Soils, oxisol

Aerobic soils of subtropical, mediterranean and humid to subhumid tropical regions (lateritic and plinthitic soils, red mediterranean soils, oxisols, ultisols). Usually absent in soils of temperate and cool regions. 

Naidu and Harter (1998) and Bolan et al. (1999), using soils having varied amounts of variable-charge components, showed that there was a significant increase in sorjition of Cd by soils (Oxisols, Xeralf) in the presence of sulfate... 

Figure 2.T. Elemental composition of an intensely weathered soil (oxisol) and a less strongly weathered soil, expressed as percent by weight of the oxide form. Also shown is the average elemental composition of the continental crust for comparison.

Other inorganic constituents. Many soils, especially in dry climates, are rich in forms of calcium carbonate such as limestone some soils may contain over 50% CaC03. This mineral is quite alkaline and contributes to elevated pH values which may exceed 8.0. Metal oxides in varying amorphous and crystalline forms may also be important constituents of some soils oxisols, for example, may contain as much as 80% Fc203 (Wolfe et al., 1990). Metal oxides may interact with clays and also with organic constituents of soils. 

On add, infertile soils (Oxisols, Ultisols, Dystropepts, Psamments, and Spodosols) the potential of trees to sustain soil productivity Hes in their role for maximizing soil cover (via canopies and mulch) and minimizing the loss of scarce nutrients via rainfall run off, soil erodon, and leaching 4). Due to reduced nutrient losses in systems with trees, the nutrient use efficiency of relatively small amounts of chemical fertilizers can be significantly improved. 

J. Gerke, W. Romer, and A. Jungk, The excretion of citric and malic acid by proteoid roots of Liipinus aihus L. effects on soil solution concentrations of phosphate, iron, and aluminium in the proteoid rhizosphere samples of an Oxisol and a Luvi.sol. Z. Pktnzenernaehr. Bodenk. I57 2S9 (1994). 

Dominy CS, Haynes RJ (2002) Influence of agricultural land management on organic matter, microbial activity and aggregate stability in the profiles of two Oxisols. Biol Fertil Soils 36 298-305... 

In data assembled by Greenland (1997), the mean level of organic carbon in the topsoils of wetland rice soils from across tropical Asia was 2%, and after excluding acid peaty soils the mean was 1 %. This compares with a range of 1.27-1.81 % for Oxisols and Ultisols of the Cerrado region of Brazil (Sanchez,... 

Sanchez PA. 1981. Soil management in the Oxisol savannahs and Ultisol jungles of tropical South America. In Greenland DJ, ed. Characterization of Soils. Oxford Oxford University Press, 214-252. 

Fig. 16.7 Electron micrographs of soil goethites. a) Acicular crystals from an Oxisol on peridotite. New Caledonia (Schwertmann, Latham, 1986 with permission), b) Starlike crystals from a redoximorphic paddy soil, China, c) Irregular crystals from an Ultisol on basalt, South Brazil (see also Schwertmann, Kampf,...

Fig. 16.19 Electron micrographs of natural associations between iron oxides and other soil minerals, a) Goethite (Co) crystals epitaxially grown on kaolinite (K) flakes (TEM) from a late-rite in Cameroon (courtesy J.P. Muller see also Boudeulle, Muller, 1988). b) Association of kaolinite (k), goethite (go) and hematite (he) in an Oxisol, Cameroon (SEM) (1987 courtesy J.P. Muller see Muller, Bocquier, 1986). c) Goethite accumulation between kaolinite...

J. Electrochem. Soc. 114 994-1000 Fontes, M.P.F. Weed, S.B. (1991) Iron oxides in selected Brazilian oxisols I. Mineralogy. Soil Sd. Soc. Am. J. 55 1143-1149 Fontes, M.P.F. Weed, S.B. (1996) Phosphate adsorption by days from Brazilian oxisols relationships with specific surface area and mineralogy. Geoderma 72 37-51 Fontes, M.P.F. Bowen, L.H. Weed, S.B. 

Iron oxides in selected Brazilian oxisols. II. Mossbauer studies. Soil Sci. Soc. Am. J. 55 1150-1155... 

Macedo, J. Bryant, R.B. (1989) Preferential microbial reduction of hematite over goethite in a Brazilian oxisol. Soil Sd. Soc. Am. J. 53 1114-1118... 

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