Soil systems mineral cycling

Goh KM, Haynes RJ (1986) Nitrogen and agronomic practice. In Haynes RJ (ed) Mineral nitrogen in the plant-soil system. Academic Press, Orlando, pp 379—468 Golchin A, Oades JM, Skjemstad JO, Clark P (1994) Soil structure and carbon cycling. Aust J Soil Res 32 1043-1068... 

Figure 2 Conceptual model of carbon cycling in the litter-soil system. In each horizon or depth increment, SOM is represented by three pools labile SOM, slow SOM, and passive SOM. Inputs include aboveground litterfall and belowground root turnover and exudates, which will be distributed among the pools based on the biochemical nature of the material. Outputs from each pool include mineralization to CO2 (dashed lines), humification (labile slow passive), and downward transport due to leaching and physical mixing. Communition by soil fauna will accelerate the decomposition process and reveal previously inaeeessible materials. Soil mixing and other disturbances can also make physically protected passive SOM available to microbial attack (passive slow).

Physical and chemical erosion of continental rocks, represented by the arrow labeled "1" on Fig. 14-4, introduces particulate and dissolved P to the soil system. The majority (90%) of the P eroded from rocks remains trapped in the mineral lattices of the particulate matter. This P will be transported with the suspended material or bedload downstream until it eventually reaches the estuaries and the oceans, never having entered the biological cycles. The small proportion of the P that is leached from the minerals into solution, however, is readily available to enter biological cycles (2) and to react with inorganic soil particles (3). 

Corresponding to the analogy with potassium, a radiocesium cycle has been established in forest ecosystems which prevents radiocesium being lost from the mineral cycles of forest systems (Riesen, 2002). Either no or only very little radiocesium is lost by diffusion into the deeper zones of the soils (Sheppard and Thibault, 1991). [Under the presumption that the pH-value of the soils is low (<5.5) and there is a lack of potassium in the soils, these two conditions are fulfilled for almost all forests in Europe.] Almost all radiocesium cycles in the forest ecosystem function in the same... 

Guggenberger, G., and Haider, K. M. (2002). Effects of mineral colloids on biogeochemical cycling of C, N, P and S in soil. In Interactions between Soil Particles and Microorganisms. Impact on the Terrestrial Ecosystem, Huang, P. M., Bollag, J.-M., and Senesi, N., eds., IUPAC Series on Analytical and Physical Chemistry of Environmental Systems. Vol. 8, John Wiley Sons, Chichester, UK, pp. 267-322. 

Because of the low P content (usually < 0.2 %) of forage plants, P supplementation is commonly practiced in most ranches throughout the Amazon basin, particularly in Brazilian Amazonia. Assuming a stocking rate of 0.8 animal units per hectare per year, the annual input of P to the system through animal consumption of mineral supplementation would be around 2.0 kg, which is close to the amount expected to be exported annually by animal products (2.5 kg). The amount thus needed to balance the cycle would be only 0.5 kg. In the absence of phosphate fertilizer inputs, this P must come from the soil pool reserves, through forage consumption. 

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