Changes in the chemical composition of soil organic matter after application of compost

Abstract

Summary Is the composition of soil organic matter changed by adding compost? To find out we incubated biowaste composts with agricultural soils and a humus‐free mineral substrate at 5°C and 14°C for 18 months and examined the products. Organic matter composition was characterized by CuO oxidation of lignin, hydrolysis of cellulosic and non‐cellulosic polysaccharides (CPS and NCPS) and 13C cross‐polarization magic angle spinning nuclear magnetic resonance (CPMAS 13C‐NMR) spectroscopy. The lignin contents in the compost‐amended soils increased because the composts contained more lignin, which altered little even after prolonged decomposition of the composts in soil. A pronounced decrease in lignin occurred in the soils amended with mature compost only. Polysaccharide C accounted for 14–20% of the organic carbon at the beginning of the experiment for both the compost‐amended soils and the controls. During the incubation, the relative contents of total polysaccharides decreased for 9–20% (controls) and for 20–49% (compost‐amended soils). They contributed preferentially to the decomposition as compared with the bulk soil organic matter, that decreased between < 2% and 20%. In the compost‐amended agricultural soils, cellulosic polysaccharides were decomposed in preference to non‐cellulosic ones. The NMR spectra of the compost‐amended soils had more intense signals of O–alkyl and aromatic C than did those of the controls. Incubation for 18 months resulted mainly in a decline of O–alkyl C for all soils. The composition of the soil organic matter after compost amendment changed mainly by increases in the lignin and aromatic C of the composts, and compost‐derived polysaccharides were mineralized preferentially. The results suggest that decomposition of the added composts in soil is as an ongoing humification process of the composts themselves. The different soil materials affected the changes in soil organic matter composition to only a minor degree.

Zinc forms in compost and red mud-amended bauxite residue sand

“…Reduction in pH due to higher levels of biosolid addition could be ascribed to increased mineralisation of organic matter coupled with oxidation of N and S. In addition, it could be also attributed to the reduced concentration of HCO 3 − and CO 3 2− ions in solution (Brofas et al 2000;Courtney et al 2003;Xenidis and Harokopou 2005). More than a two-fold increase in C content due to compost addition was observed in the current study and similar results reported by various researchers (Leifeld et al 2002;Weber et al 2007). Commercial compost at 50 t ha -1 produced highest organic C (0.96%) followed by biosolid mix (0.75%) and piggery mix (0.64%).…”

Carbon mineralization and nutrient availability in calcareous sandy soils amended with woody waste biochar

“…CO 2 evolved during the incubation was trapped in 1 M NaOH, the excess of which was then titrated with 0.1 M HCl after addition of BaCl 2 . Mineralized C was calculated as the CO 2 efflux rate (mg C g À1 soil day À1 ) and cumulative CO 2 -efflux (g kg À1 soil) according to Usman et al (2004) and Leifeld et al (2002). Soil labile C fraction was measured after extraction using 0.5 M K 2 SO 4 solution and oxidation with K 2 Cr 2 O 7 at 100°C and a subsequent back-titration of the unreduced dichromate (Vance et al, 1987).…”

Fusarium oxysporum f. sp. lycopersici and compost affect tomato root morphology

“…The diverse nature of the relationship between compost and plant health includes inactivation of pathogens during the process of composting (Bollen 1993), indirect antiphytopathogenic influence of compost due to modified plant growth conditions (Delschen 1999;Leifeld et al 2002) and direct suppression of plant pathogens (Hoitink et al 1997(Hoitink et al , 2001. A complex interaction between abiotic characteristics and microbial activity is proposed to be responsible for suppressive properties of certain substrates (Alabouvette 1986), though the exact mechanisms of action are still widely unknown.…”