Role of Humification Processes in Recycling Organic Wastes of Various Nature and Sources as Soil Amendments

Abstract

Recycling the large amounts of organic wastes produced by agriculture, forestry, urban and industrial activities as soil, organic amendments are the most popular and efficient option for avoiding their dispersion in the environment and restoring, maintaining, and/or improving the content of soil organic matter. Chemical stability and biological maturity are two important factors for the successful use of organic wastes in agriculture with limited risk for the surrounding environment. Stabilization and maturation of raw organic wastes inherently imply the achievement of an extensive humification, that is, a wide conversion of easily degradable organic matter to refractory organic compounds that resemble native soil humic substances (HS). Soil HS are the most important components of soil organic matter responsible of several soil functions and processes. As a consequence, the amount and quality of HS‐like fractions in any organic amendment are believed to be of primary importance for its agronomic efficacy, environmental safety and economic value. The first part of this review focuses on the chemical and physico‐chemical changes occurring in the humic substances (HS) ‐like fractions of organic wastes of various nature and sources subjected to common treatment processes aimed at producing environmentally‐safe soil amendments with beneficial agronomic properties. The second part discusses the composition, structure, and chemical reactivity of the HS‐like components in organic amendments of various origins and nature, and their effects on native soil HS. The review concludes by highlighting the need for innovative research targeted mainly to achieve a better fundamental understanding of the molecular structure and reactivity of soil HS and HS‐like fractions in organic amendments, the mechanisms of HS formation and transformations in the natural environment and during the treatment processes of raw organic wastes, the interactions with metals and organic xenobiotics, and the direct physiological effects that HS may exert on plants.

Effect of using some soil conditioners on salt affected soil properties and its productivity at El-Tina Plain area - North Sinai - Egypt.

“…were 5.06 and 5.17 %. The positive effect of biochar on reducing soil pH values may be due to the acidic materials produced from the oxidation and decomposition of such material in soil (Senesi and Plaza, 2007; Dias et al, 2010). Biochar is not at all inert in soil and can be oxidized, especially at the surface, through chemical and microbial activity (Cheng et al, 2006(Cheng et al, , 2008.…”

Influence of the composition of the initial mixtures on the chemical composition, physicochemical properties and humic-like substances content of composts

“…The humification process leads to the formation of com-pounds with increasing molecular weight, concentration of oxygen (carboxylic, phenolic, ethers and esters groups) and nitrogen (amides groups) containing functional groups and aromatic characteristics (Ait Baddi et al, 2004;Senesi, 1989;Senesi and Plaza, 2007). Therefore, methods capable of detecting these functional groups, such as FT-IR, have been employed to follow the humification process in composts (Ait Baddi et al, 2004;Amir et al, 2005Amir et al, , 2010Shirshova et al, 2006;Smidt et al, 2008).…”

The role of organic amendments in soil reclamation: A review

“…More recalcitrant, lignin-rich amendments, such as woody biomass and possibly pulp and paper mill sludge, are less labile in the soil and will usually show a smaller but longer-lasting effect on soil properties. Microbial oxidation of lignin to polyphenols is considered one of several pathways in the humification process (Senesi and Loffredo 1999), leading to formation of recalcitrant organic carbon that will contribute to longterm carbon stabilization.…”