SOIL 3600 Lecture Notes - Lecture 23: Humus, Chemotroph
Document Summary
If c/n ratio low - n may be released to soil: both c & n are essential to life - both s and n are needed for energy and growth. Definitions: heterotrophic micro-organisms - obtain energy by decomposition and metabolism of organic compounds, feed on green, with poly get sta(cid:271)le hu(cid:373)us, autotrophs - obtain energy via breakdown of inorganic compounds, e. g. Photoautotrophs, chemoautotrophs: note that since c and n needed for life - there is a close relationship between them --> c/n ratio. C/n ratio and soil mineral n diagram: when organisms die - release n back to soil, during organism use of n - no available. Starting conditions: modest level of nitrate, low c/n ratio, low microbial activity. If cn ratio of substrate (residue) is >24, microbes steal from soil. If cn ratio < 24, net mineralization of n.