Hello, thank you for your question!

It's a great question and you’re right that potatoes prefer slightly acidic soil to help reduce issues like scab. One important thing to note is that electronic soil pH probes from garden centers are often not very reliable, especially in raised beds where moisture and soil composition can vary. For the most accurate result, I’d strongly recommend submitting a sample to the University of Minnesota Soil Testing Laboratory (https://soiltest.cfans.umn.edu/). That will give you a dependable pH reading along with specific amendment recommendations for potatoes.

For potatoes (https://extension.umn.edu/vegetables/growing-potatoes), the ideal soil pH is around 6.0 to 6.5, though they will tolerate soil as low as 5.0. If your soil truly is near neutral (around 7.0), lowering pH is a longer-term process. Elemental sulfur is typically the best choice, but it works slowly and is most effective when applied in advance (fall or very early spring), as soil microbes need time to convert it and actually lower the pH.

Aluminum sulfate does act more quickly, but it’s generally not recommended for vegetable gardens because it can introduce excess aluminum and salts into the soil, which may negatively affect plant health over time.

For this growing season, you likely won’t be able to dramatically shift pH before planting. Instead, I’d suggest focusing on good overall soil conditions:

- Use well-drained soil, as poorly drained soils are more prone to tuber diseases

- Incorporate compost or well-aged manure to improve structure and add micronutrients

- Avoid over-liming or using any “weed and feed” products, which can harm potatoes

Once plants are established, fertilization is especially important for potatoes since they are heavier feeders than many vegetables.

For longer-term improvement, applying elemental sulfur this season (even if it doesn’t fully adjust pH right away) will help move your soil in the right direction for future crops.

Hope that information helps!

Best,

Victoria

University of Minnesota Extension Master Gardener