HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Golden, D. C. Articles by Dixon, J. B. Search for Related Content PubMed Articles by Golden, D. C. Articles by Dixon, J. B. Agricola Articles by Golden, D. C. Articles by Dixon, J. B.

Seasonally Precipitated Iron Oxides in a Vertisol of Southeast Texas

MailCode SN4, NASA/JSC, Houston, TX 77058

F. T. Turner

Texas A&M Univ. Agricultural Research and Extension Center, Route 7, Box 999, Beaumont, TX 77713

H. Sittertz-Bhatkar

Electron Microscopy Center, Texas A&M Univ., College Station, TX 77843

J. B. Dixon^*

Soil and Crop Sciences Dep., Texas A&M Univ., College Station, TX 77843

*Corresponding author (j-dixon{at}tamu.edu).

ABSTRACT

The composition and crystallinity of Fe oxides in soils determines the reactivity and toxicity of Fe through redox and solubility reactions. The mineralogy and crystallinity of Fe oxides seasonally precipitating on ped surfaces and within soil pores and those forming around rice (Oryza sativa L.) roots were investigated by x-ray diffraction, electron microscopy, and electron microprobe analyses. Iron oxides precipitated on exposed surfaces of the League soil (fine, montmorillonitic, hyperthermic Oxyaquic Dystrudert), which is flooded during rice production, differed from Fe phases precipitated around rice roots. Iron oxides precipitated on ped surfaces and within soil pores were relatively poorly crystallized while those precipitated on rice-root surfaces were well crystallized. The presence of soluble Si and P during flooding may be responsible for precipitation of the less crystalline Fe oxides. Infrared and electron-diffraction data on the precipitate suggest the presence of PO₄ groups either adsorbed or coprecipitated with Fe oxide. Depletion of Si and P from the rhizosphere is believed to contribute to the formation of well-crystallized lepidocrocite on root surfaces. The poorly crystalline Fe-oxide precipitate that forms on ped surfaces upon draining and oxidation of the League soil has adsorbed or occluded Si and P. Thus, Fe oxides may influence the mobility of Si and P in alternately flooded and drained soils. Electron-diffraction data suggests that some of the Fe may be precipitated as strengite. Upon reduction and dissolution, these oxides release Fe, Si, and P into the soil solution and influence the nutrient dynamics in the rhizosphere of the rice plant.

Received for publication May 27, 1994.

This article has been cited by other articles:

				J. A. Ippolito, K. A. Barbarick, D. M. Heil, J. P. Chandler, and E. F. Redente Phosphorus Retention Mechanisms of a Water Treatment Residual J. Environ. Qual., September 1, 2003; 32(5): 1857 - 1864. [Abstract] [Full Text] [PDF]