Oxisols

Oxisols Highly weathered and leached, residual Fe and A1 oxides Tropical areas with a stable landscape... 

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). 

H. Xing-Guo and C. F. Jordan, Mobilization of phosphorus by naturally occurring organic acids in oxisols and ulti.sols. Pedosphere 5 289 (1995). 

Fig. 1. Arsenate sorption (mmol kg 1) on Alfisol (A) and on Oxisol (B) in the presence of sodium nitrate or sodium nitrate + phosphate (PO4). Redrawn from Smith et al. (2002).

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... 

Laabs V, Amelung W, Pinto A, Altstaedt A, Zech W (2000) Leaching and degradation of com and soybean pesticides in an oxisol of the Brazilian Cerrados. Chemosphere 41 1441-1449... 

Brazil Southern Brazil No-tillage/ Oxisol 40,180 5.4 Sisti et al. (2004)... 

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. 

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. 

Two different pathways of formation are possible (Stanjek, 2000). One route involves aerial oxidation of lithogenic magnetite as suggested for Brazilian Oxisols on basic igneous rocks. The mechanism of this topotactic reaction is described in Chapter 14. These maghemites are usually titaniferous as are the magnetites from which they are derived (see Chap. 15) and almost free from or very low in Al (Allan et al., 1989). Their unit cell size is a function of the residual Fe" and the Ti content. 

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. 16.13 Charge properties as a function of pH of an oxidic-kaolinitic Oxisol B horizon (Brazil) with ca. 300 g kg Fe oxides as determined (left) by Na and Cl adsorption from a) 0.2 b) 0.1 and c) 0.01 M NaCI solution and (right) by potentiometric titration in a) 1 b) 0.1 c) 0.01 and d) 0.001 M NaCI solution (Van Raij 8c Peech, 1972 with permission).

Fig. 16.17 Sulphate adsorption and OH release curves of an Oxisol (Brazil Fed 77 g kg ) before and after removal of Fe oxides (Zhang et al., 1991 with permission).

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