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Tillage Pan Characterization of Selected Coastal Plain Soils¹

ABSTRACT

Tillage pan characteristics in Lakeland, Norfolk, Red Bay and Orangeburg soil series were studied at 20 paired locations of cultivated and virgin areas. Pits for sampling were dug following periods of heavy rainfall. Tillage pans were identified by pocket penetrometer readings of the compaction. Sampling depths from adjacent virgin sites corresponded to those in the cultivated sites. These pans showed consistently higher compaction, bulk density, and less pore space than the soil above or below the pan or the corresponding adjacent virgin soils. Sand, silt, and clay contents were not significantly different between virgin and cultivated samples.

Sequential extraction with hydrogen peroxide, dithionite-citrate, and 0.5N NaOH was made of the cultivated and virgin soils for depths above, in, and below the pan. Dithionite-citrate extraction for free Fe removed less Al and Si than the subsequent extraction with 0.5N NaOH. Accumulations of Fe, Al, and Si were significantly greater in the pan but these were not consistent for each soil series. Organic matter probably helped to filter and encourage accumulations of some compounds in the pan which might be important in cementation properties. Roots either failed to penetrate these tillage pans or were constricted to much poorer lateral growth compared to roots above or below the pan.

Key Words: porosity • aluminum • iron silica • root penetration

¹ Florida Agr. Exp. Sta. Journal Series no. 2459. Presented before Div. S-5, Soil Sci. Soc. of Amer., Stillwater, Okla., Aug. 22, 1966.

² Graduate Assistant, Soils Biochemist, Assistant Professor in Soil Dept., Gainesville, Fla., and Vice-Director at West Florida Exp. Sta., Jay, respectively

Received for publication August 25, 1966. Accepted for publication February 24, 1967.