Evaluating buffer methods for determining lime requirement on acidified agricultural soils of the Palouse

Abstract

Acidification of agricultural soils under intense management in the Palouse region of eastern Washington and northern Idaho is of increasing concern. Buffer methods can provide lime requirement estimates (LREs); however, locally calibrated methods are lacking. Our objective was to evaluate buffer methods and to determine which can produce optimal LREs for Palouse agricultural soils. Samples from 10 regionally dominant agricultural soils (initial pH ≤5.3) were assessed for pH changes after incubation with nine levels of calcium carbonate (CaCO 3) for 90 d under laboratory conditions. Achieving a target pH of 6 in the top 15 cm of the soil profile required 3.36-8.36 Mg ha −1 of CaCO 3. Laboratory incubation results were compared with LREs calculated from 10 established calibrations using data from seven buffer methods:

Evaluation of nonhazardous lime requirement estimation methods for Oregon soils

“…These soils had lower clay and SOM concentration, 104–403 g kg −1 and 32–67 g kg −1 , respectively. Prior lime incubation studies saw similar lime incubation response, with a linear response below pH 6.5, and with decreases in slope above pH 6.5 (McFarland et al., 2020; Peterson, 1971). Apart from the six highly buffered soils (Awbrig, Bashaw, Bellpine, Jory, Nekia‐1, and Nekia‐2), soils collected from the Willamette Valley appeared to respond to CaCO 3 addition similarly to soils from central and eastern Oregon.…”

“…Regional laboratories from New Jersey, Texas, Maryland, Connecticut, and Delaware reported using soil texture class in conjunction with soil pH or SOM and soil pH to make lime rate recommendations (Follett & Follett, 1983). McFarland et al (2020) also did not show a strong relationship between clay content and F I G U R E 4 Linear regressions between incubation lime requirement and lime buffer capacity methods, for 24 Oregon soils. The Ca(OH) 2 regressions were evaluated using the Kendall-Thiel method.…”

“…Soil exchangeable Al is a source of acidity in soil; therefore, Al may be related to lime requirement (J. T. Sims, 1996). Although these individual properties are all related to soil acidity and lime requirement, previously developed LRE methods have used two or more soil properties to achieve an acceptable lime estimate (Keeney & Corey, 1963; Lemire et al., 2005; McFarland et al., 2020; Miller et al., 2005).…”

“…Lime requirement estimation (LRE) methods based on soil properties have been developed and evaluated (based on regression with lime incubation studies) in various regions of North America, including Wisconsin (Keeney & Corey, 1963), Quebec (Lemire et al., 2005), California (Miller et al., 2005), and eastern Washington State (McFarland et al., 2020). These methods may not be effective for Oregon due to differences in soil characteristics.…”

“…(2020) were shown to be acceptably accurate for estimating LR in their respective regions, based on r 2 values ranging from .71 to .88. However, each model had slightly lower r 2 values than at least one buffer method evaluated in the same study, indicating that, in general, buffer methods were more accurate for estimating lime requirement than methods based on multiple soil test properties (Keeney & Corey, 1963; Lemire et al., 2005; McFarland et al., 2020; Miller et al., 2005). Although soil properties have shown promise in other parts of the United States for LRE, this approach has not yet been evaluated for Oregon agricultural soils.…”