Mineralization rate

The slow mineralization rate suggests the use of melamine for very long-term crops. Powdered melamine (Nitrazine 66N) is used in fertilizer spikes and stakes for houseplants and ornamentals. 

Many more papers deal with rhizosphere phosphatase activity (63-83) in the presence of a number of different plant species this will partly be due to the simplicity of the enzyme activity assay (85,86) and the generally reported, well-correlated variation trends among organic and inorganic phosphorus content and phosphatase activity. More precisely, closer to the roots, the inorganic P depletion zone in comparison with bulk soil is more pronounced in addition, organic and inorganic P contents are inversely correlated, and the mineralization rate of or-... 

Many bacteria possess a high-affinity urea uptake system accompanied by an intracellular urease enzyme (135). Nielsen et al. (136) have measured both natural urea turnover rates and gross N mineralization rates in situ using a new... 

Fig. 3. Plots of initial mineralization rates (IMR) versus equilibrium aqueous phase concentrations for naphthalene-degrading bacteria. Open circles represent Capac soil, closed circles represent Colwood soil, and squares represent soil-free control data points. Reprinted with permission from Guerin and Boyd (1992). Copyright (1992) American Society for Microbiology.

Even though only a small proportion of the non-harvested biomass returned to soil ends up in soil humus, SOC is needed to improve water infiltration rates and reduce erosion. SOC contents can be increased by adding more non-harvested biomass to soil or by slowing the mineralization rate of fresh biomass. 

For systems where the mineralization rate is dependent on the substrate concentration, first-order kinetics can be used to describe carbon turnover (Paul and Clark 1989 Six and Jastrow 2002). The first-order rate equation is... 

This equation can be converted to a linear equation, y = mX - b, by defining dSOC/dt as y, NHCa as x, and kNHC as m (Fig. 8.2). This derivation provides the theoretical basis for the maintenance requirements reported by Johnson et al. (2006). An important consideration of this derivation is that the y-intercept is the product of the NHC first-order mineralization rate constant (kNHC) and the NHC maintenance (NHCm) requirement, whereas the slope is the NHC rate constant... 

An alternative approach is to combine models with field measurements to assist in developing carbon budgets (Huggins et al. 1998). Clay et al. (2005) used first-order models to calculate the amount of residue returned to the soil from C3 and C4 plants over an 8-year period. Based on the mineralization rates and when the C3 and C4 residues were returned, the 813C signature of non-harvested biomass was determined. Based on the rates, carbon turnover, the amount of SOC mineralized, and the amount of fresh biomass incorporated into the SOC over an 8-year period were determined. 

Stumm, W., and E. Wieland (1990), "Dissolution of Oxide and Silicate Minerals Rates Depend on Surface Speciation", in W. Stumm, Ed., Aquatic Chemical Kinetics, John Wiley and Sons, New York, 367-400. 

Nair, D.R. and Schnoor, J.L. Effect of two electron acceptors on atrazine mineralization rates in soil. Environ. Sci. Technol, 26(ll) 2298-2300, 1992. 

The optimal pH area for the mineralization of RB137 is foimd to be between 6-9, i.e. at neutral and weak basic conditions, with the highest TOC removal, 88.7 %, achieved after 60 minutes at pH 8. It can be seen that the mineralization proeess is mueh faster in first 30 minutes of treatment process than in next 30 minutes. That ean be attributed to the formation of large quantities of organic acids, including those resistant to OH radical degradation, in the last 30 minutes of treatment with significantly lower mineralization rate. The decrease in pH value after the treatment in comparison to initial value corresponds to the formation of acid by-products, mostly aliphatic [92]. 

Abrams, S. A., Griffin, I. J., Hawthorne, K. M., Chen, Z., Gunn, S. K., Wilde, M., Darlington, G., Shypailo, R. J., and Ellis, K. J. (2005a). Vitamin D receptor Fokl polymorphisms affect calcium absorption, kinetics, and bone mineralization rates during puberty. JBMR 20, 945-953. 

Lake level could also influence silica levels. For example, the decline in lake level resulted in a large loss of surface area and decreased the amount of contact between lake water and sandy littoral areas that contain weath-erable silicate minerals. Rates of weathering are usually enhanced by acidification and would help to explain the interbasin differences observed at pH 4.7. However, weathering rates of LRL sediment are unknown (see Sediment Processes section). In addition, although the differences between the basins were significant, they were small (0.01-0.03 mg of Si02 per liter) and may be accounted for by small differences in hydrological factors. 

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