways to Lower Soil pH Level

Elemental Sulfur

• Typically OK with organic gardeners, elemental sulfur can lower a soil’s pH, according to the College of the Virgin Islands Cooperative Extension Service. The ideal application amount varies depending on the soil’s starting pH and type – with more sulfur needed for clay than sandy soil. Also, Organic Gardening recommends a greater amount for new gardens than for those that already have plants. Because of expense, growers should use sulfur on horticultural – not agronomic – plantings, according to The Ohio State University. Sulfur can take several months or more to affect pH because this type of acidification depends on interactions with microbes.

Peat

• Applying sphagnum peat is a good way to increase acidity in gardens, according to ISU. Mix a 1- to 2-inch layer of peat 8 inches to a foot down into the soil. Canadian sphagnum peat, which typically has a pH of 3 to 4.5, also adds organic material to the soil. However, as with sulfur, covering an expansive area may be costly.

Manure

• Routinely spreading manure onto soil raises acidity, although not to the extent of non-organic fertilizers, according to the University of Minnesota Extension. Manure includes material such as livestock feed waste and bedding – as well as feces and urine. While decomposing manure produces acids, its chemistry – including the presence of basic cations – can nullify acid creation or even raise the pH, according to the University of Nebraska-Lincoln Extension.

Compost and Mulch

• Adding compost to soil can either lower or raise pH, contingent on the acidity of both the compost and the existing soil, according to the U.S. Composting Council. Compost can also make soil more resistant to fluctuations in pH levels. The University of Minnesota recommends adding roughly 14 pounds of compost per square yard to lower pH by one unit. As for mulch, organic material such as pine needles can reduce pH, Organic Gardening reports. The slow-decaying needles, however, don't make the soil considerably more acidic.