This is the point , we have been debating quite aggressively , what to do and how to do with current agricultural practices in lieu of changing climate , knowing the fact that soil carbon is bound to play a pivotal role to moderate the impact of climate change.  

Foremost of them is the crop diversification , intervention of cropping sequence involving annuals as well as perennials , use of rhizocompetent multiple inoculation  strategy ( for maintaining as wider  soil microbial diversity as possible) , floor management using variety of cover crops, and most important of all is the revision of fertilization and  irrigation scheduling , besides revisiting the accuracy of RDF. 

From our observation we have found 2-3 times faster C mineralization at 45oC compared to 28oC air temperature. How to stop such event?

Dear Dr. Biswas,

I wish to emphasize on the vital role of  land use and land cover in conservation of carbon under changing climate.  Rampant conversion of native vegetation to cropland goes on everywhere in the world, although we are not sure whether it is the cause or the effect of changing climate. 

(1) After emissions from the fossil fuel combustion, carbon emissions resulting from changes in land use and land cover are the second largest source of human-caused carbon emissions to the atmosphere.

(2) So far most policies aimed at reducing CO2 emissions have focused on carbon stored in plants, despite the fact that more carbon is stored in soils than in plants. The majority of carbon stored in the soil is the result of millennia of decomposition of organic matter. Estimates of global soil carbon stocks are uncertain, and carbon emissions from land use and land cover change remain the least understood component of the global carbon cycle.

(3) Policies designed to reduce emissions of carbon have not fully considered the effects of land use and land cover change on soil organic carbon stocks and their emissions, despite significant losses of soil carbon. In some cases, for example, up to 50 per cent of soil organic carbon is lost when native vegetation is converted to cropland.

Therefore I wish to focus on the ''land use and land cover'' issue in conservation of carbon.

Dr Kundu,

Thanks for your response. In Bangladesh, for example, there is no more virgin land to convert for crop culture. In some places already degraded, but we need more food to feed our people. We have also to conserve soil carbon- how? We know, one meter soil can contain some peta gram carbon, the question is how to increase soil carbon when it is already degraded and we have no time to allow its fertility/productivity?

Dr Kundu , very good points. Infact , while moderating the climate change induced carbon emissions, our major emphasis stressed on the use of crops/cropping sequence capable of sequestering carbon in annual or perennial framework depending upon the  annual or perennial crops, land cover could be one viable option . Likewsie , perennial crops , especially fruit crops like citrus , apple  have the capacity  to sequester as much as 30-50 tons carbon /ha/year. On the other hand , while debating on the issue of  storing carbon into the soil (  needless to say, soil better equipped to store carbon than plant) , especially in tropical/subtropical climates , even arid climate , the elevated carbon concentration in soil realised through Long Term Fertilizer Trials could never be deposited into the non-labile fraction of soil carbon , despite all out efforts . In this background  , what should be our onward way forward approach ..? Do you feel changes in current land use pattern could be one of them..since simple land cover will not fetch us addition foods for so constantly growing population . Dr Biswas has some merit  in saying so....

Thanks, Dr. Srivastava, for your pointed response.

While searching various ways for conserving carbon, I really didn't consider the cases of any individual country or region. The point I have raised is applicable at the global level. Take the case of Bhutan. How that small country has successfully maintained their soil carbon level (in fact carbon surplus) and has become a model for the globe. Had Bhutan opted for deforestation to go for some more lucrative ventures for short-term economic prosperity of their country, they would not have maintained their climate unchanged. As I have mentioned, carbon loss from soil to atmosphere is second largest contributor to global warming, and we can't afford to ignore this issue while looking for the ways of conserving carbon. UNEP is now vigorously campaigning for absorbing atmospheric carbon by fast-growing timber plantations and recycling that back to the soil, because soil is (perhaps) the largest sink for carbon. My point is against the clearing of land and still hoping for conservation of carbon! You may have several other ways of conserving carbon, but their contribution to mitigate global warming (climate change) can not be as great as that of conservation of soil carbon.

Hope now I have communicated my point a bit more clearly. 

nice question, Dr Biswas, we can enrich carbon content through adoption of suitable agronomic and inputs management, which may benefit to the immediate crops but in cases of tropical and sub-tropical regions where the temperatures are higher and in CC situations it may further increase then as you pointed out the carbon degradation will be fast and we may not be able to have resultant increased C content over a longer term basis. However these practices may give immediate benefits to the ongoing crops in terms of growth and yield. 

carbon sequestration in the top soil layers under tropical and sub-tropical regions is a bit concern, where as capture of carbon in the deeper layers, beyond the root zone is possible measure for reduced emissions

Take the examples of sandy and loamy sand soils of India, the resultant increase in carbon content in root zone layers is almost negligible with intensive cultivation as well with residue incorporation, although we get benefits in growth and yield of ongoing crops

DST India is funding network project on carbon sequestration for the last couple of decades, and one can go into the reports of possible capture processes, through inorganic/organic means, and you can go through these reports on the website.

regards

Nice response Dr Kundu , i appreciate your comprehensive answer with a clear mind set. No doubt , this discussion crosses any geographical boundary , and it is not good also to have discussion on a  regional basis. Dr Kundu , i am more concerned with the tropical countries where  year-round high temperature with a wider diurnal variation coupled with high RH , precipitation are common features . Under such conditions,  conserving carbon in soil  for carbon surplus condition is more challenging  than temperate climate soils, besides just look at the ecological balance in terms of oxygen available per capita through the better ratio forest area vis-a-vis arable land area and  population density . Many of our problems are population demand- induced including the well known environmentally abusive practices of shifting cultivation , so prevalent in northeastern India.  How does agriculture  survive , simple carbon accredition through forested area , but with time, deforestation started , and now , it is a different scenario plus extra burden of negative consequences of shifting cultivation . your point is well taken , it has to be two pronged strategy , looking at the carbon credit earning land uses  and expanding the forested area , with a vigil eye on cutting the menacing   rate of unwarranted soil  erosion , Dr Redddy has rightly pointed out...

Dear Dr Srivastava, thanks for your specific response to my earlier reply.

Now I present some ways of conserving carbon exclusively for humid tropical regions. For humid tropical regions like eastern India and Bangladesh, just by expanding area under Jute cultivation we can absorb large quantity of carbon dioxide from atmosphere and return to the soil. In fact, in 120 days period, jute crop grown in one hectare area can absorb 15 ton of carbon dioxide from air which can be returned to the soil. The capacity of Jute plant to tap atmospheric carbon dioxide is more than other fast growing perennial forest trees like eucalyptus and pines (these trees can fix about 11 tons of carbon dioxide per hectare area in 120 days period). This is one example of simple ways for conservation of carbon in soils in humid tropical regions.

I hope all my RG friends interested in this subject find this information interesting and useful.

Thanking Dr Kundu , let me add an abstract of very good exhaustive study for the benefit of all   our RG friends..hope , they like the content ...

F. DOU,A. L. WRIGHT,R. S. MYLAVARAPU,JIANG Xian-Jun,J. E. MATOCHA. 2016. Soil enzyme activities and organic matter composition affected by 26 years of continuous cropping (Title in Chinese: 26年连作影响下土壤酶活性和有机质组成). PEDOSPHERE. 26(5): 618--625. View Full Text at: http://www.sciencedirect.com/science/article/pii/S1002016015600704

Abstract: The study was to determine the long-term effects of subtropical monoculture and rotational cropping systems and fertilization on soil enzyme activities and soil C, N, and P levels. Cropping systems included continuous sorghum (Sorghum bicolor L.), cotton (Gossypium hirsutum L.), corn (Zea mays L.), and cotton/sorghum rotations after 26 years of treatment imposition. Soil under continuous sorghum and continuous corn had 15% and 11%, respectively, greater C concentrations than soil under continuous cotton. Organic C was 10% higher at 0--7.5 cm than at 7.5--15 cm. Total N followed similar trends with soil depth as organic C. Continuous sorghum had 19% higher total N than other crop species and rotations. With fertilization, continuous cotton had the highest total P at 0--7.5 cm and sorghum had the highest at 7.5--15 cm. Soil total P was 14% higher at 0--7.5 than at 7.5--15 cm, and fertilization increased 15% total P compared to unfertilized soil. Arylsulfatase, alkaline phosphatase, and β-d-glucosidase activity were the highest for sorghum and the lowest for cotton. Rotation increased enzyme activities compared to continuous cotton but not for continuous sorghum. Of all crop species and rotations, continuous cotton generally showed the lowest levels of organic matter and enzyme activities aft 26 years. Fertilization significantly increased the yields for all cropping systems, but rotation had no significant effect on either sorghum or cotton lint yield compared to each crop grown in monoculture. Long-term cropping did not increase soil organic matter levels beyond short-term gains, indicating the difficulty in promoting C sequestration in subtropical soils.

Just imagine , in 26 years time , there was only 11-15% higher carbon  realised compared to baseline concentration ...

Dr. Srivastava,

I present the data of long term fertiliser experiment (LTFE) involving jute-rice-wheat cropping system which started at Barrackpore, North 24 Pargana district, West Bengal in 1971. Presently I am the Principal Investigator of the project at this centre. After 44 years of cropping, organic carbon content in the gangetic alluvial soil (inceptisol) has increased from 0.56 to 0.87%. It means approximately 50% increase in 44 years. This indicated the positive influence of jute cultivation on conservation of carbon.

I share this information for the benefits of all my RG friends.

Very good feedback  Dr Kundu , appreciate it . These results also display the fact  about the strong possibility of conserving carbon into non-labile pool to inluence nutrient supply through  labile carbon pool of the soil . 

Abhishek, 

Thanks for the attachments. We have seen less C emission depending on the choice of cropping patterns. Inclusion of non-rice crop in rice-rice patterns showed less global warming potential.

Identification of  agroecological beased suitable land uses , introduction of legumes in the cropping sequence and crop management policy need to be reoriented  or revisited periodically . What would be the time lapse for such assessment , needs to be worked out . How entomologists and pathologists keep evaluating newer molecules to provide as many alternative options for their use , simply to avoid development of any possible resistance , besides they could be inactive over a period of time depending upon the peak egg laying of the pests ( Reverifying the life table of pests  in the lightclimate change ..?)or pathogenicity of the pathogens...sorry bit out of context ..but needed to put my point... 

The transformation of manure and other organic waste previous composting is a viable strategy to rise labil C usefull for microbiological activity, so in compesation C non labil is preserved but is necesary the aggregation for physical protection of C. The use of pectins from succulants plants and Actinomycetes muscilages can contribute positively on micro-aggregation.

One can conserve carbon by huge plantation on earth.