soil
Soil pH
Last reviewed 2026-10-04
Soil pH measures how acidic or alkaline a soil solution is on a logarithmic scale. A value below 7 is acidic, 7 is neutral, and a value above 7 is alkaline. Soil pH affects the chemical form and availability of nutrients, but it is only one part of soil fertility.
What it means
Because the scale is logarithmic, a one-unit change represents a tenfold change in hydrogen ion activity. Most garden plants tolerate a range rather than one perfect number. The useful target depends on the crop, soil texture, organic matter, irrigation water, and existing nutrients.
How it affects the garden
Test soil before applying lime, sulfur, or other amendments. A home test can provide a rough screening result, while a laboratory report can include pH, nutrients, organic matter, and recommendations. Changing pH takes time, and the required amount depends on the soil's buffering capacity, not pH alone.
The soil pH amendment calculator can estimate a material amount from stated inputs. Treat the result as planning guidance and follow the amendment label and soil test recommendation.
Example
A blueberry bed with a pH above the crop's preferred range may need a different plan from a vegetable bed with the same reading. The crop, soil type, and amendment history all affect the response.
Common confusion
pH is not a direct measure of fertilizer strength or organic matter. A dark soil can be acidic, neutral, or alkaline.
Sources
University of Minnesota Extension explains pH testing, nutrient availability, and amendment decisions.
