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Depth Matters: Soil pH and Dilution Effects in the Northern Great Plains
- Reeves, Justin L., Liebig, Mark A.
- Soil Science Society of America Journal 2016 v.80 no.5 pp. 1424-1427
- acidification, application rate, arid lands, soil acidification, soil analysis, soil pH, Great Plains region
- In the northern Great Plans (NGP), surface sampling depths of 0-15.2 cm or 0-20.3 cm are suggested for testing soil characteristics such as pH. However, acidification is often most pronounced near-surface (e.g., <10 cm). Thus, sampling deeper can potentially dilute (increase) pH measurements and therefore change management recommendations such as lime application rate. Here, we show evidence from two long-term (16-19 yrs) dryland cropping experiments that soil acidification at 0-7.6 cm was notably diluted at both 0-15.2 and 0-30.5 cm. Across studies and treatments, there were significant differences between depths for both final pH and pH change over time, with final pH being progressively higher and pH change smaller at deeper depths. Even in the young, highly buffered NGP soils, acidification can occur, and sampling depth for testing pH could be a consequential confound. We suggest sampling soils at 0-7.6 cm for testing pH in the NGP.