https://dl.sciencesocieties.org/story/2015/jun/mon/anthropogenic-and-climatic-controls-on-soil-organic-carbon-stocks-in-india

Link for Organic carbon source

Carbon in soil is present ideally in two forms. These are, soil organic carbon (SOC) and soil inorganic carbon (SIC).

When you talk about manure and CN ratio, we consider only the organic form of carbon. The manure to be applied in soil for enhancing soil quality to effect better crop production has to be quality compost. If we do not follow the recommendation of addition of well decomposed manure in soil, then the soil may go into nitrate depression period (please see Buckman and Brady’s book on soils) which will affect the crop production. While working in carbon modeling (Roth C), the carbon content of FYM added in different treatments is required. While working on models, I happened to cross check the percentage carbon present in different types of manures used in different treatments. As against 33.3% carbon used for FYM in Roth C model, I found many of our manures contain low carbon content.

Since stage of decomposition of manure as well as the amounts are important. It should, therefore, be noted that for all Long Term Fertilizers Experimental Trials, the scientists may report the percentage of carbon present in the manure they are applying for different treatments. This is also important that nitrogen supplied to the plant from manure is through the manures (other than inorganic). Knowledge of the ratio of carbon : nitrogen, therefore, is an important parameter.

Regarding effect of manure on C : N ratio and carbon content in soils, we have carried out some research work on different pools of organic form of carbon. We have found that active pool of carbon in the soils of the Indo-Gangetic Plains (IGP) is relatively more than that in the soils of the black soil region (BSR). This has been explained as the effect of very high seasonal temperature in the central, western and peninsular part of the country where normally the black soils are found. Moreover, these areas also receive relatively low rainfall as compared to the IGP. This suggests that perhaps the manure application, normally followed as a single dose annually, may be split into two in the BSR to help the rabi crops under irrigation.

I do not know, if I could answer your query. You may find these thoughts in some of our publications available in Research gate.

Regards,

                                                                                   Tapas Bhattacharyya

Dr.Singh,good question but not easy to answer.Indian soils rarely contain more than 1.5% organic carbon.Foot-hill soils(Hapludoll) of Pantnagar may have organic carbon of 1.5-1.6 %.Vertisols may contain organic carbon in the range of 0.4 to 1.0%.Fine- textured and irrigated soils especially under rice cultivation may contain organic carbon in the range of  0.5-0.8%.Alluvial soils may contain organic carbon in the range 0.2-0.4% even under irrigated conditions.Red soils may also contain similar level of organic carbon.Soil texture,irrigation/assured rainfall ,temperature and regular return of organic residues ,roots,manures/composts decide th level of organic matter in soil.High N containing and fast decomposing organic materials(legume straws/residues and well decomposed manures/composts) may not leave more   amount of stable carbon pool to remain in soil and then add to total passive pool of carbon.Wide or high C:N ratio materials may decompose slowly and may leave more stable carbon in soil.So they may increase the passive C pool in soil.There are differences in manures varying in C:N ratios and their total N and constituent N pools.If one compares cattle manure,chicken manure and pig manure,on average,13%,21% and 19% of their organic  N get mineralized in161 days.Amino acid and ammoniacal N in manure contributed(96-97%) to mineralization.(reference provided at the end ).How far the stable pool of  carbon  in the organic material added contributes to stable pool of carbon in soil may differ in soils.As per carbon saturation theory,the C unsaturated soils may show more change the carbon status(with organic matter addition) compared to carbon saturated soils.If the added organic material is not increasing soil carbon means ,it will be more suceptible to decomposition.Also,continuous addition of organic manures may increase the more labile carbon and its subsequent mineralization.

Nitrogen mineralization from animal manure and its relationto organic N fractions.By LI Ling-ling and LI Shu-tian Journal of Integrative Agriculture Advance online  Publication2014.Doi:10.1016/S2095-3119(14)60769-3

file:///C:/Users/matrix/Downloads/9415.pdf

Dear Gaurav Singh,

Possibly they are related but *only within a narrow range of soil clay+silt contents*. The overall soil C build-up is governed by soil clay+silt content.

Soil carbon saturation capacity is positively related to its clay+silt content.

I would recommend you look for relevant papers on these key words.

The C:N ratio of manure applied to the soil really relates to the rate at which the manure will decompose and the N will become available for plant use.

Soils generally have some relatively stable background C:N ratio that is related to the soil parent material, climate, vegetation being grown on the soils, soil management and fertilization.  Addition of manure with a different C:N ratio m will cause a small shift (depending on the quantity of manure applied and The C:N ratio of the manure) that is a short term  shift (a few weeks to a few months).  As the soil biological activity results in decomposition of the manure, the soil C:N ratio will tend to shift back to  its original, stable C:N ratio.  However, with long-term, heavy manure applications the baseline soil ratio can shift on a more permenant basis.

The C:N ratio of manure will determine the  rate of N being mineralized from the the manure material.  Generally, manures with C:N of 30+.  This is in line with most classic textbook information.

Essentially, soil C:N ratios are the product of the quality of organic inputs, soil chemical characteristics, management, climate and production levels (offtake of nutrients).

You mix QUANTITY & QUALITY. Please do not confuse. SOC & C/N are two independent variables. Please review, as example, my papers dealing with SOM.

 Dr.Cihacek,I compliment good and clear reply

Even if the C/N ratio < 20, there is also chance of immobilization of N as N mineralisation depends on quality of manures i.e. lignin, polyphenols and other relatively or moderately susceptible to decomposition compunds like cellulose and hemi-cellulose. Please refer to Probert et al., 2005 article in Soil Biology and biochemistry.

Dr.Mohanty you may give full details  of the paper you mentioned and also your own publication/publications on the same aspect.

Surely there is ANY correlation between soil organic carbon and C/N ration of the manure applied in the soil. 

But the question is too general to be answered that it is not biased. It would be easyer to help, if you add a good description of the problem you want to solve. J HUMER

A addtional problem here is

that C org ist even a part of C/N, and therfore a half biased vicious circle and self dependend autocorrelation! J HUMER