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Pedogenic Influence on Base Saturation and Calcium/Magnesium Ratios in Soils of Southeastern Ohio

38 Spruce St., Selden, NY 11784

N. E. Smeck^* and J. M. Bigham

School of Natural Resources, Ohio State Univ., Columbus, OH 43210

*Corresponding author (smeck.1{at}postbox.acs.ohio-state.edu).

ABSTRACT

Contiguous Alfisols and Ultisols occur across the unglaciated, upland landscape of southeastern Ohio. Difficulties are encountered in distinguishing and mapping these soils due to morphological similarities and base saturation differences. The soils have formed in a loess mantle of varying thickness overlying colluvium and residuum derived from sedimentary bedrocks. Four pedons were studied to evaluate the influence of the loess mantle and bedrock chemistry on base saturation and extractable Ca/Mg ratios in order to facilitate soil mapping in southeastern Ohio. Loess thickness and Cr horizon chemistry could adequately account for base saturation and extractable Ca/Mg ratios in three of the four pedons, but a pedogenic effect is essential to explain extractable Ca/Mg ratios in the other pedon. In the latter pedon, extractable Ca exceeded Mg in both the loess mantle (upper solum) and deep Cr horizons, but extractable Mg exceeded Ca in the lower solum and uppermost Cr horizons. We conclude that bases leached from the loess mantle accumulate in the underlying residuum and that Mg is preferentially retained during base recharge. We speculate that a transient Mg-Al double hydroxide is formed in the residuum during base recharge and is responsible for preferential Mg retention.

Research support provided by state and federal funds appropriated to the Ohio Agricultural Research and Development Center, Ohio State Univ. Journal Article no. 26-93.

Received for publication January 3, 1996.