Soil aggregation

J. L. Morel, L. Habib, S. Plantureux, and A. Guckert, Influence of maize root mucilage on soil aggregate stability. Plant Soil 736 1 II (1991). 

Emerson WW, Foster RC, Oades JM (1986) Organo-mineral complexes in relation to soil aggregation and structure. In Huang PM, Schnitzer M (eds) Interactions of soil minerals with natural organics and microbes. Soil Sci Soc Am, Madison, WI, USA, pp 521-548... 

Franzluebbers AJ, Wright SF, Steudeman JA (2000) Soil aggregation and glomalin under pastures in the Southern Piedmont USA. Soil Sci Soc Am J 64 1018-1026... 

Goss MJ, Kay BD (2005) Soil aggregation. In Zobel RW, Wright SF (eds) Roots and soil management interactions between roots and the soil. ASA, CSSA, and SSSA, Madison WI, USA, pp 163-180... 

Ikan R, Rubinsztain Y, Nissenbaum A, Kaplan IR (1996) Geochemical aspects of the Maillard reaction. In Ikan R (ed) The maillard reaction consequences for the chemical and life sciences. Wiley, Chichester, UK, pp 1-25 Jastrow JD, Miller RM (1998) Soil aggregate stabilization and carbon sequestration feedbacks through organomineral associations. In Lai R, Kimble JM,... 

Rillig MC (2004) Arbuscular mycorrhizae, glomalin, and soil aggregation. Can J Soil Sci 84 355-363... 

Chan KY, Heenan DP (1999) Microbial-induced soil aggregate stability under different crop rotations. Biol Fertil Soils 30 29-32 Chantigny MH (2003) Dissolved and water-extractable organic matter in soils a review on the influence of land use and management practices. Geoderma 113 357-380... 

Microbial biomass carbon Chloroform fumigation incubation Indicates soil microbial population various methodologies controls nutrient cycling and biological transformation necessary for soil aggregation dependent upon organic inputs Rice et al. (1996)... 

Green SV, Dao TH, Cavigelli MA, Flanagan DC (2006) Phosphorus fractions and dynamics among soil aggregate size classes of organic and conventional cropping systems. Soil Sci 171 874-885... 

The soil aggregates are assumed to be spherical in form and to have constant temperature and to contain initially uniform distributions of substrate (contaminant) and biomass. The external concentrations of biomass and substrate are assumed to be zero and the external oxygen concentration is constant. Substrate is adsorbed onto the solid phase to an extent determined by an equilibrium partition coefficient. 

Vary the radius of the soil aggregates in the range 0.1 to 10 cm and see how this influences the bioremediation time. 

Sexstone AJ, Revsbech NP, Parkin TB, Tiedje JM. 1985. Direct measurement of oxygen profiles and denitrification rates in soil aggregates. Soil Sci Soc Am 1 49 645-51. 

The effect of aggregation of the subsurface solid phase on kerosene volatilization was studied by Fine and Yaron (1993), who compared the rate of aggregation in two size fractions of a vertisol soil the <1 mm fraction and 2 mm aggregates. The total porosity of these two fractions was similar (53% and 55% of the total volume, respectively). Differences in aggregation are reflected in the air permeability that is, their respective values were 0.0812 0.009 cm and 0.145 0.011 cm Figure 8.10 presents the volatilization of kerosene as affected by the soil aggregation, when the initial amount applied was equivalent to the retention capacity. The more permeable fraction releases kerosene faster and thus enhances volatilization. 

Plate 16.1 e) Root channel in a gley soil stained by Fe oxide, f) Bleaching of the surface layer of a red soil aggregate by microbial reduction of the hematite. See root mat at the aggregate s surface supplying the biomass. 

Estimation of the relative effectiveness of nutrient sources can be a useful way in which to estimate their efficacy as fertilisers (Barrow 1985). The relative effectiveness of alternative nutrient sources is usually calculated by comparing the yield plateau of the response curve of the fertiliser in question to a soluble source of the same nutrients (Barrow 1985). For minerals used as nutrient inputs in organic farming systems their relative effectiveness is almost always <1 due to low solubility in soil. Organic matter inputs can also be evaluated in terms of their relative effectiveness based on their recalcitrance, but of equal importance is the extent to which they are physically protected from degradation in soil aggregates (Strong et al. 1999), which would be different in different soil types. 

Jordahl, J.K. and Karlen, D.L. 1993. Comparison of alternative farming systems. III. Soil aggregate stability. American Journal of Alternative Agriculture 8 27-33. 

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