Soil organic C is known to be protected by three main processes in soils - chemically, physically, and biochemically. Among the biochemical characteristics of an organic material, C/N is among the ones that show a great influence on its decomposition rate. A material with lower C/N ratio, like soybean residue, compared to a corn residue for example (higher C/N), would be much easier to be decomposed by the microorganisms, being known as a more labile material. But an interesting fact showed recently by a group of researchers is that the stoichiometry of the organic material being decomposed is determinant on how much CO2 would be released during decomposition. The microorganisms have a fixed nutrient ratio (C/N/P) and, during the decomposition process they impose its own stoichiometry to the transformed material. It means that, a diet rich in C causes microorganisms to release more C as CO2 into the atmosphere as the microbes try to maintain their healthy C/nutrients ratio. You might want to check out the following papers.

Manzoni et al. The Global Stoichiometry of Litter Nitrogen Mineralization. SCIENCE, 2008.

http://www.sciencemag.org/content/321/5889/684.short

Manzoni et al. Stoichiometric controls on carbon, nitrogen, and phosphorus dynamics in decomposing litter. ECOLOGICAL MONOGRAPHS, 2010.

http://www.esajournals.org/doi/abs/10.1890/09-0179.1?journalCode=emon

Yes, Organic matter decomposition is surely dependant on C:N Ratio. If C:N is around 1:11 decomposition of O.M is efficient and good enough and it is reduced or inhibited both when this C:N ratioo is narrow or wider.

Yes. Since organic matter decomposition is part of soil microbial activity, thus require N as their nutrient; thus soil organic matter high in C:N ratio can decompose more rapidly than lower C:N ratio OM.

Yes. For example, an important reason for the low decomposition rate in boreal bogs is that the ecosystem is very N poor.

Soil organic C is known to be protected by three main processes in soils - chemically, physically, and biochemically. Among the biochemical characteristics of an organic material, C/N is among the ones that show a great influence on its decomposition rate. A material with lower C/N ratio, like soybean residue, compared to a corn residue for example (higher C/N), would be much easier to be decomposed by the microorganisms, being known as a more labile material. But an interesting fact showed recently by a group of researchers is that the stoichiometry of the organic material being decomposed is determinant on how much CO2 would be released during decomposition. The microorganisms have a fixed nutrient ratio (C/N/P) and, during the decomposition process they impose its own stoichiometry to the transformed material. It means that, a diet rich in C causes microorganisms to release more C as CO2 into the atmosphere as the microbes try to maintain their healthy C/nutrients ratio. You might want to check out the following papers.

Manzoni et al. The Global Stoichiometry of Litter Nitrogen Mineralization. SCIENCE, 2008.

http://www.sciencemag.org/content/321/5889/684.short

Manzoni et al. Stoichiometric controls on carbon, nitrogen, and phosphorus dynamics in decomposing litter. ECOLOGICAL MONOGRAPHS, 2010.

http://www.esajournals.org/doi/abs/10.1890/09-0179.1?journalCode=emon

Rosa Francaviglia ,A.C. Preger ,Pier Paolo Roggero,Pier Paolo Roggero ,Leonardus Vergutz ·,Guntur Subbarao ,Riazuddin Ahmed al of you thank you for your guidance. But one question in mind is when the decomposition of material in the soil at that time some becterial group can eat some essntial food material which is reqired for the crop and at that time nutrition of that plant not takes properly. Then question arises that, Either completely decomposed material is incorporated in the soil is better or whose C:N ratio is higher than 30:1 . Coz the great scientist Fukuoka says u can incorporate wood material in the (C:N ratio of that material is 100:1 or more) soil he can give better reply.... then what is true C:N ratio higher material can made nutrient deficieny for crop or C:N ratio less material can give proper nutirition to the crop. Can you explain this?

It is a very interesting question. May I give the results out of my experience and perception.

In a very broad sense C:N ratio of organic matter 'matters', however a clear cut and explicit elation one can not expect. The organic matter is not just one compound. That is the fundamental principle borne in mind when we approach this issue. Unfortunately, all over the world soil scientists still hold on to just one point that simply organic carbon can represent all of the thousands of C compound present in soil which are basically different in its chemical nature and structure. Essentially we should note the chemistry of the compound before arriving at a conclusion. Just imagine the case where the lignin or chitin or tannic Carbon is similarly treated with the sugar or cellulose or starch Carbon. The decomposition is a process greatly depending on the activity of micro organisms and the nature of organic C and its vulnerability towards microbial activity. Hence the structure and nature of Carbon compounds in soil need to be ascertained, then only a real picture on decomposition can be assessed. A lot of literature available in this area. please refer one of my papers in Plant and Soil (2008) 303 : 265-273.

Hope an area of interest is openend for further research to you.

Thanks

There is definitely a close relation between organic matter decomposition state and C/N ratio. But it is more correct to say that C/N reflects, or constitutes an indicator of the organic matter decomposition degree, than to say that the decomposition depends on C/N ratio.

Interesting to raise the ideas of Fukuoka. The thing with added materials with C/N ratio is, that it will immobilize nitrogen. That is the reason to add enough 'brown' material in a compost heap. Mixing wood or straw in the soil will definitely affect the N nutrition of your crops negatively. Therefore, In the fukuoka and permaculture practises, such high C/N ratio materials are added on top of the soil. This will ensure that N is only immobilized in the litter layer. From my own experience at home, adding such a layer of high C/N will speed up the microbial processes in the mineral soil below (energy source). Not sure if it will have a net effect on the carbon stock in the mineral soil, but the crop plants do not have shortage of N.

Regarding to the N dynamics in the soil, you have to take into account the food web as well. Bacteria have a low C/N ratio, while feeders on bacteria have a higher C/N ratio. Thus, predation of bacteria lead to a net mobilization of N (exuded by the predator). So, it is not just C/N ratio and SOM, but also the food web that determines the N dynamics (plus of coarse all the mentioned physical and chemical SOM protection mechanisms).

if organic matter is more when C/N 30:1 than imobilization process will be increased but when C/N ration is < 1:20 mineralisation process will be increased and C/N ration Belween 20-30:1 nither imobilization nor minerlization process will not takes place

Third question derived from Sujit....

All this is a balance of fluxes & pool.

If you want to produce crops you need to have low C/N ratio in organic residues, soil neutral pH, high temperate & good soil content, etc., because you need fluxes (in special, of N).

I you want C sequestation you need to create a big pool, no fluxes; then, you need to add organic residues with high C/N ratio, acid soils, low temperature, dry season, etc.

Conclusion: It is very difficult to produce crops AND to sequester C; you need to equilbrate both processes, to have fluxes and to create a permanent C pool in soil.

Pardon: ..., high temperature and good soil water content....

The wider C:N ratio of the material (manure or organic residues) is indicative of the more quantity of carbonaceous material and this will take more time to decompose.

I haven't been here for a while but as your question is about a possible deficiency for crops, it's well known that if you add C rich material to the soil (high C/N) it will cause a temporary N immobilization, in order to the microorganisms to metabolize this material. Thus, the N shortage will be worst depending on which type of crops you are planting. If they are perennial, the plants will feel it, but they also will have time to absorb N when the immobilization period ends and mineralization starts to take place. But if you are planting annual crops, which have a really short cycle, they won't have time to reach the mineralization period and the N deficiency for these will be severe. It's all about the frame time. This is well known for N but recently experiments have shown the same for Ca, specially in planted forests.

YES. The C:N ratio essentially influences the OM decomposition. The C:N ratio has an inherent tendency to stabilize at 10:1 at the end of OM decomposition. It becomes wider on addition of fresh undecomposed organic materials. The N immobilization is a necessary evil if not a N conservation mechanism to prevent gaseous loss of nitrogen in to atmosphere. The ultimate objective of OM decomposition is to improve and maintain humus content of soils for their greater productivity for which soil biota have a pivotal role.

Thank you Mr.Michael for a wonderful addition to improve the efficiency of N. N:S ratio is always a favourable parameter to prevent N losses by volatalization. There is also N:P:S ratio which further stabilizes the decompostion thereby preventing losses of these precious nutrients. Addition of S rich vegetation belonging to Cruciferaceae family and certain grains would improve S and P status and in turn the C:N ratio.

Decomposition of organic mater is largely depended on C:N ratio. You know that this decomposition is carried out by micro-organisms (as bacteria, fungi, actinomycetes etc.). They decompose these OM because they need org. C for their food source and body building (as being heterotroph). But they need not only C but N also (other elements are also required as S). That's why they prefer N rich material. For bacteria is estimated that for every 3 part of C they need 1 part of N. So more is the N i.e. (lower C:N), better and quicker is the degradation.

Now in soil with applied OM, if the organisms did not get N in the degrading material they will derive the N from soil itself making the soil poor in N in a short term. As they died the N is available again in soil. So for crop land it is advised to apply OM with lower C:N ratio. Otherwise the crop itself will suffer from N deficiency.

Under lab condition where the organic matter is the sole source of energy and nutrients, C:N ratio is the single most determining factor for OM decomposition with low ratio more decomposition. But in soil decomposition of OM is not much dependent of the C:N ratio of OM rather it also depends upon the N availability in soil. When OM is added in soil, based on C:N ratio of the OM two processes mineralisation or immobilization of soil N occurs. If C:N ratio of OM is 30 then immobilization will occur and in between 20-30 there will be an equilibrium with no net mineralization or immobilization.

Organic matter should be treated as food for soil biota instead of considering it as a material to improve fertility status of soils. With this view, we would be careful to apply organic matter which is easily decomposable with optmum moisture content so that the microbial and macrobial organisms need to exert least energy to feed on to ultimately to break down the material in to humus.

The C:N ratio essentially influences the OM decomposition. The C:N ratio has an inherent tendency to stabilize at 10:1 at the end of OM decomposition. this is for simple reason, Microorganisms, also need nitrogen to live. Fungal cell commonly have C/N ratio of about 10, and bacterial cell commonley have C/N ratio of about 4. If C:N ratio of OM is 30 then immobilization will occur and in between 20-30 there will be an equilibrium with no net mineralization or immobilization.

Do not forget effects of contamination/pollution. If you have a low C/N ratio (e. g.,

Actually I agree to all of the explanations. I only would like to add that C/N ratio is dependent upon the chemical composition of natural organic matter (NOM). In particular, the larger the N amount due to presence of, e.g., hydrophilic amino acids/oligopeptides, the lower is the C/N ratio, thereby leading to faster NOM mineralization. In fact, large content of hydrophilic N-containing materials enhance microbial activity and NOM decomposition. As NOM is decomposed, nutrients become available for plant nutrition. However, according to Juan Gallardo Lancho, if the C/N ratio is affected by N-containing pollutants undesirable effects may occur. Moreover, very low C/N ratio values may lead to OM soil losses and to desertification problems. That is the reason why a C/N ratio of around 25 is considered optimal for soil fertility. As C/N becomes 50 then problems arise. Only the C/N ratio value cannot be sufficient to establish the optimal conditions for soil fertility.

The C/N ratio is important in determining the compost stability and maturity. However, tThere is no general agreement which value of the C/N indicates maturation of compost. Indeed, the interval of the optimum C/N values is between 8 and 15 for Mustin (1987), ranges between 25 and 35 for Ryckeboer et al. (2003) yet it oscillates between 25 and 40 as it was reported by Baldwin and Greenfield (2009) and composting. Raj and Antil (2011) have reported that a value of this ratio inferior to 20 and even 15 characterizes mature compost yet a stable one is characterized by a ratio comprising between 10 and 15 (Albrecht, 2007). Dayegamiye et al. (2005) noted that this ratio must be inferior to 30 yet Zbytniewski and Buszewski (2005) have reported that a C/N ratio of about 15 expresses stabilization of composting mass and one below 12 indicates a high degree of compost maturity. However, Komilis and Tziouvaras (2009) sew that a C/N ratio of 10 has been alleged to characterize mature composts.

I did not get a good correlation between C: N ratio and other techniques such as electron paramagnetic resonance and laser induced fluorescence.

EPR actually allows measurement of paramagnetic properties of organic and inorganic materials. Why do you think that a correlation must exist? Usually paramagnetic properties are related to presence of condensed aromatic rings with very mobile electrons. C/N ratio measures the amount of hydrophilic systems usually referred to as aminoacids and proteins (also oligopeptides). They do not show paramagnetic properties.

For what concerns the fluorescence activity, the same consideration must be done. In fact fluorescence is a characteristic for aromatic systems. the larger the polycondensation degree of the aromatic systems, the larger is the fluorescence activity. Amino acids and proteins/oligopeptides are not fluorescent, unless you do not have a huge amount of aromatic aminoacids.

You may find such correlations only if you think that you have heterocyclic nitrogen atoms in polycondensed aromatic structures.

yes om decomposition is dependent on C:N ratio..

Thanks for your reply Dr. Pellegrino Conte. I'm thinking about...

Some studies, such as in Martins (2010), has found very good correlation between the C:N ratio and humification evaluated by FIL. What does this mean? Is this just a coincidence?

Thank you very much

http://www.sciencedirect.com/science/article/pii/S0167198710001972

In coastal and marine sediments, organic matter with a lower C:N ratio typically originates from local production (autochtonous) and is more reactive than organic matter delivered from the continents (allochtonous). Low C:N ratio organic matter is typically more reactive because it contains more N-rich molecules (proteins and amino acids) which are more nutritious to bacteria (and likely yield a greater amount of energy per mole of C metabolized).

According DUCHAFOUR's and also BERG's ideas C/N ratio of the organic residues only has influence at short time in the humificaction process; after a period (depending from climatic conditions), other fractors (climate, bases, clay content, etc.) drive the process to the total mineralization (or humification, parallel processes).

Any way, as said, high C/N ratio usually produces CO2, but low C/N ratio can contaminate the system for leaching of nitrates (not absorbed by plants).

Discussions are very interesting.

I think organic matter decomposition depends on the stuctural charateristics of organic matter, microbial community as well as the availability of the organic matter to the microorganisms.C/N ratio is a good idicator for orgnic matter degradability. However, the critical C/N value may differ from both the property of OM and the environment for microorganisms to access OM. I may suggest you to read Schmidt et al.2011. Persistence of soil organic matter as an ecosystem property. Nature 478, 49-56.

Best ratio narrow such as 30/1

If my reading is correct there are two main currents in the response up to now. In one, the answer centers in litter (or other residues) decomposition, and these tend to enhance the C:N paper in the decomposition. The other main line concerns mostly stable or semi-stable soil organic matter, and these tend to the view thatC:N isn´t a major factor.

Coming from the decomposition side of the aisle, C:N tends to be one of the major aspects of litter quality, but it should not be considered by itself. For example, some of our studies here in Brazil have indicated that legume residues with lowish C:N ratios (about 20-30) have decomposed slightly less than pure grass residues with initial C:N of up to 50. It seems that lignin content becomes the major determinant of initial decomposition, above a certain (as yet unstudied) threshold.

These are as yet unpublished, and part of a PhD thesis which will be defended by one of my advisees this month, so I can´t point you to the exact data, but those are the main lines. Of course, with this kind of data, I would advise taking my information with a pinch of salt, but the data seems promising.

Also of course, this has two main aspects: first it may reduce short term value of the litter in terms of nutrient cycling since lower decomposition means lower biologically N fixed coming into the system; on the other hand, if it goes on for longer than the 256 days we studied, it could lead to an increase in stable organic matter, with all kinds of consequences from a greenhouse effect point of view. Again, this data should be considered as preliminary and short term, but it seems that this may be an interesting avenue to pursue.

Decomposition is greatly affected by the C:N ratio of the litter

The C:N ratio is commonly used to describe 'litter quality' along with lignin content and can affect the initial rate of decomposition of litter and final residue; e.g. see

Berg B (2000) Initial rates and limit values for decomposition

of Scots pine and Norway spruce needle litter: a synthesis for

N-fertilized forest stands. Canadian Journal of Forest Research,

30, 122–135.

Yes

Ratio have an impact on the activity of soil organisms

Low percentage is the best

Such as 20:1 or 30:1

Ratio have an impact on the activity of soil organisms

Low ratio is the best

Such as 20:1 or 30:1

Figure 14 of attached chapter illustrates how C:N ratio of the more labile SOM fraction relates to N realease (ie SOM decomposition).In this case N release occurs when the labile pool C:N ratio is below 22:1

Definitely there is impact of C:N ration on decomposition. Lower the ratio and higher will be the decomposition. For examples, plants have high amounts nitrogen content and faster will be the decomposition rate.

C:N ratio is definitely an important factor in organic matter decomposition. However, moisture and temperature availability is even more important factor. In conservation farming where you have a huge amount of crop residues present, a good C:N ratio creates a better condition for organic matter decomposition provided that you have adequate moisture and temperature.

Yes, but other nutrients as P should be found in enough available concentrations in soil for stimulating the microbial decomposition for the organic matter

Yes, C:N ratio is one of the major determinant of organic material decomposition in the soil. Many of the scientific reasons adduced for this has been mentioned by earlier contributors.

Leonardus Vergutz

I agree you!

If you talk about soil, the answer is as usual not unique.

A citation classic in this sense is Fog (1988), but still more recent papers (e.g. Knorr 2005) are not so distant from that one. The answer is of course: it depends.

It depends from where you are, basically, including the local nutrient conditions and the other stabilization mechanisms effective in your environment.

As a general "law", Knorr notice that decreasing the C/N ratio (increasing N) stimulates decomposition for high-quality (low lignin) substrates and in case of systems with low ambient N deposition, while the opposite was true with high N deposition levels and for low-quality substrate.

But I suggest you to search extensively in the literature to find a study that might be close to your environment, and then try to understand the possible causal connections you might have with edaphic factors. The C/N ratio is a really powerful (meaning effective) indicator related to decompositiona lso because it is quite syntetic and infuences (and it is influenced) by a lot of factors, and can be just a high-level answer to your research question.

Fog, K. (1988). The effect of added nitrogen on the rate of decomposition of organic matter. Biological Reviews, 63, 433–462.

Knorr, M., Frey, S., & Curtis, P. (2005). Nitrogen additions and litter decomposition: a meta-analysis. Ecology, 86(12), 3252–3257.

If the C / N ratio of organic material added to soil exceed about 25 / 1, the soil microbes will scavenge the soil solution to obtain enough nitrogen. Thus, the incorporation of high C /N residue will deplete the soil’s supply of soluble nitrogen, causing higher plants to suffer from nitrogen deficiency. So with increasing C/N ratio, decreased soil organic matter decomposition.

Yes, C:N is one of foremost factor in decomposition of organic matter. the rate of mineralisation and immobilization of nutrients is depend up on C:N ratio only. When C:N ratio is higher than optimum, there is immobilization process will dominant and vice-verse. If Om has low C:N (4:1), decomposition and it is high, slow rate & immoblization process become dominent example, maize straw (>80:1).

The C:N ratio keeps on changing and it is a dynamic process controlled by moisture, temperature, aeration, quantity and diversity of organic matter, decomposition rate, microbial density and diversity. Narrow ratio is favourable to rhizosphere since it becomes stable. Addition of organic matter with narraow CN ratio is a good practice for soil development.

Certainly yes, C/N ratio of the material is the key factor for successful compost production. The topic has been extensively investigated, thus number of research findings are available covering many aspects

Wish to express my appreciation to all for providing their viewpoints. As a professional soil/compost microbiologist and life-long composter/farmer-gardener, my 'take' on C:N is a bit different than most of you, Your patience is solicited as I attempt to phrase my input from a layman's perspective rather than a technical one - since hopefully there will be some non-technical farmers/gardeners watching this tread that need to understand some basic C:N methodologies in the effective practice of utilizing their crop/livestock residues to enhance their soil/dirt in order to enhance their crop yields while lowering their use of synthetic chemical pollutants (and associated costs).

Certainly multiple sciences (physics, chemistry & biology being foremost) are involved in the decomposition of organic MATERIAL into organic MATTER and thence into HUMUS (compost is NOT Humus, although if properly managed, can contain a high proportion of it - in its well-aged state) - Humus being the FINAL amphorous (without shape/form) result of microbial activity - one of the most complex carbon-chains known to science (science does not have that chain 'figured-out' yet).

Several of my learned colleagues have already given the "correct" answer to the C:N question - which in my opinion is: DEPENDS.

Depends on a HUGE number of factors (more than are noted in this offering) such as the type/mix of feedstocks (each having their own C:N ratio dependent on time/age of the material as N volatilizes/leaches); percent of moisture (specifically the dissolved oxygen content available to microbes IN that water; (microbes don't 'breathe' air like humans - and someday the commercial composting industry will 'wake-up' to that fact - but I empathize with them, because the composting industry is severely hampered by antiquated, un-scientific State regulations that are (for the most part) NOT based on current science; and IN THE END, the C:N 'answer' is dependent upon the MOST IMPORTANT aspect - the density and diversity of the microbial community (the individual needs of the bacterial/fungal/ [and in some cases protozoan] communities) that actually perform the saprophytic decomposition work.

It is VERY difficult for ANYONE (even researchers/scientists) to estimate the actual C:N ratio of even a single large quantity of the same feedstock (without using complicated lab testing) - much less a mix of multiple feedstocks because each individual ratio (ergo the total) can change DAILY. MUCH too complicated for the people who actually must perform the activity of bio-degrading their organic residues. Fact is: one uses what one has to work with. The objective then, is to enable/facilitate a given (mix of) feedstock to be 'eaten' by microbes - (technically the microbes themselves don't physically 'eat' feedstocks - the ENZYMES they produce do that) and it takes a 'community' of microbial enzymes to perform that function efficiently.

So permit me to offer some suggestions for utilizing C:N based on a compilation of my lab work AND practical in-the-field experience:

1) By whatever means available, reduce the PARTICLE SIZE of 'whatever' feedstocks are used when in their 'dry' state by grinding/chopping/shredding or whatever way possible. As SMALL as possible. This is the single MOST important activity in composting because it can actually CHANGE the C:N ratio from its original large-particle ratio. SURFACE AREA available to MICROBES is KING of Composting OR amending soil/dirt with organic material by ANY method. If at all possible, create a homogeneous MIX of multiple feedstocks first.

2) C:N ratio is ONLY RELEVANT to saprophytic decomposition at the MICRO LEVEL. And with the naked eye, NOBODY can tell what's "in there". And also, DON''T depend on the EXISTING microbial community that is 'hitching a ride' on the given type of feedstock.

Instead, INOCULATE the FULL COMMUNITY of LIVE beneficial microbes (DORMANT microbes do NOTHING to enhance rapid decomposition). To do that, use a BLEND of VERY high-grade AGED (or at least MATURE) thermal compost and vermi-compost (earthworm castings) - verified by microscopic direct observation at 400x - along with an C:N ACTIVATOR formula to ensure microbial reproduction - to make an in vitro (in a tank) Liquid Microbial Concentrate (LMC - commonly referred to as 'compost tea') at MINIMUM aeration of at least 6ppm dissolved oxygen and at MINIMUM period of 24 hours. Do NOT try for longer 'brews' unless you're QUITE experienced in developing microbial concentrates.

The Internet is FULL of compost tea 'how-to' information - which, in my opinion, MOST is 50% MYTH. It's easy to make 'BAD' tea - harmful to a plant-growth medium and 99+% of the people who make 'tea' don't have it lab-tested - so they DON'T HAVE A CLUE to the efficacy of the brew they make. So be careful who you choose to believe. In my opinion, Dr. Elaine Ingham (Chief Scientist at Rodale who developed multiple AACT Activator recipes) is closest to my own mind-set.

3) PRE-MOISTURIZE the reduced-particle feedstocks (if feasible, even SOAK the feedstocks for a short time in a AERATED [8-12ppm DO] bath with a liquid C:N ratio FEEDSTOCK ACTIVATOR solution to which the final LMC 'brew' has been added into a 3:1 volume of non-chlorinated (or de-chlorinated) water . If you SPRAY this Feedstock Activator, do so in a manner in which the leachate can be collected and re-used (don't waste it - a VERY valuable residual). Most Feedstock Activators have a base of amino acid (proteins - the N factor) and simple sugars (almost-pure carbon in the form of carbohydrates - molasses being the most commonly used because it's already a 'liquid', but there are others in dry form) and will ALSO contain (in liquid- usually chelated form) C, N, P & S as macro ingredients, K, Ca, Mg, Mn & Mg as Micro ingredients, and tiny amounts - any other (and some Activators contain all) Trace minerals. Soluble N,P,K + Micro/Trace fertilizers are also available to enhance such Activators - but BE CAREFUL - most soluble UREA-BASED chemical fertilizers sold at RETAIL contain very high-SALTS - which are VERY damaging to saprophytic microbial decomposition. M*G may work great for certain plants - but I don't recommend it for growing microbes.

4) Then compost or till-under the feedstocks as your methods dictate. Personally, I prefer to actively manage compost decomposition very rapidly - THEN amend sol with it - instead of putting it underground to 'fend for itself'. That way I KNOW (at 400x) what the Microbial/Humic result is - before using it to improve my soil/dirt. For the laymen who might read this post, the two most important reasons to microbially decompose organic material into matter/humic compounds are:

A) PLANT NUTRIENT CYCLING - putting organic materials into soil/dirt directly is not the best/fastest way - UNLESS the full beneficial microbial community is already in place to decompose it underground in aerobic conditions - but tilling has been proven to increase erosion - and not all the organic material gets underground.

Natural plant food is Microbe POOP - pure and simple. If one puts manure underground (decomposition of organic matter above-ground is VERY SLOW), plants CANNOT uptake the nutrients in it UNTIL microbes decompose it (albeit most manure contains a tiny bit of readily-available nutrients already - but not much, since a healthy animal will have assimilated most of them in its intestines).

B) PLANT DISEASE CONTROL - (both as foliar and root-drench treatments) - diseases are caused by pathogenic microbes. Beneficial microbes control pathogens - except wherein conditions (usually anaerobic) allow propagation of pathogens beyond ability of aerobic beneficials to control them. If that were not Nature's Way - plants AND the human race would be extinct. Think about that...

To the extent that a given C:N ratio exists - at the MICRO level - by which microbial reproduction is enhanced - YES - C:N is a VERY important consideration - but is NOT a more important factor than:

1) the dissolved oxygen content available IN MOISTURE. A DRY "perfect" feedstock C:N ratio material will NOT decompose for a LONG time and using anaerobic (deep pond bottom-water) is potentially harmful.

2) the existing microbial COMMUNITY that will reproduce to the degree needed for rapid decomposition to occur. Saprophytic microbes are generally viable in good (aerobic) water and dormant/useless in dry conditions - and either dormant or viable, most saprophytic microbes tolerate a WIDE range of temperatures.

Quite an extensive recommendation you have here Robert, but i would like to ask if there is any information on the cost effectiveness and sustainability of these options if applied to the agricultural sector.

Azubuike,

Regarding SUSTAINABILITY:

Comparatively, organically improving cropland and crops with live biological treatments resulting from organic recycling is certainly sustainable (renewable) - whereas use of agricultural synthetic chemical treatment derived from crude oil processing - is not sustainable in the long-term (at some point in the next century, oil reserves will become severely depleted) nor in the short-term.as the price of crude oil continues to drive the ever-increasing cost of food/forage/fiber crop production - borne by consumers - to whom, in this present economic time, presents a tenuous situation - particularly to low & fixed income households.

Another sustainability issue is the rampant global pollution of soil and water resources by long-term overuse of synthetic chemical fertilizers - along with severe erosion issues caused by a number of reasons - including the loss of microbial soil community from application of biologically-damaging chemicals to both plants and soil.

Regarding COST-EFFECTIVENESS:

Cost-effectiveness is certainly the bottom-line issue for the plant production (agriculture and horticulture) industries and the commercial composting industry that serves both those sectors.

Certainly the world populations need to become more aware of the need to do a better job of recycling organic resources instead or burning or burying them. Returning organic material to the earth (in one form or another) to replenish the biological component in soil can most certainly be done cost-effectively (use of time, energy and money - to increase crop harvest volume and nutritional quality - regardless of scale. A matter of innovation - the mother of invention...

By using the word 'information' rather than 'data' or statistics' I presume you are asking how much each of those options I presented - cost to implement? Both capital expense and operating costs are a matter of scale - so the answer you seek depends on identifying that scale.

I do not know the extent of your expertise in this arena, but as a aquatic toxicology PhD candidate, I will assume a lack of basic saprophytic microbial process understanding - so PLEASE do not be offended by my very basic explanation if you are more skilled in composting than I surmise.

Since you did not provide any specific example, allow me to present one broad example in the interest of directing your question toward specific answers:

PARTICLE SIZE REDUCTION:

The purpose of reducing organic material particle size is to expose greater surface area to immediate microbiological decomposition, thereby significantly speeding the process - time is money. At the horticultural level, the most common tool is a machete - which involves mostly time and physical energy. At the small farm level, a small machine should accommodate the volume (the most common machine in that category is a hammermill chipper/shredder - the size/power/cost of which is relative to volume of material needing to be processed over time). For larger operations a number of machines (such as Tub Grinder) are commercially available and are only cost-effective when needing to consistently process a large volume of material - so again - a matter of scale.

How small a particle is needed? That depends on the cost of particle-size reduction in relation to the speed at which one desires the end result to be accomplished.

PRE-TREATING ORGANIC FEEDSTOCKS:

whether particle-reduced or not - pre-treating is a means of providing a sufficient C:N ratio TO MICROBES for the purpose of their reproduction - to produce enzymes in sufficient quantity that act to solublize the feedstock at the cellular level that can then be taken up by microbes. How much a pre-treatment would cost depends on what kind of feedstock is being used.

HIGH-CARBON FEEDSTOCK EXAMPLE:

Lets say that a number of trees (roots/trunk/branches/leaves) have been processed by a machine (**capital & operating costs relative to scale) resulting in wood chips and leaf litter. Given an arbitrary C:N ratio average of 400:1 for the purpose of discussion, let's say that the pile of wood chips/litter is accumulated in a 50-cubic yard inverted cone pile directly from the particle-reduction machine.

Now we can evaluate what it would take to analyze cost-effectiveness against the cost of a given present operation producing the same quantity of woody feedstock.

PROCESSING ALTERNATIVES (as I see them):

1) assuming the pile of wood chips will sit, unattended for an extended period

a) in the open air/weather, uncovered, subject to a unknown volume of rainfall

decomposition rate will depend on moisture content first (not C:N)

My experience is that with 30 inches annually, decomposition will take place

very slowly on the periphery for' a number of reasons - not related to

moisture - and almost not noticeable on dry pile material.

b) inside a covered structure or outside covered

almost no decomposition will take place over an extended period of time,

due to the lack of moisture

2) so - moisten wood chip exterior with a water spray prior to piling

a) cost of a water pump and water along with very little labor expense

some decomposition will take place - but very slowly since the saprophytic

microbiology that decompose such high cellulose/lignin material requires a

significant amount of nitrogen to reproduce - and significant loss of moisture

will occur due to evaporation using that method

3) add a source of organic nitrogen to the water spray - let's assume use of fish

hydrolysate (not emulsion with oils extracted) - which will act to reduce

moisture loss somewhat - depending on % humidity, ambient temperature

and heat generated in the pile by thermophilic activity

a) at the rate of 2 ounces/gallon (cost relative to location & purchase volume)

a greater rate of decomposition will take place depending on how much

water is ABSORBED (not evaporated) into material via the spray application

method

However:

4) instead of spray application,, let's say that the wood chips are significantly

moistened to the extent that internally-absorbed moisture is not going to

greatly suffer from evaporation

a) through a machine-operated water bath - perhaps in the manner that potato

chips are commercially machine-cooked in oil

b) soaking in a vat for a longer period of time - greater absorbtion at less capital

expense but more labor intensive - cost relative to scale

In this instance, water/nutrient absorption into the cellular structure of the

cellulosic material increases proportional to the time that material is allowed

to absorb water - the longer the better, since the depth into material that

microbes can penetrate requires water to that depth - because microbes

derive oxygen needed to reproduce from water (not air per se). A drain-able

tank will cost much less than a mechanized soaking operation.

5) then in addition to the nitrogen-laden water, it is also highly aerated

a) thereby increasing the dissolved oxygen content of the water absorbed into

woody material. Then microbial reproduction will be greatly increased. The

means to accomplish such aeration to minimum DO requires capital expense'

to obtain/install a regenerative air blower of sufficient air flow capacity

b) but at this point, microbial reproduction will only occur at the rate

dependent on the density (quantity) of microbiology that exist in the woody

feedstock capable of decomposing woody cells - not all biology does that.

6) so to the highly-aerated nitrogen-laden water bath let's add:

a) a high concentrate of the full LIVE soil foodweb microbiological community

(compost tea) - to significantly increase the availability of cellulosic-

decomposing microbiology - thereby ensuring greatly-enhanced reproduction

7) then let's add a composite of enzymes formulated to act on cellulose/lignin

material - thereby increasing the rate of immediate decomposition by

solublizing material for immediate use by microbes as food - rather than

waiting for the microbial population to produce those enzymes - however, an

enzyme 'package' can be expensive and would probably not be cost-effective

unless particle size was very small (sawdust size)

8) note that saprophytic microbial activity produces CO2 - the build-up of which must be exchanged with O2 as part of the composting process - and in this example - since moisture of the feedstock is no longer an issue - the aerated static pile method would be my choice to accomplish necessary gas exchange to continue decomposition at the fastest possible rate,

But both positive and negative air flow would be necessary to control high heat produced by thermophilic activity - which if allowed to become excessive - will severely damage mesophilic populations - requiring a longer curing time to restore full microbial community maturity

The above list simply outlines the possible general activities that might be considered in treating a high-carbon feedstock to increase microbial decomposition over time. How each step in the outline would affect cost-effectiveness - of producing the same (or higher quality) end product over time - will depend on numerous factors.

Nitrogenous feedstocks are handled differently.

So to your question relative to cost-effectiveness - the answer is: DEPENDS.

If you provide a set of specifics on which a cost/result (over time) analysis can be made, then I could address the issue of cost-effectiveness relative to the present process being used. But this is not the forum to do that - so please respond by email if you would like to pursue your question in more specific terms.

It depends on the time and the habitat where microbes living. Initially, low C/N ratio material is easily decomposed and can prime the rapid growth of general microbes, while during later decomposition process when microbes reach higher density, the decomposers can find other N sources from the environment (eg., or may synergistically interact with N-fixing bacteria).

Thanks Robert, you did justice to my question.

To answer in one sentence, YES it depends on C:N ratio. Wider the ratio slower the decomposition rate and vice-versa.

I prefer the answer: "Depends" (upon multiple factors - as noted).

However, the answer "Yes - within C:N range limits (not too high or low) AND following first priorities - as noted" is also substantially correct.

First priority is that moisture must be present (with DO content) needed to ascertain C:N and provide microbes with an environment conducive to decomposition activity).

Second, the issue of particle (surface area) size that can change C:N nutrient availability to the microbial level.

Third, the entire question of C:N nutrient availability is relative to the density and diversity of the viable (not dormant) existing (and/or inoculated) microbial community available to act upon (mainly the surface area) of compost feedstock material (without the full synergistic community, decomposition will not (if sterile/contaminated) occur even with a 'perfect' C:N ratio).

In addition, existing C:N is dynamic and can be altered (on-the-fly) by adding appropriate microbially-available carbon and nitrogen (in soluble form) to alter immediately-available C:N nutrients (to the microbial community) within the range desired. Meaning that decomposition rate is not totally dependent upon (nor limited to) the existing C:N ratio of a given feedstock (or mixture thereof).

C:N can be a good predictor of nitrogen mineralization and decomposition rates, but the quality of the carbon matters. Lignin is slow to decompose, cellulose is less slow, simple sugars, even less so. I've seen lignin:N used as a better predictor, but lignin is not as easily measured as total carbon. Higher C:N (or better yet, higher lignin:N) slows decomposition, all other factors (e.g., decomposer populations, water content, temperature, pH, etc.) being equal,

Peter,

"...all other factors (e.g., decomposer populations, water content, temperature, pH, etc.)" are NEVER equal...

But do agree with you that : "the quality of carbon matters."

For high-cellulosic/lignin composting feedstocks, pre-treatment with soluble nitrogen. to 'kick start"' the microbial decomposition process (by balancing the C:N ratio) should be considered.

recent evidence in the literature is challenging the previously widely held idea that molecular composition (including C:N, lignin:N ratios and similar metrics) alone can strongly regulate decomposition of organic matter. The dependence of decay rate on C:N ratio is likely in the short-term and co-evolves with the physical conditions in the environment decomposition is taking place. Evidence is now mounting that, in the long term, physico-chemical and biological influences that OM encounters in the environment play important more important roles in reducing its likelihood for decomposition and other loss processes (including leaching and erosion), compared to its chemical compositions.

for more discussion on this see Schmidt et al 2011, Nature.

Looking at your question from the agricultural point of view, I see two competing needs for N. One is the need for soil microbes to feed themselves and two, the need for the crop, for example for nitrogen fixation in a legume crop or legume-cereal inter cropping system. Increasing nitrogen availability in the soil reduces competition for the this nutrient during the process of residue decomposition, which could mean that decomposition would proceed as determined by soil temperature without depriving the crop of the nitrogen needs at any particular stage of growth.

When C:N ratio is at equilibrium, the rate of decomposition of organic matter is determined by soil temperature and nature of the plant residues and hence, N availability to the crop. This latter N becomes largely available from the decomposed organic matter. Thus, high C:N ratio may influence the rate of organic matter decomposition but caution should be observed when using straw residues as mulch for dual purpose of soil enrichment and protection against high air temperature and torrential rain storms. One should ensure availability of a starter-N to stimulate microbial activity for future synthesis of N from the residues. From this discussion it appears that high C:N ratio would be good for organic matter decomposition in the soil through enhancement of microbial activity. The rate of the process will eventually depend on the nature of the residues, soil temperature and soil water. I hope my contribution will stimulate further discussions on this important topic.

Got your question later, but I hope my explanation may help. A lot has been told above, from forest ecosystems point of view: I think that C/N ratio is just expression/index of complex conditions (e.g., climate) affecting organic C and organic/inorganic N. It can not affect a decomposition rate itself. It traditionally serves as a rate index. In forest soils of the North Hemisphere, for example, there are humus layers (litter/duff etc.) on a mineral soil. The harsher climate the thicker humus (boreal forests, high mountain conifer forests) because of low temperatures, microbial activity etc. and thus low decomposition and digest of OM. Contrary, Mediterranean warm oak forests have almost no litter because high decomposition rate of oak leaves in warm convenient climate.

So, you might ask better: what stands behind fast/low decomposition of OM and how C:N ratio reflects that?

Tony

OM decomposition is almost entirely microbial in nature (pun intended). Both the degree and rate of microbial decomposition of OM is dependent upon diversity of and density of the microbial community that 'does the work', which is primarily factored by the environmental conditions within which the microbial community depends - to establish a consistent reproductive rate over time.

Very basically, carbon (for energy) and Nitrogen (amino-protein to build cells) usually expressed as C:N, along with O2 in water are required for aerobic microbial reproduction - requiring a sufficient supply of of all three basic elements (along with other adjunct factors such as mineral availability) to act efficiently on OM,

So the answer to the posted question is YES - BUT DEPENDS on the extent that other primary factors are also present (since C:N is not the only primary factor).

Robert, thanks for the great complement.

T

Very interesting question!

My answer is in conformity with Robert Moore. Because organic matter (OM) decomposition is a complex mechanism, it is govern and regulated by microorganisms. Conversion of organically bounded material (carbon, Nirogen and Phosphorus) into simpler form is known as mineralization. Normally, microbes prefer to decompose nitrogen and phosphorus rich litter instead of rich carbon. Carbon is however an essential need for getting energy but microbes prefer building element like N and P.

Based on my experience, decomposition rate would be faster of those litter will contain high quality and quantity of of N and P instead of Carbon. But C:N ration will not be whole sole reason, there would be some other determinant factors which may govern rate and rapidity of organic matter decomposition.

Conclusion: Microbes prefer to decompose very fast litter which contain high quality and quantity of N and P.

Yes organic matter decomposition depends on C:N ratio. If the C:N ratio is too high in case of sawdust then decomposition is low and if it is low in case of peastraw then decomposition is high. It is due to more water soluble carbon avaiable for microbes.

@ Priti Roychand,

C:N ration an important parameter to know basically carbon and nitrogen concentration present in the litter. I am agree with you that C:N ratio play good role in the decomposition but widening of the C:N ratio also indicates the quality of litter. For example, a litter has 0.1 percent nitrogen and 48.0 percent carbon then C:N ratio would be 480, at the same place, another litter source collected from a leguminous plant shows 48.0 percent carbon but 4.5 percent nitrogen, here C:N ratio would be 10. Now decomposition rate will be faster in the latter one and slower would be in the first litter type. It is because of C:N ratio.

However, I can say with evidence, for decomposition except C;N other factors are also responsible for faster decomposition.

In some case cases, especially from desert environment, C:N ratio of available litter in the desert ecosystem exhibited a favourable C:N ratio which may favour but oppositely it showed slow decomposition. It is because of other factors which are responsible such as moisture and kind of saprophytes available in the soil environment there.

Yes it is very true: It is due to more water soluble carbon available for microbes. I quote your last sentence as a conclusion.

Many speak of C:N as a static issue - but it is not. C:N is a DYNAMIC component of the decomposition process - constantly changing naturally, due to changing environmental factors. But the point is: C:N is a component that is easily adjusted "on the fly". Consideration of the C:N ratio in the field is pure 'guesswork' - only 'definable' in a laboratory - hence a value-judgement issue. Both nitrogen (in the form of amino acid proteins) and carbon (usually in the form of simple sugars) used by the microbial community to reproduce, can be inoculated in liquid form to alter the C:N to more favorable microbial reproductive conditions - hence faster decomposition rate. Also adding additional LIVE aerobic microbes to feedstocks via liquid solution - to increase saprophytic activity - is also quite simple. Therefore compostable material which might take 6-9+ MONTHS to process through the stable/finished/mature stages in a given environment (capable of beginning efficient nutrient cycling to plants and initiating effective disease/pest control) can easily be significantly time-decreased by altering the INTERNAL composting environment. Composting is a man-contrived process that simply speeds-up- the natural biological processes of nature.. It is not unusual for an experienced composter - using scientific methods - to produce high-quality MATURE compost - from RAW materials - in 8-12 weeks - depending on how well feedstocks are processed and the decomposition rate controlled.

ya its sure as C:N ratio determine mineralisation.

if C:N ratio >30 immobilisation of nutrient

Yes, Dr. Amanullah saheb, I am agree with you. It is because of higher concentration of N and low concentration of carbon attracts more saprotrophs. Faster decomposition of those type of litter which contain significant amount of N concentration.

C/N is an index commonly used in soil science and other related fields to indicate the "rate" of decomposition of organic matter. All things being "equal", the organic matter in question should be similar (source and conditions under which they are found). Organic matter with a high C/N ratio will readily decompose than a similar material with low C/N ratio.

Let's pit facts straight. High C/N ratio means high levels of carbon and low levels of nitrogen and vice versa. Organic material with high C/N ratio means that it has low nitrogen. Decomposers, therefore, will scavenge for N from other sources for their own needs thus delaying decomposition of the organic matter.

C:N rato is the most important for microbial decomposition of organic matter in edaphic or aquatic environment. Unless and untill optimum C:N ratio (based on stoichiometry of biomass) is not provided, proper decomposition of organic matter would not occur. The ideal C:N raito for composting is generally around 30:1. Higher ratios mean that there is not sufficient nitrogen for optimum growth of microbial population so decomposition will be slow. In this case you have to fortify nitrogen source through nitrogen fertilizer. At lower ratios, carbon is in short supply (whole carbon is decomposed) and nitrogen is in excess and will be lost as ammonia gas, causing undesirable odours. In this case it is necessary to incerease organic matter conctent in the compost.

Try that relationship:

C------NITROGEN REDUCTION FACTOR ON EXOGENOUSLY ADDED OM (RESIDUES) DECAY (RTF(I)>0).

C ------------------------------------------------------

C---------RTF(I) IS THE N LIMITING REDUCTION FACTOR FOR EACH RESIDUE (I)

C---------COMPUTED AT EVERY TIME STEP

C---------CNRATE = RATE OF C OUTPUT FROM EACH RESIDUE

C---------DIVIDED BY (NH4+NO3)-N AVAILABLE

C---------PLUS N OUTFLOW FROM RESIDUE (I) PER TIME-STEP (REFER: '*DELTA').

C

DO 31 I=42,45

XNCN=CONC(18)+CONC(21)+((RED*CF(I)*CONC(I)*DELTA)/CN(I))

IF(XNCN.LE.0.) XNCN=.001

CNRATE=(RED*CF(I)*CONC(I)*DELTA)/XNCN

IF(CNRATE.LE.10.) RTF(I)=1.0

IF(CNRATE.GT.10..AND.CNRATE.LE.20.)

1RTF(I)=(1.0-0.70)*((CNRATE-20.0)/(10.0-20.0))+0.70

IF(CNRATE.GT.20..AND.CNRATE.LE.50.)

1RTF(I)=(0.70-0.40)*((CNRATE-50.0)/(20.0-50.0))+0.40

IF(CNRATE.GT.50..AND.CNRATE.LT.80.)

1RTF(I)=(0.40-0.25)*((CNRATE-80.)/(50.0-80.))+0.25

IF(CNRATE.GT.80.)

1RTF(I)=(0.25-0.20)*((CNRATE-120.)/(80.-120.))+0.20

IF(RTF(I).LT.0.2) RTF(I)=0.2

31 CONTINUE

conc(i): concentration of decaying exogenously added OM (i)

of cn ratio cn(i)

conc(18): concentration of (NH4+)-N

conc(21): concentration of (NO3-)-N

delta: time step

cf(i): specific decay rate of residue

(first order decay rate, refer cf(i)*conc(i)

red: gener

Let me know it in simple way

RTF(i)

1.0 | *

|

|

0.7 | *

|

|

0.4 | *

| *

0.2 | * *

|

0.0 |_____________________________

10 20 50 80 120

CNRATE

rate(i)=rtf(i)*cf(i)*conc(I)

rate(i): actual decay rate

of exogenously added OM (residue)

to soil

cf(i): specific decay rate

at optimum conditions of decay

conc(i): residue concentration

rtf(i) reduction factor on

the optimum decay rate

computed at each time step

of the numerical integration

cnrate: is not the CN ratio of the residue.

it is the ratio of

the optimum C decayed from residue

divided by inorganic N available:

nitrate-N plus ammonium-N

plus optimum N decayed from residue (if any)

at each time step.

Yes but the main factor is not the C/N ratio but first the nature of the fresh C/N ratio that will influence the soil biological activities (biomass and sensus stricto activity) and second the intensity of the Rhizosphere Priming Effect (RPE) on the older organic matter, and/or the priming effect issued from the residues that affect the older organic matter on bare soil (during the fallow period or covered soils if the study concerns agriculture soils).

yes and these factors have to be included in any quantitative model of C and N dynamics in soil. There is not one main factor but the whole has to be considered and integrated. Refer for example Geoderma 81 (1997) 153-225.

-Yes definitely organic matter decomposition is dependent on C:N ratio.

- the C:N ratio of 10:1 to 12:1 is required for microbial biomass decomposition. then a well decomposed organic matter has a C:N ratio of 12:1 to 20:1. more than that is not suitable.

Effect of C:N ratio

First of all we have to see the type of material from which organic matter prepared.

For example if it prepared from leguminous material the C:N ratio is narrow (10:1 to 25:1) because the presence of higher nitrogenous material in that than carbon inturn helpful in microbial biomass multiplication. from this the rate of decomposition will be faster and availability of nutrients to the plants (i.e. mineralization rate) will be more and vigorous. If you apply organic matter having wider C:N raito (cereals and coconut fronts) leads to "nitrogen depression" (Nitrogen locking in microbial body) inturn leads temporary unavailability of nitrogen in plants.

-Then higher and lower not the matter. it should be mentioned as wider and narrow C:N ratio. for better availability of nutrients narrow C:N ratio is required than wider .

Kudos and plaudits to my Colleagues who commiserate and comment on this subject.

As a soil/plant microbiologist specializing in decomposition of compostable feedstocks, allow me to interject a quandary into this discussion.

The majority of you speak in terms of C:N ratio in relation to "microbiology" as if that microscopic community was "one being" - which it IS NOT.

While the beneficial aerobic microbial community acts in a SYNERGISTIC manner, this microbiological community of which you speak in such 'generic' terms is actually composed of a MULTIPLICITY of different bacterial, fungal (and protozoan) species, EACH of which acts on 'organic material' in DIFFERENT WAYS (specifically via production of [and utility of] the ENZYMES they produce, which actually perform the WORK of decomposition - to solubilize/transform that MATERIAL into MATTER and eventually into HUMUS - the amphorous ultimate END to the decomposition process [as far as microbiology can take it - one of the most complex molecules known to science]. That being said, science still knows only very little of the microbial knowledge it needs to learn.

So while some of you say that "this or that" C:N ratio pertains to optimization of decomposition rate - you should understand that no matter what the C:N ratio of ANY given feedstock material 'BALANCE' is - there are certain 'classes' of microscopic biota that are capable of acting on WHATEVER C:N RATIO EXISTS [yes, the generally-accepted 40:1 to 20:1 ratio 'range' is optimal - as long as the "BALANCE" of air (in the form of FREE oxygen) and H20 exists - without which, NO decomposition will take place (since such aerobic microbiota will be DORMANT - no matter what the existing C:N composite ratio is.

So while C:N ratio is certainly important to decomposition rate, it is NOT the primary necessity that determines the decomposition rate of organic (carbon-based) material - but ranks only 4TH in necessity.

OK - given that the 'proper' O2 / H20 conditions DO exist, CARBON is needed to provide energy to microbes and NITROGEN (in the form of amino acids in protein form is needed - along with some additional phosphorous and potassium) to build cells (microbial reproduction capacity) - but understand that such balance [whatever it is - is dependent upon adequate O2/H20 availability) and CAN be utilized by certain species of microbes.

And yes, the percent of CO2 existing within the mix (which both chemistry and microbes create) is important - an over-abundance of which - will drive ALL aerobic microbes into [inactive] dormancy).

Microbes (et al - synergistically speaking) actually CHANGE the MOLECULAR STRUCTURE of organic (and inorganic) material depending on the physics/chemistry makeup (yes, chemical reactions also occur based on the ionic characteristics of the mix too (in the presence of O2 & H2O).

I hope this input - intended to clarify - does not confuse you...

So as stated in my previous comments in this thread - the true answer to this C:N question is:

DEPENDS (on a multiplicity of conditions - ONE of which is the "makeup" of the existing microbial community). If artificially (by inoculation of Liquid Microbial Concentrate [meaning that the beneficial bacterial OR the fungal community population of the 'mix' is increased] - the existing C:N ratio will be utilized in different proportion.

Only in the presence of O2 & H2O does C:N of a given compost C:N determine the 'makeup' of the total active microbial community [and therefore its synergy] that is available to 'work on' the organic matter.

Do you desire to develop a high-bacterial finished compost? Or high-fungal? Or balanced 1:1 Bacterial-to-Fungal [B:F] ratio (i.e., is your compost intended to nourish 1) grasses, or 2) trees or 3) fruits~vegetables~ornamentals?

Depending on intended result, so alter the C:N ratio to create the desired microbial chemical environment and resultant population. THAT IS THE FUNCTION OF C:N (in the presence of appropriate O2/H2O content).

And one last note: PARTICLE SIZE is the PRIMARY determining factor of any given compost feedstock decomposition rate (THE main microbial population determinate - based on surface area available - a food source availability issue).

The SoilGuy

Note that for composted materials, the C:N ratio can be interpreted differently, since stabilized compost usually have a lower C:N ratio compared to fresh plant materials, but are more stable once applied in soil. This is due to the fact that during composting, the N and C are transformed into more stable forms...

Sujit, of course C/N ratio is very important for organic matter decomposition. Besides lower the C/N ratio better it is for decomposition process. However there are many other factors also which govern the process but C/N ratio is of prime importance.

C/N ratios might control decomposition of organic matter.

However, polyamide resin (called nyron) is not easily decomposed in a soil.

please think about quality of the organic matter.

It is important to note that the C / N ratio is only an indicator of the rate of mineralization of organic matter (OM). Sometimes are not considering is the quality of the material organic , example one ton of organic material that is really far from easily degradable ie has a C / N ratio 10:1. So any other indicators that could be taken would have to consider the quality of the MO.

Materials with lower C/N ratio would be much faster and easier to be decomposed by the decomposers.

In Bio-degradation the Organic carbon decreases and the matured compost will show higher nitrogen as compared to the original material composted.

Hence the decrease in organic carbon along with C/N ration has to be interpreted together.

To add an aquatic ecosystem perspective. I enclose a classic paper for your consideration ENRIQUEZ, S., DUARTE, C. M. & SANDJENSEN, K. 1993. PATTERNS IN DECOMPOSITION RATES AMONG PHOTOSYNTHETIC ORGANISMS - THE IMPORTANCE OF DETRITUS C-N-P CONTENT. Oecologia, 94, 457-471.

To summarise, they found a series of empirical relationships across different plant communities with different median C?N due to structure differences (e,g. phytoplankton are protein bags, seagrass are lignocellulose bags). However, it should be noted that the relationships appear to breakdown within the same groups.

I also reference work on Stoichiometry theory by Sterner and Elser (many references). One basis is that the consumers productivity (grazer or decomposer) is always by its lower C/N or other limiting nutrient and homeostasis than its plant source (variable and higher C/N).

That constraint in the supply of nitrogen to break down organic carbon, however, i n some cases maybe circumvented by viral lysis of bacterial or archeal populations. Ths has hypothesis been proposed and tested for the deep sea sediments where 90% 0f the organic matter is decomposed this way cf coastal sediments maybe around 20 % with a lower viral load.

Hope this helps and doesn't confuse

Though C N ratio is important , it is not the sole parameter, the nature and property of the material to be decomposed definitely has a profound effect on the rate of decomposition. Tannin and phenol rich material may take a tad longer to decompose than cellulose rich material , though both may have identical C N ratios.