September Task: Getting to Know Your Soil pH

An excerpt from the article “Soil pH as an IPM Tool for Disease Management” published in the September Crop Talk. The full article was written by Avishesh Neupane, Assistant Extension Professor, Department of Plant Science and Landscape Architecture and Shuresh Ghimire, Vegetable IPM Specialist, UConn Extension.

Off-target pH often shows up first as weak, yellow, uneven growth, and those areas commonly become the first disease hotspots. pH can limit root function and nutrient uptake, so plants run nutrient-stressed even when soil test levels look adequate. Crops also differ, so a pH that works fine for one crop can cause hidden nutrient stress in another. That stress doesn’t cause disease by itself, but it lowers plant tolerance and slows recovery once infection starts. Soil pH can also shift the soil microbiome in ways that reduce natural pathogen suppression. Soil acidification has been shown to weaken microbiome suppression of Fusarium, for example, allowing more disease under the same pathogen pressure and pH is a major driver of microbial community structure and function. The good news is pH is measurable and fixable, but it takes planning.

Tips to treat pH like prevention

1. Use crop-specific pH targets.
   There isn’t one ideal pH for every crop. Many vegetables, flowers, and turf do well in moderately acidic to near-neutral soils, while blueberries and other acid-loving plants need a lower pH. UConn’s Plant pH Preferences webpage lists recommended pH ranges by group. Start with the crop, then adjust pH based on field history.
2. Manage by zones when possible.
   pH can vary widely within a field due to soil type, past manure, knolls vs. low areas, and liming history. The most practical approach is to sample by management zones, map pH, and then apply lime (or sulfur, when needed) where the test shows it is required. If variable-rate application is not an option, you can still do zone management by targeting problem areas such as wet spots, sandy knolls, field edges, or specific blocks that consistently test low or high. In strip-till or bedded systems, banding lime in the worked zone helps correct pH where most roots grow.  In high tunnels and drip-irrigated blocks, manage pH at the bed or tunnel level. Adjust lime or sulfur rates by tunnel or bed based on testing, and if pH keeps drifting up over time, consider testing irrigation water alkalinity and managing it where feasible.
3. Plan changes early.
   Lime and sulfur take time to work. Limestone can take months to fully react, and it moves slowly downward in soil, so it is better to plan ahead than to try to fix pH midseason.
4. Do not compensate with extra fertilizer during disease pressure.
   If pH is off, nutrients may not be taken up well. Adding more fertilizer can increase salt stress and push soft growth that is harder to protect. Confirm the pH issue with a soil test, keep fertility steady, and time pH correction so the crop is in range before the next critical stage.
5. When symptoms show up, compare a good area and a problem area.
   If you see yellowing or patchy stunting, sample both: soil test and tissue test from a good zone and a bad zone. That helps you tell the difference between low nutrients in the soil and nutrients that are present but not being taken up.

Bottom line

Keeping pH in the right range helps crops take up nutrients, build stronger roots, and handle disease pressure better. It does not replace scouting or other IPM steps, but it makes them work more reliably and reduces problems in the weakest parts of the field.

You can learn more from the Integrated Pest Management (IPM) Team at UConn Extension through their quarterly Crop Talk e-newsletters.

Get Connected with CT Farm To School

• Get Listed: Join the CT Farm to School Directory and Marketplace-Listserv
  This interactive resource identifies farms throughout the state who are ready and eager to sell to schools. School Food Service Directors frequent this resource to find farms to purchase from.

• Learn More: Apply to join “Ready To Sell” farmer training cohort
  Participants in Ready to Sell learn about school buyer expectations, forward contracts, food safety considerations, and more. Get specialized technical assistance to up your school sales game. Learn more and apply here!

• Save the Date: October 5-9 is 2026 CT Grown for CT Kids Week
  October is National Farm to School Month, so naturally, the first full week in October is CT Grown for CT Kids Week when schools celebrate local agriculture, local food education, and strengthen their commitment to healthy nutritious meals with locally grown ingredients. Be part of it!