Healthy soil is the foundation of productive and resilient farms, and soil chemistry plays a critical role. Soil chemical health refers to the balance of nutrients, pH, and other chemical interactions that determine how effectively soil can support crops while protecting water quality and the environment. These properties influence everything from how nutrients are stored and released to how well plants can take up nutrients to the long-term sustainability of farm productivity. For Ohio farmers and land managers, understanding the chemical health of soil is especially important because of Ohio’s naturally acidic soils, widespread use of tile drainage, and water quality challenges linked to harmful algal blooms in Lake Erie and other watersheds. The goal of this fact sheet is to introduce the basics of chemical health in soil as a pillar of overall soil health—to help producers connect the science of soil chemistry with practical management strategies that support profitable farming and environmental stewardship.
What Are Soil Chemical Properties?
Soil chemical properties refer to nutrient content, pH, and chemical interactions that influence the ability of soil to support plant growth and environmental functions. In Ohio, maintaining balanced soil chemistry is essential for productive farming, water quality, and long-term soil health. Soil fertility is largely governed by soil chemistry, as pH determines nutrient availability, and cation exchange capacity (CEC) determines how well nutrients adhere to soil in the root zone.
Key Soil Chemical Properties
Soil pH
- measure of soil acidity or alkalinity (Figure 1)
- affects nutrient availability, microbial activity, and metal toxicity
- ideal range for corn is 6.0–6.8, soybean is 6.2–6.8, and wheat is 6.0–7.0
- Ohio soils are largely (or can become) acidic and thus require lime (CaCO3) additions periodically to raise pH to optimal conditions for crops
Cation Exchange Capacity (CEC)
- the ability of a soil to hold and exchange nutrient cations (e.g., Ca2+, Mg2+, K+) (Figure 2)
- CEC is driven by clay content and organic matter
- clay content is impossible to change
- CEC can be improved by increasing organic matter content via cover cropping, manure/compost additions, and retaining in field crop residue
Base Saturation
- percentage of CEC occupied by essential cations (e.g., Ca, Mg, K)
- relatively high base saturation indicates better fertility
- soil with a pH of 6 or 7 typically has a base saturation of ~70% or ~95%, respectively
- optimal base saturation supports pH buffering (resistence to change) and nutrient uptake
Electrical Conductivity (EC)
- measure of soil salt content
- generally, EC is low in most Ohio soils, but it is important to monitor EC in irrigated or compacted areas (EC value more than 4 dS/m is problematic)
- high EC can lead to surface crusting, inhibiting seed germination and water uptake (this is infrequently an issue in Ohio soils)
Nutrients and heavy metal contamination
- measure of plant-available, macronutrient concentrations (e.g., nitrate-N, Mehlich-3 P and K) is essential for crop production
- measure of plant-available, micronutrient concentrations (e.g., Mehlich-3 Fe, Zn, Mn, Cu) is also essential for crop production
- although these nutrients are needed in small quantities, a lack of micronutrients can lead to deficiencies and yield reductions
- in urban settings, monitoring concentration of heavy metals such as lead (Pb) and arsenic (As) is crucial for maintaining soil chemical health, as is developing remediation strategies to help alleviate potential risk to humans, animals, and the environment
Common Chemical Soil Health Challenges in Ohio
Ohio faces a number of soil health challenges related to chemical properties, namely soil acidification, phosphorus (P) saturation, and nutrient leaching. In Ohio, where soils are naturally slightly acidic, the addition of ammonium-based fertilizers lowers the pH to levels that decrease nutrient availability and therefore, also reduce crop yield. Consistent soil testing for pH and nutrient concentrations, along with adding lime (e.g., CaCO3) to raise pH into the ideal range for crops, are both needed to mitigate this issue. Historically, heavy manure applications and overapplication of P fertilizer have led to soil P saturation. This saturation has increased the risk of P runoff and leaching into watersheds, eventually causing harmful algal blooms, particularly in Lake Erie’s Maumee Bay. Regular soil fertility testing—particularly zone-based testing to guide variable-rate, fertilizer applications—is recommended to help prevent P over-application, lower input costs, and improve efficiency. Overall, maintaining balanced soil chemistry is essential for maintaining productive farms, improving water quality, and ensuring long-term soil health.
Understanding the chemical health of soil as it relates to other soil factors may be beneficial to farmers. For example, knowing that increases in soil cation exchange capacity also increase aggregate stability (a physical soil-health parameter) and organic matter (a biological soil-health parameter) helps farmers nurture their soil toward its optimal health. These relationships and others are available in the Ohio State University Extension Soil Health Survey Across Ohio Farms (soilfertility.osu.edu/sites/soilf/files/imce/Soil%20Health%202020%20eFields%20Report_article.pdf).
Practices to Improve Soil Chemical Health
Best Management Practices (BMPs) to improve the chemical health of soil revolve around soil testing, proper interpretation, and precision agricultural techniques. Soil testing to inform variable lime and nutrient application rates (in the case of precision agriculture) and utilizing the 4R principles (right source, right rate, right time, and right place) for nutrient management are two beneficial strategies for improving the environment and farm profitability. Balancing manure additions with soil P levels, implementing cover crops, and using buffer strips are all BMPs that can improve the chemical health of soil and reduce environmental impacts. Solutions to mitigate water quality issues associated with excessive P saturation include two-stage ditches that filter tile drainage; the use of chemical coagulants at key, strategic locations across landscapes (e.g., Al- or Fe-based drinking water treatment residuals); and improving the physical health of soil to reduce soil runoff.
Conclusions
Maintaining optimal soil chemical properties is essential for prosperous agriculture in Ohio. Chemical characteristics such as pH, nutrient availability, and CEC directly influence plant growth, soil biology, and environmental quality. When these properties are optimized, soil can support healthy crops, minimize nutrient losses, and reduce negative environmental impacts. By utilizing regular soil testing and implementing BMPs, Ohio farmers and land stewards can protect and enhance the chemical health of their soils while maintaining or improving crop yields.
Additional Resources
- Baseline Assessment of Soil Health in Ohio
(soilhealth.osu.edu/sites/soilhealth/files/imce/WhitePapers/Baseline%20Ohio%20Soil%20Health.pdf) - Biological Soil Health
(ohioline.osu.edu/factsheet/anr-0205) - USDA-NRCS Soil Quality Indicators Fact Sheet
(nrcs.usda.gov/sites/default/files/2022-10/indicator_sheet_guide_sheet.pdf) - Physical Soil Health
(ohioline.osu.edu/factsheet/anr-0203) - Soil Health
(ohioline.osu.edu/factsheet/anr-0202) - Soil Health Survey Across Ohio Farms
(soilfertility.osu.edu/sites/soilf/files/imce/Soil%20Health%202020%20eFields%20Report_article.pdf) - Soil Health Testing
(ohioline.osu.edu/factsheet/anr-0206) - Soils and Soil Health
(ohioline.osu.edu/factsheet/anr-0136) - Two-stage Ditches
(ocj.com/2022/09/ditch-design-options)