For ideal composting to take place we wish to have C:N between 20 to 30 , generally we maintain 25. But what is the C:N of the final matured compost that is applied in the agriculture field ?
The C:N ratio of matured compost depends, beside other factors, on the initial C:N ratio of the substrate. If it is wide then the C:N ratio will be stabilized at 20-25:1 because of limited N supply. If any way N supply increases the C:N ratio may further go down. In some cases it may down up to 10-12:1. Narrowing the C:N ratio is the main objective of composting.
Perhaps our article on composting of solid wastes will be useful:
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10-12 normally, but it depends on the source of compost material. If it is a nitrogenous rich legume, the ratio comes down even around 5.
12:1 to 10: 1 but it is very dependent on source with which you started your composting process. A good book to read is Microbiology of composting it could give you better hints to solve your questions regarding composting.
I would say around C/No 12 is ideal ; a C/N of 15 can be accepted too, but there will be very probably (depending on soil type) a loss of organic matter with CO² emission due to unevitable lowering of the C/N ; however this conversion will also release some usefull nitrates and therefore support plants growth.
This value is never constant but it keeps on cahnging depending upon substrate as well as microbial activities, however any ratio below 20 is good enough for general crop rearing.
It is often admitted a C/N ratio of 12/1 or 13/1 is correct and confirms good quality of well fermented compost.
"What is C/N ration of good quality compost?" Before attempting this question directly, one should keep in mind that why carbon is an important ingredient of good fertile soil? In general, fertile soil contains more carbon substances than others due to its demand for microbial activities. That is why soil is called leaving body. See the composition (carbon content) of desert soil and compare it with forest soil. Desert soil contain 0.5% or less organic carbon where as in case of forest soil it may be anything but it is sure this should not be less than what we usually found in desert soil (> 1.0%). Coming to the question of ideal CN ratio of compost, the answer is directly correlated to why we do add compost to the agricultural filed? If the purpose is to use compost as nitrogen source the closer CN ratio (1:8-10) is advocated. If the purpose of applying compost as to improve soil health as ameliorant the wider CN ratio (1:12-20) is recommended. However the composition of compost is play crucial role, for example if the legume stuff were used for composting, the close CN ratio is but obvious, as compare to the herbage/ straw of grasses and cereals. Similarly time of compositing is also very crucial, hot summer/ rainy season compost can produced wider CN ratio as compare to the dry and cool season.
Now with this background we can easily understood what will the ideal CN ratio? Keeping in mind, the foregone discussion, now it can be concluded that the CN ratio of 1:10-15 is ideal for all purpose.
Nicely explained by Sir Anil Kr. Singh.... I totally agree with him. Thanks to Anil Sir for this elaborative answer where he explained C/N ratio for different situations.
For more details, one can crosscheck this ratio which is already explained in many literatures like:
1. Composting - Agricultural & Resource Economics - UMD.edu
PDFhttps://www.arec.umd.edu › files › _docs
2. USING COMPOST FOR GROWING VEGETABLES
PDFhttps://umanitoba.ca › afs › ncle › pdf
3. Dairy Waste Management and Composting - UMass Extension
PDFhttps://ag.umass.edu › fact-sheets › pdf
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