Molecular Characterization of a Compost and Its Water-Soluble Fractions

Abstract

A sequential chemical fractionation was applied to a compost, with its dissolved organic matter (DOM) extracted in water and separated in hydrophilic (HiDOM) and hydrophobic (HoDOM) components and a water extract, following oxidation of compost suspension with an oxygen flux (TEA). The components sequentially isolated by mild extractions and hydrolyses as structurally unbound (SU), weakly bound (WB), and strongly bound (SB) to the matrix of the bulk compost and its water-soluble fractions were identified in their molecular structure. The bulk compost was rich with components derived from both aromatic (phenolic compounds) and aliphatic (long-chain fatty acids, hydroxy acids, diacids, and alcohols) structures of suberins, whereas components derived from cutins were especially extracted from TEA, HoDOM, and HiDOM. The TEA sample also yielded a significant amount of oxidized products that was dominated by dehydroabietic acids. The fractionation sequence highlighted the different intermolecular interactions that bound the isolated molecular components to the compost complex matrix. While a significant part of the bulk compost was still present as a solid residue at the end of the sequential fractionation, all water-soluble fractions were almost completely hydrolyzed. These results indicate that the water-soluble components of compost may be readily separated from the compost matrix and contribute to the environmental dynamics of natural organic matter.

Airborne soil organic particles generated by precipitation

“…Assuming >C 18 molecules (MW > 250 g mol −1 ) are dominant in mobilized SOM (ref. 18) and the O/C ratio of ∼0.4 reported here, based on the compilations of Koop et al 5 we estimate a glass transition temperature of SOM of ∼300 K. Therefore, evaporation of water from the SOM-containing mist would result in amorphous solidification (glassy state) at ambient temperatures, consistent with observations of solid spherical ASOP reported here ( Supplementary Fig. 6).…”

Seed Germination and Seedling Growth of Tomato and Lettuce as Affected by Vermicompost Water Extracts (Teas)

“…This suggests that factors beyond physical alteration of seedcoats were responsible for earlier and better germination. Spaccini et al (2008) reported that aerated compost extracts contained low-molecularweight bioactive compounds of microbial origin. Arancon et al (2007) demonstrated that the application of a vermicompost extract to growth media enhanced seed germination and seedling growth of tomatoes and cucumbers.…”

Vermicompost enhances germination of the maritime pine (Pinus pinaster Ait.)

“…Vermicompost has shown to stimulate germination of several ornamental and horticultural plant species such as green gram (Phaseolus aureus) (Karmegam et al 1999) with the solid vermicompost, thus suggesting that other factors rather than physical amelioration were responsible for higher germination. A recent study by Spaccini et al (2008) showed that aerated compost extracts contained most of the low-weight compounds associated to a compost matrix, most of them of microbial origin and therefore potentially bioactive substances. Moreover, a further study demonstrated that these extracts produced greater effects in plant physiology than the equivalent bulk compost (Puglisi et al 2008).…”