Co-accumulation of microbial residues and particulate organic matter in the surface layer of a no-till Oxisol under different crops

Lignin biochemistry and soil N determine crop residue decomposition and soil priming

“…Lignin, a complex molecule comprising up to 20 % by mass of crop residues (Johnson et al 2007;Martins et al 2012), is resistant to degradation by extracellular enzymes (Austin and Ballare 2010). Residue decomposition is generally negatively related to residue lignin content (Hofmann et al 2009;Yanni et al 2011) and lignin:N ratio (Melillo et al 1982;Wang et al 2004).…”

Allocation of photosynthestically-fixed carbon in plant and soil during growth of reed (Phragmites australis) in two saline soils

“…Particulate organic C and MAOC were separated as described by Martins et al (2012). Briefly, 50 g of airdried soil (< 2 mm) was dispersed for 16 h on a reciprocal shaker in 200 ml deionized water containing 10 glass beads (6-mm diameter).…”

“…Particulate organic C represents a substantial fraction of fresh plant residues and of plant residues at various stages of decomposition. In contrast to POC, MAOC is the residual C after POC removal and is regarded as the relatively stable C pool (Salvo et al 2010, Briedis et al 2012Martins et al 2012). However, Torn et al (2013) also report that MAOC contains a fastturnover C component, and thus it is necessary to further investigate MAOC stability.…”

“…Dissolved organic C as mobile C in soil provides energy for microorganisms and is adsorbed by soil particles (Kalbitz et al 2000), and dead microorganisms release DOC or form the relative stable pools (Kalbitz et al 2003). Soil microorganisms can attach to soil particles (Nicolás et al 2014) and also utilize C sources from soil particles (Six et al 2002;Martins et al 2012;Torn et al 2013;Keiluweit et al 2015). Overall, DOC, MBC, POC, and MAOC together represent the chemical, biological, and physical forms of SOM.…”

“…Consequently, the duration of root-deposited C in the earlier pulses will increase on the final day. Particulate organic C is labile organic C and is mainly derived from microbial debris and root residues (Briedis et al 2012;Martins et al 2012) but MAOC is relatively resistant organic C and plays a key role in preserving the soil organic C content (Angers et al 1997;Six et al 2002;Zeller and Dambrine 2011;Briedis et al 2012). At end 6-h the disappearance of PO 13 C in HS soil (Fig.…”