Organic residue decomposition

The rate of organic residue decomposition in soils and related environments is ultimately controlled by its biological stability, which is a function of the following four main factors, namely, (i) its biochemical recalcitrance, (ii) the biological capability and capacity of the environment, (iii) decomposition rate modifiers (e.g., temperature, moisture, exposure time) and (iv) physical protection mechanisms (Baldock et al., 2004). Recent studies have shown that the physical protection mechanisms, such as the spatial inaccessibility of organic matter in soil micropores, are the most important factors in controlling the stability of organic matter in soils (Mikutta et al., 2006 von Liitzow et al., 2006). 

The only accident that involves a saturated ester is the result of an attempt to extract an organic residue containing hydrogen peroxide with ethyl acetate. The latter was mixed with methanol and refluxed with the residue and hydrogen peroxide in an aqueous solution. A second extraction was carried out with acetate and the liquid was then evaporated. The small quantity of the compound that remained after the evaporation detonated violently. It was thought that this detonation was the result of the violent decomposition of methyl hydroperoxide, peracetic acid and/or ethyl peracetate. 

Neutral interactions are found extensively in the rhizosphere of all crop plants. Saprophytic microorganisms are responsible for many vital soil processes, such as decomposition of organic residues in soil and associated soil nutrient mineralization/turnover processes. While these organisms do not appear to benefit or harm the plant directly (hence the tenn neutral), their presence is obviously vital for soil nutrient dynamics and their ab.sence would clearly influence plant health and productivity. 

Few studies have been conducted to determine organic residues in spent foundry sand and leachates from disposal sites. It is reported that several organic compounds are present in the spent foundry sand but have concentrations below the regulated toxicity characteristic limits. Organic compounds of concern include benzoic acid, naphthalene, methylnaphthalenes, phenol, methylenebisphenol, diethylphenol, and 3-methylbutanoic acids.12 These compounds are thought to be derived from the decomposition of organic binders such as phenolic urethane, furan, and alkyd isocyanate. 

Schweizer M, Fear J, Cadish G (1999) Isotopic (13C) fractionation during plant residue decomposition and its implications for soil organic matter studies. Rapid Commun Mass Sp 13 1284-1290... 

Indicators of microbial activity in soil represent measurements at the ecosystem level (e.g., processes regulating decomposition of organic residues and nutrient cycling, especially nitrogen, sulfur and phosphorus). Measurements at the community level include bacterial DNA and protein synthesis. Frequency of bacteriophages is a measurement at the population level. 

In-situ infrared spectroscopy has been used in much the same fashion at TGA, but temperature profiles have been combined with monitoring changes at constant temperature. " IR spectroscopy does not yield the same direct information about the complete removal of organic residues that TGA provides. On the other hand, CO adsorption experiments performed along with dendrimer decomposition experiments provide direct information regarding metal availability. Further, IR experiments provide... 

There are numerous reports describing the allelopathic (phytotmicrobial products on crop growth, particularly in conjunction with heavy residues from the previous crop (1-5). The cause of the reduced crop growth has been attributed to the production of a variety of toxic compounds such as phenolic acids, short-chain fatty acids, patulin, and many others (6-9). These compounds may be produced directly or indirectly during the microbial decomposition of organic residues under varying environmental conditions, such as when the soil remains wet over an extended period of time. 

An assessment of the rates and duration of phenolic acid production from a residue is an important first step. Laboratory and field studies for assessing the dynamics of phenolic acid production must include considerations of the nature of the residue, soil properties, nutrient status of the system, microbial biomass interrelationships, temperature, moisture, residue placement in or on the soil, and other factors that relate to the field. Soil properties in the field are especially important when organic residues are incorporated. When soils are wet, such as those with more than -0.02 MPa water potential, oxygen diffusion is impeded and anaerobic conditions prevail, especially in soils that are high in clay content. Under these circumstances, microbial byproducts change dramatically and one result, for example, is an increase in the production of phenolic acids. Phenolic acid production is also affected by temperature (22) and soil fertility status (23). While the C H ratio of an organic residue may influence the rate of its decomposition and, hence, the rate of phenolic acid production, the... 

Crooks and coworkers, who studied Pd and Au DENs immobilized in sol-gel titania, similarly reported the onset of dendrimer mass loss at relatively low temperatures (ca. 150 °C). Pd helped to catalyze dendrimer decomposition in their system, as well. Temperatures of 500 °C or greater were required to completely remove organic residues from their materials. (10) This treatment resulted in... 

The organic treatment had higher microbial biomass C and N, enzyme activity and potentially mineralisable N (Cunapala and Scow 1998) and different microbial community composition phospholipid fatty acid than the conventional treatment (Bossio ef al. 1 998). There were minimal differences between treatments in residue decomposition (Cunapala et al. 1998). Cover crops and higher irrigation frequency in the organic treatment may have contributed to the differences (Cunapala and Scow 1998). 

Vazquez, R.L, Stinner, B.R. and McCartney, D.A. 2003. Corn and weed residue decomposition in northeast Ohio organic and conventional dairy farms. Agriculture, Ecosystems and Environment 95(2-3) 559-565. 

These definitions were essentially the same as those put forward by Berzelius. Mulder considered, however, that, besides humus substances, products from the decomposition of organic residues, such as leucine, butyric acid, valeric acid, and formic and ethanoic acids, could exist in soil. These observations are of interest because of the information that has emerged in the past half-century about growth inhibitors and stimulators from low-molecular-weight extracts from SOM and composts. 

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