Dear Dr.Phogat - It is an important issue. I do not have any direct answer but I can request you to go through some of good Indian long-term experimental work on this aspect. Some references are cited below for your perusal. Please ignore if you have already referred these.
Majumder B, Mandal B, Bandyopadhyay PK, Gangopadhyay A, Mani PK, Kundu AL, Mazumdar D (2008) Organic amendments influence soil organic carbon pools and crop productivity in a nineteen-year-old rice–wheat agro-ecosystem. Soil Sci Soc Am J 72:775–785
Majumder B, Mandal B, Bandyopadhyay PK (2008) Soil organic carbon pools and productivity in relation to nutrient management in a 20-year-old rice-berseem agroecosystem. Biol Fertil Soils 44:451–461
Mandal B, Majumder B, Bandyopadhyay B, Hazra GC, Gangopadhyay A, Samantaroy RN, Misra AK, Chowdhuri J, Saha MN, Kundu S (2007) The potential of cropping systems and soil amendments for carbon sequestration in soils under long-term experiments in subtropical India. Global Change Biol 13:357–369
Majumder B, Mandal B, Bandyopadhyay PK, Chaudhury J (2007) Soil organic pools and productivity relationships for a 34 year old rice–wheat–jute agroecosystem under different fertilizer treatments. Plant Soil 297:53–67
Six J, Conant RT, Paul EA (2002) Stabilization mechanisms of soil organic matter implications for C-saturation of soils. Plant Soil 241:155–176
Mandal B, Majumder B, Adhya TK, Bandyopadhyay PK, Gangopadhyay A, Sarkar D, Kundu MC, Gupta Choudhury S, Hazra GC, Kundu S, Samantaray RN, Misra AK (2008) Potential of double-cropped rice ecology to conserve organic carbon under subtropical climate. Global Change Biol 14:1–13
Manna MC, Swarup A, Wanjari RH, Singh YV, Ghosh PK, Singh KN, Tripathi AK, Saha MN (2006) Soil organic matter in a West Bengal inceptisol after 30 years of multiple cropping and fertilization. Soil Sci Soc Am J 70:121–129
Carbons sequestration is basically the difference of Primary Plant Production as a function of Photosynthesis minus the Loss of this Primary Productivity through Respiration much of this is related to decay and consumption by animals and microbes. This equation can be a net positive which means the Carbon stock will increase or negative the losses and respiration outstrip the Primary Productivity. To maximize Carbon sequestration we need to both increase Primary Plant Productivity and minimize the losses through erosion and respiration. In a semi arid area the directing the limited supply of water to Primary Production is important. For instance the water that falls can be concentrated to areas where it will be held. Zai system is an example of this approach. The ability to capture and maintain soil Carbon can also be related to Calcium content and clay percentage which can combine to lower the soil organic matter decomposition rate. The use of permanent covers such as grassland is particularly useful for crop sequestration and the use of forage to crop systems and incorporation of residue and manure return are important and composting is particularly useful for building soil organic matter levels. .Biochar is any strategy which can potentially be used to form both a sequestration and an energy system. To measure soil sequestration a soil baseline of Carbon and Nitrogen are found and as the practices of soil improvement are engaged the Carbon and Nitrogen values are reassayed. The differences in these values will show the sequestration or the losses in vital elements which will either be found beneficially in improved soil or repatriated as greenhouse gases in the atmosphere. This generally requires a long term field experimental approach.
You might want to assess the GPP and/or NPP of the respective soil types.
Dr.Phogat,good question,equally good responses from Dr.Pal and Dr.Hepperly.Longterm experiments offer great opportunity to study carbon sequestration under different soil -crop-climatic conditions.In the recent past excellent work on this aspect has been done in India utilizing the long term experiments being conducted at several agricultural universities under ICAR All India coordinated Research projects under both irrigated and dryland conditions.Apart from literature cited by Dr.Pal,there are many other research papers, review articles ( including Advances in Agronomy),bulletins published from ICAR-Central Research Institute for Dryland Agriculture (CRIDA),Hyderabad. For Dr.Pramod Jha group work from ICAR-Indian Institute of Soil Science (IISS),Bhopal on carbon sequestration one can refer to Researchgate either in my contributions or Dr.Pramod Jha's account.For CRIDA's work one can refer to Dr.Ch.Srinivasarao's contributions in researchgate.Many of their publications are referred in a recent book chapter available in Dr.Srinivasarao publications.Carbon Management as key to climate smart agricuture. By Srinivasarao,Ch. et. al
Dr. Phogat,
You have good question and I think you take good responses from Dr.Pal and Dr.Hepperly.
May be this literature (belov) can help you. Additionally you can try to observation of isotopic C compaunds.
Plant and Soil, August 2007, Volume 297, Issue 1, pp 53–67: Soil organic carbon pools and productivity relationships for a 34 year old rice–wheat–jute agroecosystem under different fertilizer treatments
Soil carbon sequestration means transfer of atmospheric CO2 into the soil C pool either as organic matter and humus or as secondary carbonates.Transfer of CO2 into SOC pool implies addition of biomass C through crop residues, root biomass, manure, compost, mulch etc. to create a positive soil C budget. To calculate the C sequestration potential you have to consider the soil depth, bulk density and change in SOC concentration (may be 1g/kg) over a period of time (may be 5 years) period. In arid and semi-arid climate the C sequestration rate varies between 0.1 and 0.5 Mg C/ha/yr.
It is OK Taradar Ji, but the question is how we may study the maximum potential/capacity of a soil to sequester C under a specific soil and climatic conditions ?
Sequestration of C in soil occurs through creation of a positive C budget.
Cs = (Ci+Cd) - (Ce+Cm+Cl), where Cs is the magnitude of C sequestration over a known period, Ci is the input of biomass-C from retention of above ground and below ground biomass, Cd is the C deposition by run-on and aeolian processes, Ce is the loss through erosion by water and wind, Cm is the loss through mineralisation or heterotrophic respiration, and Cl is the amount lost by leaching primarily as dissolved organic C. ,So to know the maximum potential of a soil you have to choose a vegetation which supports maximum in your studied soil as well as you have to encourage C deposition by run on and the aeolian processes. You need to minimize erosion by water and wind and loss through mineralisation. Rates of SOC sequestration vary among climate, soil type, land use and management. In general the rate of SOC sequestration is higher in cooler versus warmer climate, heavy texture versus light textured soils, deeper versus shallow profiles, poorly drained versus well drained soil, and in foot slopes versus side slopes condition.
Dr.Tarafdar, good comments.To get an estimate of maximum or near maximum carbon sequestration one one has to use/ follow the concept of carbon saturation and stabilization.Dr.Six and his group published several papers on this aspect.Dr.Pramod Jha and his team from IISS,Bhopal have also published some papers on this aspect.One can sample forest soils and also from Longterm Experiments (where manure or manure plus fertilizer is component) in different agroclimatic conditions and dominant soils and get an estimate of carbon saturation nearer to maximum (in longterm experiments) or maximum (in forest) soils.Against these carbon saturation values, the carbon content of other soils can be compared.The degraded soils ,deforested soils,waste lands etc will have more carbon deficiency and they offer greater opportunity to sequester carbon in their particular environments.
Dr. Phogat,
The answer by Dr Rao is what you are probably looking for. Soil C sequestration potential depends on soil's capacity to retain C (saturation concept), which further depends on soil textural composition. To understand the max potential of C sequestration by different textured soils under different climate, you need to set up an experiment. This can be a field or a controlled (to simulate weather) laboratory incubation study, where you use a range of C input (low to very high) and look at the C sequestration. Using labeled C isotopes is very useful here.
Thanks!
Dr.Saha,good comments on important topic of carbon sequestration.I wish to add a few more points relating to carbon sequestration.There should be a baseline established over which one has to measure/compute the carbon sequestration( I have not seen any research study in this line).There will be an upper limit for carbon sequestration(saturation level) in different soils under different land uses and managements in different environments. This has to be established.Carbon sequestration has to be expressed over time span or per unit time(sequestration rate).There is also a dimention of soil depth,sequestered upto what depth of soil .The sequestered carbon is not a fixed entity.Carbon in soil is subjected to decomposition and oxidation reactions.So a measure of emission of green house gases is needed and the amount of loss of carbon needs to be decided/commputed.I agree with the last line of Dr.Saha's comments.Interested colleagues may consult the following interesting publication of Dr.Jha.
Natural 13C abundence and soil carbon dynamics under long-term residue retention in a no-till maize system. by Jha,P. et al. 2017 Soil use and management
http://onlinelibrary.wiley.com/doi/10.1111/sum.12323/full
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