ENVB 210 Lecture Notes - Lecture 17: Cellulose, Hemicellulose, Lignin
7 Feb 2018
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Soil organic matter means all type of organic material in various stages of decomposition. Humus: completely decomposed material, the constituents cannot be recognized. It is a new compound made up of microbial components, resistant plant parts and animal parts. We can (cid:862)pi(cid:272)ture(cid:863) hu(cid:373)us as (cid:373)ature (cid:272)o(cid:373)post, (cid:271)ut it is (cid:374)ot really the sa(cid:373)e thing: carbon in humus is very old and resistant to decomposition. Overall, (cid:272)o(cid:373)post a(cid:374)d hu(cid:373)us do(cid:374)"t u(cid:374)dergo the sa(cid:373)e pro(cid:272)ess. Humus has been artificially divided into 3 fractions: Fulvic acid: moves through the profile carrying fe and other metals. Tannins, lignin, waxes: resistant to decomposition (very slow) Found in older plants and trees, initially against insects. Bone and chitin (insect exoskeleton) are resistant. Majority is easily decomposable because of: c:n ratio (amount of carbon to that of nitrogen in material, bio availability of the carbone. Decomposition of organic material is done by insects + microbes (they eat it as food)
