Can I apply pelletized lime at planting and expect it to address my low soil pH rapidly in-season? While pelletized lime provides many benefits, such as quickly altering soil pH and possessing handling qualities that can make the application of the product more versatile, it has some limitations.
A traditional pelletized lime is a uniformly finely ground lime that has been pelletized using a binding agent. The chemical makeup of the lime material, final grind, and the binding agent can impact the rate of soil acidity neutralization. All these factors influence the rate in which the carbonate material becomes water soluble, and reactive with hydrogen ions, to neutralize the acidity. Likewise, the rate of reaction is impacted by soil incorporation and soil moisture.
The figure below (Jones and Mallarino, 2018) shows the relative rate of acidity neutralization as impacted by the fineness of a calcitic ag lime. If only the finest ground particles were applied to the soil, the rate of soil pH adjustment would take place quicker than a blend of particle sizes. In addition, the pelletizing of the finely ground lime greatly increases the uniformity of spreading and handling characteristics in fertilizer systems designed to handle granular fertilizer.
This data was generated from an experiment conducted in a laboratory to control the environmental factors/conditions so that the research is repeatable. Primarily maintaining a constant soil temperature and moisture at 80-90% of field capacity. If we were to move this study to a field, fluctuations in temperature and soil moisture would impact the data. Lower soil temperatures and drier soils would slow the rate of reaction, especially for the more finely ground fractions.
The figure below from the same study (Jones and Mallarino, 2018) shows the relative rate of acidity neutralization as impacted by the product used. The results of the pelletized lime closely follow the results from the 60-100 mesh grind. Faster than traditional ag limes, but still slower than pure calcium carbonate when applied at equal rates.
Both the pelletized lime and the calcitic lime has similar pH impacts for the first 21-35 day of this experiment as the finely ground portion of the calcitic lime reacted similar to the fine grind of the pelletized lime.
This figure also shows that while pelletized lime increases soil pH more than calcitic lime when applied at equal rates, it also takes pelletized lime in excess to 100 days to reach a maximum soil pH adjustment. That is a over 3 months, or slightly longer when taking field environmental factors into consideration. If the pelletized lime is applied at planting the first of May, maximum pH will be achieved the bringing of August at the earliest. By this point in the season altered nutrient uptake and growth may have already negatively impacted crop yield.
If pelletized lime is routinely applied every year, timing is not critical. If this is a recue application of pelletized lime to make a quick pH adjustment to a neglected field to avoid yield loss, fall to late winter application of the pelletized lime prior to the growing season will have a bigger impact on in-season soil pH levels when compared to an at-planting application. While pelletized lime is a very useful tool in fertility management, it still takes time for pelletized lime to make meaningful soil pH adjustments.
Source: Jones, John D., and Antonio P. Mallarino. “Influence of Source and Particle Size on Agricultural Limestone Efficiency at Increasing Soil PH.” Soil Science Society of America Journal, vol. 82, no. 1, 2018, pp. 271–282., doi:10.2136/sssaj2017.06.0207.