Lime Incorporation Depth and Application Rates

When discussing soil acidity, the conversation starts with the soil pH. pH is the measurement of hydrogen (H⁺) in the soil. It will determine whether the acidity in the soil needs to be adjusted. Next is the buffer pH. This is not recognized by all recommendation sources, but it is a very useful tool when preventing incorrect application rates. Next is the source of lime, depending on the soil analysis, to use calcitic or dolomitic limestone. The calcium carbonate equivalent (CCE) will determine when the product will reach its full potential by neutralizing the given soil acidity and plays a large role in application timing. The last piece of the liming puzzle, although there are many logistical steps not mentioned, is incorporation.

Many recommendation sources include incorporation rates for different tillage, or no-till, scenarios. Why does this matter? When correcting soil pH, it is not just the pH and buffer pH that determines the application rate but there is a volume of soil that makes a large portion of the equation. To interpret a soil analysis, the soil pH will determine is the soil needs lime. The lower the pH number, the more hydrogen or more acidic the soil is. A 5.5 pH is ten times more acidic than a 6.5. The buffer pH will determine how much to apply. The buffer pH is measuring the reserve acidity. A strong buffered soil will have a lower buffer pH analysis. A weakly buffered soil will have a higher number.

A physical lime prill, granule or particle will only neutralize a small amount of its surroundings. If the product is applied to the surface of soil, such as when practicing no-till, it will take an extended period of time for the product to reach the root zone of the intended crop. According to The Ohio State University, lime will only move into the soil profile at a rate of approximately 1” per year. This will be highly dependent on soil type and CEC. Before converting to a no-till system, it is important to start with a manageable soil pH. Or, if the soil is erodible, utilize options such as subsurface applications.

When surface applying lime, most sources will recommend a half, or reduced, rate. This is to prevent the surface soil from becoming overly alkaline. When a seed is planted it starts at the surface level, then it taps into deeper resources as it matures. This can create nutrient availability issues early in the plant’s life, but can outgrow them as a deeper, more robust root system develops. Even though a 6-8” soil core may result in a 6.5 pH, the top few inches could be 8 and the bottom part of the core a 5 pH in a no-till scenario. Tillage, although not applicable everywhere, creates uniformity to the tillage depth. This depends on tillage type, implement characteristics, disturbance level and soil type.

Always follow calibrated recommendation resources based on lab analysis. Lime applications are not an immediate fix and can take even longer depending on application practices, soil type and lime sources.

Johnson, J. W., & Myers, D. (2015). Most asked agronomic questions: Bulletin 760, Chapter 1—Liming and pH. The Ohio State University Extension.