Part 1 – Introduction to Agricultural Lime and Liming. This section contributes to the discussion on the increasing incidence and severity of acid soils in the Inland Pacific Northwest (IPNW) and emphasizes: i) soil sampling and monitoring concepts to consider when managing acid soil conditions; ii) the role of soil testing; and iii) characterization of liming materials used to elevate pH of acidified soil.
Part 2 – Laboratory Testing to Determine Lime Requirements. This section delves more deeply into variations among soil types and why laboratory testing is used to characterize soil pH. We define the term “lime requirement” and how it relates to soil buffering capacity. We also provide information on lime requirement test methods commonly performed by soil testing laboratories. A companion Lime Requirement Worksheet based on common buffer tests and base saturation is provided for reference.
Part 3 – Aglime Product Selection and Comparison Calculator User Guide. This is a user’s guide for the interactive online Agricultural Liming Material Selection and Comparison Calculator. The publication describes the attributes used to perform calculations to characterize liming material, while the interactive utility provides a platform to compare up to three liming materials for their relative effectiveness, costs, and economic efficiency.
During the past fifty years, crop production in eastern Washington has undergone significant intensification. Fertilizer use, specifically ammoniacal-nitrogen, has increased more than sixfold to meet the nutritional needs of improved, high-yielding crop varieties (McFarland et al. 2015). This change in practice is contributing to the acceleration of a natural chemical process often referred to as soil acidification (Koenig et al. 2011).
The increasing incidence and severity of soil acidification in eastern Washington is evidence that landowners and producers may need to remediate acidified soils with liming materials to maintain soil quality (Anderson et al. 2013; Collins 2012; Mahler and Tindall 1998; Rasmussen and Rohde 1989). While the practice of liming soil with agricultural lime is the most common and effective solution for managing soil acidity, representative soil sampling, accurate soil testing, and liming material characterization are the keys to successful soil pH management.
Effect of Fertilizers
Mahler et al. (1982) reported that soil acidification in eastern Washington is increasing in severity because of increased use of ammoniacal nitrogen-based fertilizers. Table 1 lists common fertilizers and the calculated amount of calcium carbonate needed to neutralize the acidifying effects of nitrogen (N) or sulfur (S) in an unbuffered soil (Havlin et al. 2013). To counter the acidifying effects of fertilizers, a laboratory-determined equivalent application of neutralizing soil amendments (liming materials) should be included every three to six years as part of a nutrient management plan (Anderson et al. 2013; Brown et al. 2008; McFarland et al. 2015).
Soil Sampling to Identify and Monitor Soil Acidification
Georeference representative sampling points to monitor for changes in nutrients and pH from year to year or over time within the same season (Anderson et al. 2010).