How can we expand the sink capacity of soil for carbon storage?

Dear friends , can you throw some lights on the first part of the question , how does different fertilizer practices help in enriching the soil carbon pool. Do you think , the lower and upper limit of soil carbon pool in a given soil type remain constant or variable in nature . And if it is variable , whether such variation is stable ?

Rajakumar G.R.

Sir,

Pl see:: article entitles "Faster Decomposition Under Increased Atmospheric CO2 Limits Soil Carbon Storage" by Kees et.al., 2014, Science.

https://www.researchgate.net/publication/261834956_Faster_Decomposition_Under_Increased_Atmospheric_CO2_Limits_Soil_Carbon_Storage

Also article

SOIL ORGANIC CARBON SEQUESTRATION

WITH CONSERVATION AGRICULTURE IN THE SOUTHEASTERN USA:

POTENTIAL AND LIMITATIONS by Alan

http://www.fao.org/ag/ca/Carbon%20Offset%20Consultation/carbonmeeting/3fullpapersbyconsultationspeakers/paperfranzluebbers.pdf

Assuming 1.25% of applied N would be emitted as N2O (IPCC, 1997),

N2O 296 times more potent than CO2, aiming at C sequestration to mitigate the climate change will be of no use.

Reamrks pl.

Article Faster Decomposition Under Increased Atmospheric CO2 Limits ...

How does fertilizer practice help or hinder the soil carbon pool?

Do you thing soil carbon pool is constant or variable?

First fertilizer can help or hinder soil carbon pool. Take ammoniated fertilizer since it is very energy intensive it can account for up to 50% of the total energy input is a field crop such as maize or rice. More importantly the footprint is magnified as the stimulation of soil organic matter decomposition leads not only to a high input cost but losses in soil carbon from declining soil organic matter. The use of biologically fixed nitrogen change a soil depleting system into a soil accruing one and reduces the input foot print.

Secondly when amendments are stabilized compost soil accrual will be major in the case of raw manures they will be minor and in the case of ammoniated fertilizer they will be negative sequestration. The biggest opportunity is in simultaneously lowering the input by using biological nitrogen fixation and greatly increasing sequestration by using stabilized organic amendment.

In regard to whether soil carbon pool is constant or variable in some regards it is both constant and variable. If we continue with one set of practices at some point an equilibrium is reached. The equilibrium represents some constancy. On the other hand if we are adding improved practices the equilibrium can be set at higher and higher levels. No tilliage contribution to Carbon sequestration 312 kg/ha Puget and Lal, cover cropping 600 to 1,200 kg/ha various authors, compost applications 1,200 to 2,400 kg/ha, and biochar use depending on the availability and economics.

The systematics of Carbon increase in many ways is only limited by our ability and imagination. In the case of Terra Preto the background oxisol has a soil carbon bank of less than 7,000 kg/ha yet in the areas of anthrosol impacts where char and organic materials were intensively used the same base soil has up to and over 250,000 kg/ha some fourty times the baseline. Since top soil converted through an earthworm has ability to grow upward the idea of a limited chemical equilibrium is somewhat contrived.

Many of the worlds soils are limited by the lack of sufficient clay to complex the soil carbon and conserve it over a more prolonged life. In these same areas they may be sitting on abundant sub soil clay and with its deployment and manipulation with Calcium which also can limit the hardening of the organic reserve this whole equation changes.

Some thoughts.

Sikha Deka

Dr Rajakumar , simple addition of crop residues of organic manures have not been so much paying for longer gains on long term basis. Of late it has been observed that they simply increase soil organic carbon initially thereafter it declines sharply.

It is a very good question as usual. Soil degradation is the most serious bio-physical constraint limiting agricultural productivity in many parts of the world. Yes, soil carbon sink is a major problem in most agricultural soils. Its constraint is particularly important in tropical agricultural soils and subsistence oriented farming systems, where all crop parts are harvested including crop residues. In most agro-ecosystems, sustainable agriculture faces significant constraints due to low nutrient status and accelerated mineralization of soil organic matter. Accordingly, the cation exchange capacity of the soils is further decreased. Under such circumstances, the efficiency of applied mineral fertilizers is very low as mobile nutrients such as NO3-N or K are readily leached from the topsoil during periods of high rainfall. Moreover, soil water retention capacity of soils has been low due to depletion of soil organic matter.

Maintaining an appropriate level of soil organic matter and ensuring the efficient biological cycling of nutrients is crucial to the success of soil management and agricultural productivity strategies. In spite of the application of mulches, composts, and manures having positive effect in enhancing soil fertility, organic matter is usually mineralized very rapidly under tropical and sub-tropical conditions, and thus, only a small portion of the applied organic compounds will be stabilized in the soil in the long term, with most released back to the atmosphere as CO2-C, which has also been mentioned by Dr. Paul above.

Therefore, an alternative to organic amendments is the use of more stable carbon compounds such as carbonized materials. Use of composts or crop residues may not be a serious problem in the emissions of CO2 to the atmosphere in temperate agro-ecosystems as the decomposition of organic matter in such environment is slow. In tropical and sub-tropical environments, use of biochar, composted biochar or biochar-compost mixture appear to be a sustainable solution to enhance soil carbon sink, nutrient and water retention as well as mitigate greenhouse gas emissions.

To achieve this goal, a holistic approach is required involving different stakeholders, including researchers, development actors, policy makers and farmers or producers. Research may play a significant role in the generation and verification of technologies or information which may help enhance SOM, and inform decision makers. Development actors can play a very important role in the creation of awareness and promotion of the practices to communities and farmers. I think this issue is multidisciplinary.

Abdul Ghafoor

I think under arid / semiarid conditions, mineralization of OM is often faster. this questions stands for last several decades. I think fertilizer addition to crops would elevate biomass production which has to help sequester atm CO2. If it is added back to soil surely will increase OM in soil. Now how to increase its persistence in soil needs holistic multi-discipline management as indicated above by Dr. Getachew Agegnehu. To me there will be strong need to develop a compromise between OM addition and rate of it mineralization.

A paper is attached for your considerations.

How can we ensure what fraction of soil carbon pool is aiding towards soil health and plant health?

There is some idea that some of these fractions may be more important that others in relation to plant/soil health. To determine these types of inter relationship since generally as soil total carbon increases so does the labile portions.

From the experience at Rodale where we successful in increasing labile and passive carbon we were able to show its positive influence on reducing damping off, improving leaf blight virus and to improve things like cracking of carrots tomatoes and peppers under fluctuating environments.

For stimulating the plant it is probably a function of labile portions which interact inside the cells itself.

Because the passive pool is so important it would good to develop experimental proportions of both labile and passive carbon and look at the results in an experimental model system.

In terms of plant health the populations of microbes can create a healthy condition which is both dependent of substrate for food and on habitat. Labile carbon can be an effective food while passive carbon can serve as habitat.

In many of the compost tea experiments the effect on disease suppression needed colony forming populations on exp 9 level.

The idea of looking at plant health at different total and passive labile ratios is one that could be fruitful since health is core concern for the quality of food produced from our soils.

When labile fractions are increased from management it appears to be a precursor of later but smaller accrual of passive components.

Excellent feedbacks friends. When there is a organic manure additions in a field , humus is the end product that has maximum resistance , but how far it contributes towards enrichment of soil fertility , remains to be seen . Its good point raised by Dr Rajakumar. Incidently , the stability of humus is constrained by the lower distribution of clay , thereby , renders instability to clay-humus complex , especially in soils belonging to Alfisols , Ultisols , Aridisols , Oxisols etc . Hope Dr Hepperly , you agree with me on this issue . What kind of strategy should we adopt to conserve the organic matter of the soil irreversibly . In that context , Dr Ghafoor raised a very good point that a premise to be reached between OM addition and rate of mineralization .

Improving crop productivity ( For example cereals ) , indirectly contributes towards trapping carbon dioxide ( Kind of carbon sequestration ) and adding to the already existing pool of carbon in soil , but again having stabilized from is the major issue. This is also a debate which fraction of soil carbon pool contributes more actively towards the soil health vis-a-vis plant health?

Paul Milham

I will attempt just the first question, since it is large enough!! Soil C can be slowly built up under permanent pasture (no cultivation). The preceding statement presumes that all plant nutrients are in sufficient supply because they become locked up with the C in fairly predictable proportions. The higher the clay content the better the C is protected. Several years' C storage can be lost in a single cultivation.

Hello. We know that cultivation enhances the loss of soil organic matter. Also, pastures containing grasses and trees, and in particular tropical grasses and trees produce organic carbon that is less lab ile than crop residues.

We also know that soils converted to cropping from forests loose huge amounts of carbon. The overall picture is that only forests can dramatically increase soil carbon storage. The next best option is for ungrazed or sparsely grazed grassy pastures.

Best wishes.

Jeffrey , you have flagged off a very poignant issue . In many of the tropical and subtropical Alfisol, Ultisols and Oxisols areas , soils brought under cultivation by converting the forest lands , tend to loose productivity within few years only . Under such trying conditions , what kind of changes in management strategies , do we need to adopt to sustain the biological quality of the soil without any reduction in crop productivity.

Charles Anukwonke

Dr. Srivastava, A. K.

I would say your questions are too broad but they are well articulated scholarly...

Irreversible carbon management in biotic environment cannot be met since biological communities entertains some forms of metabolic processes following the ecosystemic point of view and ecology. In that sense, continuous soil and water conservation is indispensable to ensure a lasting soil carbon quality/ carbon sequestration ability more especially in marginal soils.

Monitoring and improving soil quality in that view is very important as it relates to crop and plants.

Also a clue could come from the elementary carbon cycle we know as one of the bio-geo chemical cycle where we know about continuum of carbon movement and interfaces

I might mention here that the average age of soil organic carbon in rangelands and forests is several thousands of years. In cropping systems it is a few thousand years. Losses can be fast, but adding resist and carbon is difficult.

Lignins, humins and some highly condensed humic acids are typical of the sparingly labile forms of carbon that are desirable and persistent. Biochar, organic tar and mushroom waste are among the diverse materials rich in these compounds. As far as I am aware, only small quantities of these compounds are produced in broad acre cropping systems. This is the challenge.

Dear Doctor Srivastava

As you are well aware that for a big area of semi arid and arid zone the soil organic matter level is very low based on low primary production and the inability of keeping the humifying materials in place. Organic matter will follow a primary production minus respiration equation. We need to maximize the primary productivity and minimize the respiration and erosion to make these equations work for our future.

To keep primary production materials in the field demand conclusive effort to apply conservation plans on productive areas. We need to apply technologies and management to lower respiration.

Over the millenia the soils in places such as China, india and Southeast Asia did not suffer the declines of New World agriculture due to the practice of using dredgings and returning manures. The dredging combined with manures works to stabilize the soil organomineral complex. While Western agriculture focused on primary productivity through synthetic fertilizer the traditional Asian system of millenia was one of return.

With our modern knowledge we now can approach our food systems with a best of both Worlds approach.

While people have put much emphasis on the effect of the labile short term soil organic which is readily available. The information we have found is that practices that impact short term increases will also eventually be measurable in the long term carbon.

For people in semi arid and arid zones find long points in the topography and that is where the clay and silt reside. Combine this with local organic materials and poit these in areas where the short water can be harvested and these become the grow points as in the zai technology being applied in Africa.

In acid areas it will be important to work with governments farmers and industries to get use of limestone which widespread but not developed in many areas.

I am attaching an article showing the dramatic effects composting with an eye toward the stabilization of the Carbon can have for your information.

In Australia we have many semi-arid areas with low soil organic matter but moderate soil carbon. The 'extra' C is mostly charcoal. Although valuable as a carbon sink, my understanding is that charcoal has only small benefits for soil structure and health. With millions of square km of soils, even 0.5% of charcoal C in the surface is a vast pool of carbon. If crop residues could be carbonised in the field, the 'ball-game' changes completely. Not possible? Perhaps there are niches in which this would work. For example, cotton wastes harvest for biogas production may be charred before returning to the field. Maybe??

Friends , let me flag off another issue . Do you feel bigger soil carbon pool means better crop health / performance ?. What fraction soil carbon pool really dictates the crop performance ?. Does it vary according to soil type and nature of crop , annual or perennial in nature?

Daniel Plaza-Bonilla

Dear all,

For those interested in the SOC-yield relationship I recommend to have a brief look to pages 40 and 41 of the "Managing Soil Organic Carbon for Global Benefits" document that I've attached.

I also include a recent review we published about C management in dyland agricultural areas that could be of your interest.

Hello. I am ALWAYS wary of gross statistical relationships between factors. The relationship between SOC and yield is mainly facilitated by difference in nutrient supply, rainfall and other factors *between* sites. If we compare low carbon sandy soils in the Saharan desert with high carbon clay soils in Texas, we find a statistically significant relationship between SOC and yield. A trivial result, but one that, in milder forms, has been presented hundreds of times by advocates for increasing SOM. Investigations at a given site are not nearly rarely as conclusive. In particular, SOC is a sink for nutrients when it accumulates. There are moderately consistent ratios of N, P, S, K in resilient som, and a significant cost in either fertiliser to replace those nutrients or yield decline due to their storage. It is obvious that nutrients may be introduced by adding som from another site, but that is merely a re-location of nutrients, not a benefit of som per se.

A widely-reported delusion coming som is that it increases plant-available water capacity. This is rarely so, and when it is true, it is a small increase. Decreases are also possible. The lower limit of soil water extraction by plants ( approx 15 bars of tension) is determined by the frequency of minute pores in the soil, corresponding dominantly to the clay size fraction. Hence soil texture, and in particular clay content determines the lower limit of availability. SOM plays no role unless the soil is quite organic (>10%som). Conversely, large pores (0.1 to 1mm, if I recall correctly), dominate the soil water retained at the drained upper limit (approx 0.1 bars). Soil organic matter can play a small role in this value, because highly structured soils have a higher concentration of large pore sizes. However, texture and clay mineralogy are the dominant effects. Well structured heavy clay soils typically hold 45% vol SW at DUL, whereas sands hold 10%. Variation of a few percent in som changes these values by a percent of two, but cannot make sand store the water of a loam, nor a loam store as much as a well-structured clay.

An issue that is sometimes overlooked when considering these things is that som accumulation acidifies soils. The ash alkalinity of the accumulated som is a useful measure of the acidifying effect on the soil. The alkalinity of the som has to be transferred from another site in the soil. SOM accumulation at the soil surface is usually at the expense of subsoil acidification. Other carbon-based chemical reactions can play a role (such as carboxylation) but these are not usually important in unsaturated, aerobic soils. Helyar, Porter and others describe these effects, and soil acidification in general.

In summary, I believe and have demonstrated that it is unwise to make generalisations about the costs and benefits of increasing and decreasing soil organic matter. It is an area of research fraught with confusion, half-truths and sloppy thinking. It is a great joy to see soils that are naturally rich in organic matter and producing high crop yields, but it is unwise to hold the belief that developing such soils is a worthwhile goal. Only detailed agronomy, economics and soil science will reveal the facts.

An excellent logical arguments , you have put forth Jeffrey , lets see what our other learned colleagues have to respond.

The Rodale Institute Farming Systems Trial has been ground breaking in its ability to show that cover cropping and organic amendment in a farming system which weans the crop system from synthetic fertilizer and pesticide dependencies can be both fully competitive in high yield potential but also improve Soil Organic Carbon and Nitrogen significantly.

This increase was quantified as about 1% relative increase for SOC and about 0.5% relative increase for soil Nitrogen on a year to year cumulative basis. One of the chief results was to show that after the transition to the biologically based system the yield of maize and soybean was consistently higher in the SOC and SON improved system than in the conventional row crop system in years of drought after a 3 year transition into the system.

Rhizotrons were set up in the long term trial to directly measure was happening in the root zone. It showed substantially greater proliferation of roots and mycorrhizal spore counts were a magnitude 10 fold higher under cover amendment systems than under synthetic inputs.

The use of biological inputs that confer reduction of soil erosion and increase of soil organic matter are demonstrably more drought avoiding and tolerant. In soybean in these drought years in input plots a 50% yield loss from drought under the biologically improved systems with high organic matter the loss was 20%. In maize under the same years the losses of 30% were just 10%. A robust literature shows that yield potential and stress tolerance can be related to soil organic resources.

For my own experience and looking at these results I do not doubt that while organic matter is not a drought cure all panacea, it does correlate with significant ability to weather them more successfully constituting a wonderful tool and parameter and predictor of good things.

This capacity is obviously very multiple factored but ability to increase the organic matter in soil leads to profound positive changes and water relations is one of these. For instance in the more 33,000 lysimeter readings the results show soil organic matter increases correlates with significantly increased percolation and water retention. The ability of mycorrhizae to work together with plants to extend the root soil superficial interaction also correlates with greater ability to retain soil organic matters in the soil.

I think this attached information will give more depth context of how important this information is for us.

Hugo Rogers

Do all we can to maintain soil quality and keep as much of the world's soil base as we can covered with vegetation as much of the year as possible.

Pedro Cairo Cairo

Coverage by legume plant species. ensuring more active biological layer of soil by improving its structure .Use also plant species as alfalfa (Medicago sativus). Achieving the biodiversity of plant species, silvopastoral Sistems and use of organic fertilizers and biofertilizers

Dr. Roger's comment is very interesting.However, is it practically feasible to cover much of the world's soil base with vegetation? Because, deforestation is increasing at a faster in most parts of the developing world, e.g. in Africa. This is in turn due to increasing population growth and the need for additional land for agricultural purposes, construction of buildings and roads. Don't you think that population pressure is one of the major factors for natural resource degradation? Before 2-3 decades, in most African countries fallowing and shifting cultivation were the widely used traditional soil fertility management practices, but now it has been in most cases impossible because of shrinking land size per capita. Moreover, the scramble for agricultural lands in Africa by large agricultural companies has been increasing since the last decade. I think a very comprehensive approach, including implementable land use and population policies may be important to save our planet from global warming and climate change. Maintenance of soil quality is part of that.

Whats your opinion friends, how soil carbon pool dictates the plant carbon pool and vice-versa?

Ebrahim Hadavi

Dear Anoop,

Almost all carbon in soil comes originally from plant root carbon expenditure in the soils. Plant roots exude large amount of carbohydrates mainly in form of organic acids to rhizosphere which is being used in symbiotic relationships with microorganisms and micorrhizae. Chemical fertilization practices reduce this carbon expenditure as the plant doesn't need to rely on soil counterparts for mineral support anymore. For example N fertilization reduces the root remained in soil after harvest due to induction of more cytokinin production by roots which reduces the root to shoot ratio substantially. This is the direct effect and the indirect effect is that of reduction to root exudation. Even legumes reduce dependence on rhizobia when they receive N directly. Therefore the main strategy which could lead to higher carbon buildup by plants is reducing supply of ready to absorb chemical fertilizers.

The labile carbon pool is the Carbon source for feeding the microbial C pool. Ultimately the ability of microbes and plants will be most limited by scarcity of water. It is the passive Carbon which is mostly associated with that critical water function I believe.

Labile carbon will lead to passive Carbon over time and when it accumulates the water relations will improve both in the physical structure of the soil but also the reserve capacity to store and deliver scarce water.

E Hadavi is right to stress that readily available external inputs have untoward effects on the biological systems. I concur. The ability to promote diverse plant cover will maximize the Carbon sequestration capacity and potential of the soil. In relation to global warming and drought mitigation it is good to focus on accrual in passive Carbon which is key to those effects for top yield potential and as potent of future ability to predict Carbon sequestration labile Carbon pools are good indicators.

The microbial mass and activity active and passive Carbon are all correlated and probably can be used to predict each other.

But such biochar -induced changes in soil organic matter pool will not be active , especially in terms of improving biological properties of soil . Biochar by the virtue of being prepared through pyrolysis is just an inert carbon source . I do not think , it will have any positive impact on the soil carbon sink capacity .

Mohammed Alhassan

Biochar provides unique opportunity to improve soil fertility in a sustainable way. During production nutrients can be retained in the biochar and made available to plants upon application as fertilizer. This is true for biochar produced from high mineral biomass like bone matter. (Alhassan, 2013).

The use of biochar in soil amendment has been described in (Lehmann et al., 2006)

For biochar produced above 3000C, it was assumed that only 80% of the carbon contained in it is stable for a long term carbon sequestration (Lehmann and Joseph, 2009)

The agricultural benefits biochar application to soil include reduction in soil acidity, improvement in soil cation exchange capacity and PH, water holding capacity and improved habitat for beneficial soil microbes. Addition of biochar was shown to improve yield by increasing the soil cation exchange capacity and reducing the nutrient loss through leaching in high rainfall climate (Lehmann and Joseph, 2009)

The increase in biomass yield observed from soil amended with biochar could be attributed to enhanced uptake of minerals by plants due to the biochar applied (Masek et al., 2013).

Mohammed very interesting response , I appreciate it . Similar kind of question was posted by Dr Ghaffor on ResearchGate a week before enquiring about the utility of biochars in rehabilitating the saline-alkali soil and carbon stock of the soil . I sincerely urge upon you , please just go through the discussion took place. It will be eye opening discussion . Biochar can never be a supplement to organic manure or crop residue or any other form of organic matter addition . It will surely add some improvement in physical properties of the soil ,especially in coarse texture soils, could improve soil organic matter as well , thereby , nutrient pool of soil, but how far such improvements will be the part of active pool of soil organic matter , is always a question mark .

Alfredo J. Escribano

Dear Anoop,

Moreover, measures focused on improving soil quality and content of organic matter help. In this sense, management practices based on conservative agriculture (agroecology, organic farming, etc.) will help, such as: mulching, cover crops, crop residues, intercropping, use of orgnaic fertilizers, etc.

Moreover, livestock integration (grazing in low stocking rates) and presence of trees will help.

Check one of my publications that comment on this.

https://www.researchgate.net/publication/280096053_Comparative_Sustainability_Assessment_of_Extensive_Beef_Cattle_Farms_in_a_High_Nature_Value_Agroforestry_System

Regards,

Alfredo J. Escribano.

Chapter Comparative Sustainability Assessment of Extensive Beef Catt...

Thanks so much Escribano , giving another dimension to the already so educative discussion on the subject . Role of grazing livestocks with perennial trees , they not only serve to the ecology , but great tool to favor the restoration of soil quality in terms carbon sink through denudation of depleted lands.

Biochar, produced from biomass, can sequester carbon in soil for hundreds to thousands of years. In addition to its potential for carbon sequestration and decreased greenhouse gas emissions from agriculture, biochar is reported to have numerous benefits as a soil amendment: increased plant growth yield, improved water quality, reduced leaching of nutrients, reduced soil acidity, increased water retention, and reduced irrigation and fertilizer requirements. The quality of biochar as a soil amendment depends on the feedstock type and pyrolysis temperature including soil biophysical and chemical properties. As biochar research is in progress, use of biochar and compost mixture or co-composted biochar can be considered as alternative soil amendments and carbon sequestration. Otherwise, emission of CO2 from the direct application of manure and compost is very high, especially in tropical agricultural soils where decomposition of organic materials is rapid.

Thanks Getachew for your excellent response . How far boichars are microbiologically active to inflict such responses on sequestering carbon into soil ?. Another point of contention with the wider use of biochars is it is alkaline in pH, and holds better promise in acidic soils , hence , may not be so effective on alkaline/or saline -sodic soils. I still remember the response from Dr Ghafoor in this context.

Yes, Anoop you are absolutely right. However, the pH of biochar varies according to the source of the feed stock type and pyrolysis temperature. In most case, biochars produced from woody materials at high temperature (>500oC) are relatively high in their pH and recalcitrant for microbial decomposition, but low in nutrient contents. In contrast, biochars produced from leguminous crop residues and manures are relatively low in their pH, but high in nutrient contents that could be available during application. Carbonization temperature of 350-500oC appears suitable for the production of biochars for soil amendment. Thus, it could be possible to produce biochars that are tailor-made to a particular soil type using appropriate feed-stock type and pyrolysis temperature.

Thanks Getachew , I feel its an excellent feedback , as how to turn up high C:N ratio plant residues into biochars to tailor the micro-requirements of the different soil types , to ensure better effectiveness of biochars. Good piece of information .

Friends , lot of researchers worldover claim , AMs have very strong potential to add seuestered carbon to the labile pool soil organic matter through secretion of soil-related protein called Glomalin. In addition AM-inoculated plants have been reported to experience as much as 10-100 times increase in root volume , could effectively expend the sink capacity of soil for carbon . I remember Dr Hepperly also advocated this idea .

Very interesting response Abhisek . Can we resort to simple principles of conservation agriculture giving emphasis on crop residue retention and reduced tillage , in addition to adopting legume -based crop rotation ?

Husain Ahmad

dear prof, as far as my point of view is concerned, i am currently working on AMF in soil so applying AMF to soil can help plant to crab more nutrients around. your suggestions are welcomed.

Husain, AMs have the ability to bring significant change in nutrient regime (Labile pool) within the inoculated host plant rhizosphere, called mycorrhizosphere. Interestingly , AMs are like plant endophytes , its mycelial network remains confined outside the roots , but ably establishes mycelial network communicated with other donor plants , thereby, offers plants better praparedness to acquire whole range of nutrient like K, Fe,Mn,Zn , in addition to predominantly P, coupled with better plant health on the basis of antioxidant profiles.

I am enclosing my one PDF dealing with Soil Fertility and Plant Nutrition management under organic culture for further reading on the current issue , and invite your further feedback.

Dilip Kumar Pal

@ Dear Dr. AKS - Management interventions through National Agricultural Research System (NARS) wherever followed showed an improvement in SOC status.Our soils have good potential to sequester OC even amidst climate change phenomenon. You may refer to the attached review paper recently made exclusively on Indian soils.

When we project the ability to sequester soil Carbon we can think of the range of Carbon values occurring naturally in soils. In addition, we also can look to optimized agricultural and food systems. The best case actualized scenario is posssibly represented by Terra Preto anthropomorphic soil. These soils developed by the recycling of chars and organic refuse in Amazonian Indian population well before Colombus discovered the new world. While the Amazonian oxisol and ultisols represent a palette of old acid infertile soils to draw upon. The Indian culture was able to convert profiles of high concentration of stabilized Carbon up to 3 meters high. The infertile base has less than 10,000 kg/ha C and in this Indian Black anthropomorphic soils the Carbon supply can exceed 300,000 kg/ha C over 30 times the base amount. In Brazil the remnant Indian Black soil is situated on an area of modern nation state of France. Our ability to store and conserve Carbon globally is optimally represented by that achieved state. With this in mind the ability to eliminate excess atmospheric greenhouse gases is imminently possible and will depend more on a policy and political will than any new technology. Recently on a mission trip in West Africa Guinea state I lived in a small village recently established and the organic base of the village and the village was over 3 meters and this was acheived in just a few generations. The inescapble conclusion is that we definitely can resolve greenhouse gases and ideally the issue is really an exciting opportunity for mankind.

Some excellent factual data were presented by Dr Hepperly , appreciate your efforts for such informative historical perspective of the issue. Abhishek , simple application of organic manures would be sufficient to maintain the required level of organic carbon , we need certain floor management practices , reducing the fallow period to minimum , besides cropping system whose carrying capacity needs to be explored well in advance ....

Loss of carbon sink capacity is not permanent. Composting can contribute in a positive way to the twin objectives of restoring soil quality and sequestering carbon in soils. Applications of organic matter (in the form of organic fertilizers) can lead either to a build-up of soil organic carbon over time, or a reduction in the rate at which organic matter is depleted from soils. In either case, the overall quantity of organic matter in soils will be higher than using no organic fertilizer.

Parameshwar Shirgure

In tropical soils, it is usually very difficult to increase the organic carbon content of the soil. What are the methods through the we can increase the organic carbon content of the soil which is stable for multifunction of the soil ?

I see that different answers relate to organic, semiorganic (biochar) and inorganic (charcoal) materials.

Although increases in organic forms of carbon are highly desirable, these are the most difficult to maintain over time, incur a cost in terms of their unavailable nutrient content, and may have an acidifying effect during accumulation (related to ash alkalinity and functional acidity).

Increases in charcoal content are often less desirable in terms of soil attributes, but are stable, not acidifying and low in nutrients. For these reasons, a soil carbon sink for ameliorating the effects of atmospheric carbon pollution would be best based on charcoal rather than soil organic matter in my opinion.

The oxisols of the Amazon River basin have a low native soil fertility and cannot support continuous cropping. The waste piles of the American Indians in the basin were able to create 3 meters of enriched top soil. The recycling of wastes and ashes seem to keys and the sustainability of cropping on human produced soils is for decades in experimentation. The Amazon Tera Preta will have up to and over 300,000 kg/ha C where the native soil not amended has less than 10,000 kg/ha. It is unescapable to appreciate that these pre Colombian Indians had the answer to our present climate change quandary. The Indians modified areas of an area equivalent to modern day France but in theory this could be extended to much greater areas. In West Africa the top soil accumulation in rich carbon is a similar 3 meters in the village I visited which was only established for the last 60 years. While there is no one solution to climate change the use of soil reservior appears the most proven and feasible. The reduction of fossil fuel emissions by 90% which has offered up is recipe for going back to caveman type of living conditions. In all actuality we need to moderate our emissions but our real soil lution is the sequestration into the earth of the excess greenhouse gases.