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This article in SSSAJ

  1. Vol. 43 No. 4, p. 786-789
     
    Received: July 1, 1978


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doi:10.2136/sssaj1979.03615995004300040034x

Relationship of Ammonium Nitrogen Distribution to Mineralogy in a Hapludalf Soil1

  1. D. L. Sparks,
  2. R. L. Blevins,
  3. H. H. Bailey and
  4. R. I. Barnhisel2

Abstract

Abstract

Distribution of fixed and exchangeable ammonium were examined in three soil profiles of the Shrouts series from the Knobs region of eastern Kentucky. Shrouts soils (fine, mixed, mesic, Typic Hapludalfs) have high base status; exhibit strong, prismatic structure; and are derived from calcareous, high magnesium, soft (weakly cemented) clay shale. Soil pH ranges from 6.3 in the Ap horizon to 7.9 in the C. Analyses, using the Silva and Bremner procedure, showed considerable fixed NH4+-N in all horizons of each profile. Mean fixed NH4+-N in the profiles was 365 ppm for the Ap, 463 ppm for the B21t, 433 ppm for the B22t, 469 ppm for the C, and 543 ppm for the Cr horizons. Exchangeable NH4+-N also increased with depth, with values being about 1.2 to 1.5% of the fixed NH4+-N values. X-ray diffraction analyses of the clays and silts revealed predominantly mica in the 2–0.2 and <0.2 µm fractions, with some vermiculite present, and large quantities of mica in the silt fractions. High correlation (r = 0.92) was found between fixed NH4+-N and exchangeable NH4+-N. A correlation exists between fixed NH4+-N and mica + vermiculite content with an r value of 0.68. The fixed NH4+-N in the lower horizons is presumed to be indigeous, since no NH4+-N has been added recently to the soil.

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