The role of iron oxyhydroxides in phosphorus chemistry of some East Texas forest soils
Forest soil phosphorus (P) chemical behavior was evaluated in some mid-rotation
fertilized loblolly pine (Pinus taeda L.) plantations in East Texas, that differed in their
site drainage characteristics. Forest floor mass and carbon content in the forest floor
were determined. Total P (PT) in the forest floor, and total and Mehlich-1 P and citratedithionite
(CD) and acid ammonium-oxalate (AAO) extractable P, Al, Fe, and Mn within
the mineral soil upper 100 cm were determined. Colorimetric determination of AAOand
CD-extractable P by the molybdenum blue ascorbic acid method, without the use of
pre-digestion, was assessed by an automated continuous flow injection system.
Phosphorus distribution between different operationally defined solid phases and its
relationships with CD and AAO extractable Mn, Al, Fe among depth, site, drainage class
and treatment were evaluated. Soil P forms were highly correlated with iron oxides
across sites, drainage classes, treatments, and depth intervals with significant differences
in P content and distribution in the soil profile and solid phases among drainage classes.
Soil P distribution patterns differed among drainage classes, yet it followed the
distribution of the iron oxides. Iron oxideÃ¢Â?Â?s role as a sink for soil P was higher in the
well-drained compared to the poorly drained sites. Amorphous phases of iron oxides
were higher in the poorly drained sites and dominated the role of iron oxides as a sink
for P under the poor drainage conditions. Fertilization resulted in significantly higher
forest floor mass, P content in the forest floor, and total P (PT) and CD-extractable P (Pd)
in the soilsÃ¢Â?Â? upper 10 cm. The treatment effect on P in the forest floor, and on PT and Pd
in the upper 10 cm of the mineral soil was equivalent to 6, 19, and 11% of the applied P, respectively. AAO-extractable P was highly correlated with Mehlich-1 P in the
fertilized plots. Treatment and site drainage class effects on P accumulation in the
different solid phases in the mineral soil and in the forest floor and the potential
contribution of these pools to P availability in subsequent rotations, following
clearcutting, are discussed.
Advisor:Messina, Michael G; Fisher, Richard F; Hons, Frank M; Loeppert, Richard H Jr.; Smith, Charles T Jr.
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:phosphorus iron oxide
Date of Publication:08/01/2005