Very impressive response Dr Anil Kumar , i appreciate it . Why do have very limited options for green manure crops ?. 

Very important question has been asked by Dr. Kumar, I will appreciate a thoughtful discussion on this topic. I am happy that responses of Raj and Anil indicate that the future discussion on the topic is going to of very high level. Both of them uploaded very good information and answers. My response to various aspects of the question is as under.

* What criteria , shall we use to identify a suitable green manure crop on a given soil? 

Full soil characteristics should be available for which we are going to select a legume. More important are soil texture, moisture and salinity/sodicity level. Please refer to Dr. Anil's answer for more details. If the soil is saline or sodic we can select Sesbania or Ipil ipil. Still in addition to soil characteristics, climatic factors and time available in between crops of the rotation are very important to be considered.

* How do nature and properties of soils come in the way of producing good green biomass?.

If the soil nature matches the legume requirements, not only the legume crop is successful but also the produced biomass, a basic consideration in green manuring, is significantly high and addresses the objective.

* How do green manure crops click with other crop residues in soil fertility resilience?.

Green manure crops have a edge over other crop residue in terms of N fixation and CO2 sink. Moreover, legume residues are tender and take less time to decompose. These also favor microbial population. 

* How can green manure crops compliment   with chemical fertilizers ?

Green manure crops help chemical fertilizers in decreasing additions of N and decreasing the cost of fertilization. Green manuring convert micro nutrients and P of soil into available form.

* How long residual effect of green manure crops could be realized in terms of cropping season ?

Normally, green manuring is recommended after every two or three years but if it well fits in the crop rotation then every year will be more useful.

* Can we expand the overall effect of green manure crops alongside zero tillage?

In my opinion, zero tillage and green manuring do not match perfectly.

* Is there any legitimate policy intervention laid out green manure crops in conservation agriculture?

I do think that there is no legitimate policy of many of governments or any legal law governing agriculture.

Abhishek , everyday , i am feeling increasingly impressed with your style of response , its so overwhelming and so wholesome , that we all find highly informative reading such voluminous material relevant to whatever topic flagged off for discussion . there are another two very important aspects , i want to propose just to take the whole discussion in another mode .  These are : Is there any comparative study comparing the soil carbon enrichment through liguminous green manure crops versus non-liguminous green manure crops? . Very often , it is claimed to store carbon in passive pool and regulate soil fertility  transformation through active pool of soil carbon?

Thanks Dr Nazir for your motivating words and extending the discussion on a further mode . Hope to touch upon some core issues of green manuring vis-a-vis carbon loading of soil . 

Thanks Abhishek for so precious and so pertinent literature for all of our colleagues roped in for the discussion on green manures . hope , we will go through all the PDFs to have further discussion on the subject , which is so educative and informative. 

Which kind of green manure crops have greater capacity to add organic matter in soil- leguminous or non leguminous green manure crops?

Dear Dr Anoop

Answer is inbuilt in your question. Green manuring always done with leguminous crops and it is ancient agricultural practice in India to sequest  atm. carbon. Green manuring adds major and micro nutrients in the soil and improves soil physical, chemical and biological properties of the soil.. At long-term basis, external inputs will be not required for soil health management.    

Dr Anoop,

We thank you profusely for providing the opportunity to be part of yet another important and interesting discussion. It’s a privilege to enrich ourselves with such informative and new scientific ideas and thoughts. We have very limited experience in green manuring experiments and accordingly we would follow the discussions without adding ours. We would like to add a few additional queries to those by Dr Anoop. Should we select green manure crop based on cropping systems? Appropriate crop rotation itself is an excellent way of maintaining and to some extent improving soil fertility and biological properties. But, a few cropping systems may significantly reduce the available nutrient status and biological properties in soil, e.g. potato-based, oilseed-based etc. Do we need to choose the fallow season crop (green manure) accordingly? Secondly, regarding soil properties/conditions should we pay attention to the soil moisture regime at the time of incorporation of the green manure crop? If the soil happens to be in a state above field capacity/saturation should we go for more than one green manure crop (legume + non-legume) as the decomposition would be under mostly anaerobic environment? Thirdly, apart from green manure in the fallow period, do we need to work on cover crops during crop growing season? These thoughts may arise out of our inexperience in the particular aspect and we would highly appreciate to learn from colleagues. Thanks to all.

How do we identify the ideal stage of chopping of green manure crops ? Is it always flowering stage or we can extend further just have more  green biomass.

Yes Dr. Kumar for sharing very pertinent links. We are enjoying discussion floated by you. 

People in North America have been enthusiastic about the work on no till cropping for field crops and the influence it has on soil Carbon and Nitrogen.

Puget, P., and R. Lal. 2005. Soil organic Carbon and Nitrogen. Soil Tillage Res. 80:201-213.

This analysis shows 47 to 620 Soil Organic Carbon gain per year in a long term maize no till monoculture with a Confidence of 95% on the mean figure and range at 320 kg C per ha year.

Doctor Lal suggested that about 10% of the excessive greenhouse gas emissions could be counteracted based on change to no tillage around the tillable acreage.

In the Rodale long term work USDA Beltsville and California work the impact of green manure would be 3 to 4 times that 900 to 1,200 kg C per ha year.

We would have to conclude that 30 to 40% of the Worlds excessive greenhouse generation is potential remediated if cover cropping of green manures becomes standard in the World.

The important concept for workers is that no till and cover cropping can be used together for synergistic benefits. Over 50% of the Carbon Nitrogen input in the cropping system convention is related to Nitrogen fertilizer. The proper cover crop as green manure can eliminate that "need".

The big picture is that mixed farming and use of stabilized Carbon in form of composts and biochar can completely eliminate the excessive state of greenhouse gases potentially in calculated terms.

My opinion stated simply is yes green manure crops can increase soil Carbon and Nitrogen on a long term basis. We need to engage our long term systematic thinking caps to demonstrate and outreach this coming reality which will allow us to mitigate climate change and to improve the yield and quality of our food.

 Let me respond one by one to my learned colleagues. Thanks Abhishek for some exicting PDFs , worth reading for all of us. Non-legume green manure crops fro sure , ahve wider C:N ratio , and , therefore, have extended residual effect  on subsequent crops. this si the reason , such green manure crops  aid in better soil aggregation and mobilising the nutrient pool of the soil.

Dr Ram , appreciating your response.

Dr Brignoli , i do not know , why this practice is still practised with some skepticism?

Dr Nilay , your quarries have worked liking icing the whole discussion  . i do agree with all of your quarries , all of them are so much pertinent in the context of whole discussion . Looking forward the further discussion from our learned friends. 

Application of green manure to any soil is quite a comprehensive natural means to improve soil fertility. Soil fertility is a complex concept, which include all the favourable physical, chemical and biological conditions of soils that support sustainable productivity of crops/plants. Since green manure is not just a fertilizer, but a precursor of the same, which trigger the biological activity, it can improve the physical, chemical and biological conditions of the soil. That is why the green manure is considered a comprehensive natural means to improve soil fertility.

In order to get the full potential of 'green manure application', better we opt for diverse 'green manure' together. This is a complex issue, which our conventional agriculturists have not yet tried or experimented. There are several models of such comprehensive green manure applications, which include a mixture of pulse crops along with manure trees on the borders of the fields, the leafy mass of the same also can be added to soil while the 'manure crop' is added to soil, usually by an 'after tillage'. There is very good scope to research in this field

Responses on this topic are beyond expectations. We are enjoying knowledge and expertise of our learned colleagues. 

Thanks Dr Nazir , lets enjoy the whole discussion , kudos to our learned colleagues with so much of knowledge. Yes , Dr Nazir , i am wondering , how much is the knowledge on green manure crops , our colleagues are having , you must admit that . 

You are dead right Dr Hepperly , cover croppping of green manures , would act like blanket for GHG emissions , besides adding up towards the soil resilience. 

Thanks Dr Ray , infact tillage operation must be carried out after turning the entire green biomass of the crop , much ot the benefit of the subsequent crop and soil nutrient as well as microbial pool.  

I think combination of leguminous and non leguminous types of green manure crops is more remunerative than either of the two  alone.

(1) In temperate conditions, applied organic carbon (OC) was lost mainly as CO2 during green manuring culture, but it was lost as CH4 and CO2 during rice cultivation (Haque et al., 2016; personal communication). Net ecosystem carbon balance (NECB) was negative (-1460 to -1523 kg ha-1) in when green manuring crop was growing, but it increased significantly in rice growing season with greater biomass incorporation rates. The annual NECB equilibriated when 5.5 t ha-1 (dry weight) biomass was incorporated. Positive carbon balance took place only when more than 5.5 t ha-1 dry biomass was added. I think this is not a good option for long-term storage of carbon through green manuring.

(2) Growing GM crops depend on weather conditions and soil properties, especially acidity and salinity. Growing Sesbania sp in summer/wet season of Bangladesh is very much satisfactory, but it incorporation is difficult. So, farmers don't accept it as technology for reducing N requirement and for improvement of soil health.

(3) We can save 40-60 kg N ha-1 if 12-15 t ha-1 GM biomass is incorporated for rice crop cultivation.

Good point , you have raised Dr Deka  to realise the impact of green manure crops , especially the residual effect other crop seasons. I am still to get responses from our colleagues , how , we can realise the effect of a green manure crop  , is residual effect carried forward to subsequent crops?

Thanks Dr Biswas for an enlightening response , worth appreciating . This is where th e multi-fold effect of green manure crops lies. 

Let me float those quarries once again , which Dr Nilay proposed in his response , they are truly genuine . Friends , i request all of you to please respond;

*Should we select green manure crop based on cropping systems? Appropriate crop rotation itself is an excellent way of maintaining and to some extent improving soil fertility and biological properties. But, a few cropping systems may significantly reduce the available nutrient status and biological properties in soil, e.g. potato-based, oilseed-based etc.

* Do we need to choose the fallow season crop (green manure) accordingly? Secondly, regarding soil properties/conditions should we pay attention to the soil moisture regime at the time of incorporation of the green manure crop? If the soil happens to be in a state above field capacity/saturation should we go for more than one green manure crop (legume + non-legume) as the decomposition would be under mostly anaerobic environment?

*Thirdly, apart from green manure in the fallow period, do we need to work on cover crops during crop growing season? 

Dr Anoop,

Thanks for your gesture and initiative. We would really like to learn from colleagues their experiences. We had an observation from very brief (2 years) experimentation on cropping system, where some of the rice-legume (e.g. greengram, field pea, ricebean) cropping sequences could not outperform rice-wheat, rice-rapeseed sequence in terms of population of Azotobacter, phosphate solubilizing bacteria. We understand that this is not the sole parameter for judging cropping system, that too in such a shorter period. But, having potato as a component crop in the cropping system has the worst impact on soil biological properties under long-term cultivation, which is also substantiated in several reported works. Thus this thought of suitable green manure based on cropping system had been shared. Wish to learn more from experienced colleagues. Thanks.

Nilay, your quarries are of very good nature. They deserve to be addressed. That's a good point, but how far it is genuine to select  a cropping sequence simply on the basis of changes in biological properties? 

Let me try out responding your quarries Dr Nilay. 

Should we select the green manure crop based on cropping system : This  is where the success of cropping system as  whole and role of green manure come complimentarily with each other. No , doubt , some cropping systemsare so effective that you really do not need any additional green manuring . But some croppping system , especially where legumes are not the part of it ,  green manuring needs some intervention 

Do we need fallow season for green manure crops? depends on the moisture conditions and the type of green manure crop choosen . But some fallow is needed to accomodate green manure crops so that subsequent crops are benefitted out of such practices . Soil moisture in this regard , holds most pivotal role , otherwise who will distintegrate /decompose the  green biomass ? I have been repeatedly expressing , tim ehas come to have some standards for classification of biologically active soils to non-active soils. This could be with respect to particular soil , cropping system or farming sytem .

Cover crops have their own utility ,. We need to have clear cut distinction between the usage to cover crops  green manure crops.  We can still afford to live with cover crops , but green amnure crops have to decomposed at the earliest to harvest upon the nutrient release and organic carbon -triggered  elevation in soil  microbial activity   .

Hope , you find these answers convincing 

I think long term effect of tillage  along with green manuring in influencing the soil carbon pool is mandatory to look at success of a cropping system in a farming system mode. 

Dear Anoop Kumar Srivastava ,

These are all in Practical Application of Green Manure in the Field,

 1 ) In Padi Field before Start the Cultivation,

Applying the Green Manure  =  Neem tree Leafs with flexi-stem ,

Portia Tree Leafs with flexi-stem, Raom Tree Leafs with

flexi-stem.

2 )The Same Field After 3 + 3 Months Crops ,

then Cultivating Ground-Nut Crop But after the Crop maturity ,

these as Used as Green Manure ,

these type Cultivation is Two Benefits without Idle the Land .

Its good Crop Rotation . Land Issue not been so far.

Dr Parameshwar,

Complements to you for your comments. Your observation is well agreed upon, as was mentioned soil biological parameters can not form only criteria for judging the performance of cropping systems.

Dr Anoop,

Complements to you too for your justified comments. Obviously, the fallow season needs to be better utilized through green manuring. We would just like to learn the effect of mixed green manure crops on soil properties instead of single species. Accordingly, would there be any difference in soil properties between diverse weed flora and a few weed species during the fallow season? Thanks a lot for your response.

Yes there is every possibility to look into weed composition versus mixture of green manures crops.How long any change in soil SOC sustains  in a cropping system.

Thanks Dr Nilay for an updated , but very practical response.  i agree with you to have a study about how composition of different weed flora and biological properties of soil undergo changes in response to mixture of green manure crops. same was raised by Dr Deka as well.   

Dr Barbora , thanks for very thoughtful response, do appreciate . 

Binoy Medhi to you18 hours ago

Carbon sink through green manure is now a days a new venture for sustainable productivity of soils. Owing to wide C:N, C:P ratio of green manure crop it reflects the high rate of immobilization process encouraging carbon build-up in diversified soils preferably in light textured soil type. A long term study in acid soils of Assam revealed that application of Green manure crops like Sesbania aculeata, rostrara help in building organic carbon by about 0.10 to 0.22 percent over a period of 15 years.

Iuliana Florentina Gheorghe to you14 hours ago

Manure is a very important fertilizer because it is a source of nutrients (N, P, K, etc.). It is also an important source of carbon by organic matter which is an important source of energy in processes of synthesis of humic acids, denitrification processes, nitrogen fixation, etc.

As opposed to synthetic fertilizers NPK, the manure is more complex and releases gradually the nutrients. The processes it is similar which litter decomposition.

Xiaohui Zhou to you  3 days ago

*To identify if the green manure crop is suitable or not on a given soil, you should also take into what kind of plant will be planted, as different material need the type and quality of fertilize are quite different.

*when green manure are broken, they can better the soil not only in terms of fertilization but also help to make a balance of microorganism in soil.

You can make a control that in a given soil, plant the same material, and one part of the given soil is added with green manure, and the other one is as a control.

Friends , these are few responses , i received from our colleagues , so i thought , let me load all of them for ours benefit and have a further discussion on the issue. These messages were not visible in the main stream responses. ...

Yes I agree with both  Luliana and Xiaochiu, manures have a very complex pattern of nutrient release. This is the reason the residual effect of manures is more expanded than inorganic fertilizers. 

Let me throw some more light on the integration green manure crops in crop rotation , Dr Nilay , your favourite question . Green manures fall into two basic types when considering where to place them in the rotation. Examples of the first type include grass/clover leys, lucerne and other long-term fertility builders that are used to provide the fertility foundation for a period of cropping. The duration of the fertility crop and the subsequent cropping will both depend on a number of factors. A key factor is the inherent fertility of the soil – where this is good the cropping period can be maximised. Other factors include the type of cropping – if this is a combination of field vegetables and cereals then the fertility crop can be undersown into a cereal at the end of the cropping period.

This should ensure a more reliable establishment of the ley and avoids the need for autumn cultivation. This can be a problem where the fertility crop is being established following a vegetable crop. This crop must be cleared early to allow time for establishment of the ley otherwise a spring sowing will be necessary. There is a growing interest in the idea of undersowing into vegetable crops (e.g. red clover into sweetcorn) though more work is needed before reliable recommendations can be made.

To identify if the green manure crop is suitable or not on a given soil, you should also take into what kind of plant will be planted, as different material need the type and quality of fertilize are quite different.

*when green manure are broken, they can better the soil not only in terms of fertilization but also help to make a balance of microorganism in soil.

You can make a control that in a given soil, plant the same material, and one part of the given soil is added with green manure, and the other one is as a control.

Thanks Dr Anoop for the input.

Dear Anoop Kumar Srivastava

You have pointed several good points about age-old useful practice for the sustainable production of safe foods with harming or altering the biosphere equilibrium. I could try to address some of your points. The scientist have given a good treatment to the questions. 

* What criteria shall we use to identify a suitable green manure crop on a given soil?

i. Crop that can fit in the main crop rotation, e.g. in rice-wheat rotation a crop that can be grown during May to July is Junter, Guara etc.

ii. Crop should be fast growing to with less fertilizer and water to provide reasonably large biomass.

iii. Under arid-semi-arid region calcareous soils, deep rooted crop have capability to accumulate Ca preferably in biomass.

* How do nature and properties of soils come in the way of producing good green biomass?

Unfavorable season (e.g. heavy rains for Guara, very dry season for Junter); fine or sandy soils, soils having hard pans in the sub-soils, rocky and/or soils on high slopes may the crops adversely.

* How do green manure crops click with other crop residues in soil fertility resilience?

I am not sure but possibly GM will favorable affect soil fertility resilience.

* How do green manure crops contribute towards carbon pool of soil?

After partial or complete decomposition, ultimately will improve soil carbon pool, however, amount of biomass will matter too much.

* How can green manure crops compliment with chemical fertilizers?

* How long residual effect of green manure crops could be realized in terms of cropping season?

Since plant biomass will contain all the essential and non-essential, known/established and unknown nutrients will considerably decrease the synthetic fertilizers requirement not only of the following crop but the residual may last for 3-4 years.

* Can we expand the overall effect of green manure crops alongside zero tillage?

I expect that zero-tillage might not be suitable for green manure receiving soils since biomass decomposition needs O2. Otherwise, an-aerobic decomposition may lead to the production of unwanted gases (methane) and other compounds (CO3, HCO3) those have environmental implications. Hence reduced tillage may be suitable. You may consult Whittig, Starkey, Janetzkey etc on anaerobic OM decomposition.

* Is there any legitimate policy intervention laid out green manure crops in conservation agriculture?

I do not think so anywhere. Even conservation agriculture is in its infancy, needs lot of awareness among farmers and policy planners for its promotion. Here in Pakistan, there was no Abiana Charges by revenue department on green manure crops during sixties and seventies those now have been imposed.

Fasinating response Dr Ghafoor , with a crystal clear concept .  I need the intervention of Abhishek and Dr Nilay  both  and other learned colleagues as well.  Green manure crops have the adaptibility to wide range of soils , including the calcareous and salt affected soils . I do agree , green manuring and zero tillage will find some difficulty in complimenting each other . Is there any possibility to prolong the residual effect of green manuring by modulating the soil carbon pool ? . Thats very interesting to listen the residual effect of green manuring , lasting for about 3-4 years. 

Pl have a look of following links regarding the residual effect of GM.

https://www.google.com.pk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwj2vcmIssfMAhXIcBoKHQXSC70QFggkMAE&url=http%3A%2F%2Feprints.hec.gov.pk%2F376%2F1%2F236.html&usg=AFQjCNG5henkkfOCEtrdYP_02YaHWRVJjA&sig2=Uzf4O1OOURvpMZI03udafA

https://www.google.com.pk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=0ahUKEwj2vcmIssfMAhXIcBoKHQXSC70QFghBMAU&url=http%3A%2F%2Fwww.pakbs.org%2Fpjbot%2FPDFs%2F42(5)%2FPJB42(5)3125.pdf&usg=AFQjCNFTsvMQJESoAayFvFPvwUdrcNhZTw&sig2=4-solh1dPTwjwmoAIYwLZQ

https://www.google.com.pk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0ahUKEwj2vcmIssfMAhXIcBoKHQXSC70QFggvMAM&url=http%3A%2F%2Fwww.pakjas.com.pk%2Fpapers%255C1059.pdf&usg=AFQjCNGTVmsq12LzS_cQlRRDqg-e1Xz2-w&sig2=9WJ3xRCeCY2aBo3lhlk8xw

 Thanks Dr Ghafoor for some interesting links , worth reading .  The residual effect of  green manures or any other manure is judged by the magnitude of response of succeeding  crop in a rotation . Is there any deciding  parameters through which  , you can measure the effectiveness of response of residual effect of green manures or any other manures as a matter of fact ? 

Residual effect of green manure is a complex process largely depends on the rate of mineralisation and immobilization. This is again dependent on C: N ration.

Iappreciating your response Dr Deka , let me add some more useful feedbacks to extend the discussion further:

Specialised crop farms where the use of animal manure is limited, green manures provide the most effective way to improve the nitrogen supply for succeeding crops . The inclusion of perennial leys in crop rotations is regarded as an important tool to increase soil fertility due to the positive effect of leys on soil organic matter (SOM) . Cultivation of legumes results in an increased mobility of phosphorous compoundsin the soil and enriches the soil with organic matter too. The largest amount of organic matter is left in the soil with the residues of perennial grasses The productivity of crops depends on soil properties, meteorological factors, fertilisation, and particularly humus content in the soil. When the soil is poor in humus, crop yield is even more dependent on the natural conditions – heavy-textured soils in wet years tend to become lumpy, whereas light-textures soils in dry years become moisture-deficient more rapidly and plants are prone to wilting.

 The study was aimed on Albi-Endohypogleyic Luvisol (LVg-n-w-ab) to explore the residual effect of phytomass of differently-managed perennial grasses, as green manure, on the improvement of soil properties and on the productivity and phytopathological condition of spring barley grown in a crop rotation in the second year of effect. The greatest amounts of plant residues were found to be left in the soil after differently-managed lucerne (19.48 and 17.29 t ha-1) and red clover of the 2nd year of use (13.06 t ha-1). With phytomass, the soil  received 294.6, 262.6 and 228.2 kg ha-1 of nitrogen, 31.0, 26.5 and 24.8 kg ha-1 of phosphorus, and 154.2, 133.6 and 129.3 kg ha-1 of potassium, respectively. The C:N ratio of the aboveground mass of perennial grasses was thelowest and more favourable for a more rapid decomposition (10.0–14.0) than in the residues (roots and stubble) (20.0–36.0). Nutrients, released during mineralization of phytomass of perennial grasses of the second year of use, had a positive effect on spring barley grown in the second year of effect after green manure incorporation. The correlation of spring barley total stem number, productive stem number and grain yield with the content of organic carbon formed by perennial grasses was moderately strong and strong (r = 0.504*, 0.640** and 0.727**, respectively). The correlation of spring barley productive stem number and grain yield with the content of available phosphorus formed by perennial grasses was moderately strong and strong (r = 0.506* and 0.790**, respectively). Available potassium content in the soil influenced only barley grain yield r = 0.548*. The severity of spring barley foliar diseases  ignificantly depended on the growing conditions: P < 0.05. A 1.1–1.2- time higher foliar disease incidence and severity was recorded in the agrocenoses of spring barley after legumes of the 2nd year of use, especially after lucerne. The total and productive stem number of spring barley significantly increased the severity of foliar diseases at barley booting and milk maturity stages (r = 0.455*, 0.502*, 0.905** and 0.834**). However, the severity of foliar diseases did not exert any significant impact on barely grain yield and 1000 grain weight.(Skuodiene et al 2012 , Agriculture 99: 237-246). Full PDf enclosed for further reading friends. 

Is there any study available  comparing the response of green manures    by mulching, digested residue and compost. The amounts should be based on the same  amount of nitrogen, carbon and available nitrogen in soil . 

How does the residual effect of leguminous residues differ from nonleguminous residues with regard to mineralization rate as well.

A very pertinent issue , you raised Dr Deka. My compliments to you . Yes i agree with you . there will colossal difference in not only the rate of mineralisation of liguminous residues comparing non-liguminous residues , but dynamics will also be distinctively different . Narrower C:N ratio of liguminous residues brings changes in nutrient pool much quicker and richer , besides microbial diversity than non-liguminous residues.  

In the light of above discussion , we often raise the issue of time frame for which different organic residues will produce distinctive effects on soil health and crop health in terms of residual effects..? Is there any study carried out in the past..? 

 Let me  toss up another quarry to all of you,  friends .   What is the true value of crop residues when used while incorporated into the soil as adopted in case of integrated soil fertility management  and conservation agriculture where crop residues are left on the surface of the soil ..?  What kind of change in nutrient dynamics be expected under two contrasting soil conditions through two different concepts of nutrient management ..?

The ability to conserve the soil life blood is dependent on first greatly reducing the soil erosion rate. Secondly improving the soil organic matter and nutrient balance of the soil. The use of residues as soil covering is very critical for that first step. In addition the residue material can be of great utility for weed control as many of the annual weeds need direct sunlight to stimulate their germination and emergence. The management of green manure covers can be the most critical step of the biologically based cropping system. Since the use of ammonium fertilizers can have such drastic effects in acidifying soil and stimulating decreased soil organic matter decomposition is critical. The use of legumes for improving Nitrogen cycling and content are the center of a cropping system that is both sustainable, profitable and improves the soil.  The wisdom of this approach is extended when permanent perennial plants support an animal component. Mixed animal and plant production systems is the way nature is designed and most efficient and ecological.  Since the problem in the soil is the disappearance of organic materials the use of technologies which lead to conserved and improved organic matter is another key. Composting of residues and manures and use of char seem to be the powerful tools in our tool chest for that link in this chain. We have a menu or methods to resolve the important issues addressing our food system and environment. What we need is more will to implement known methodologies. The bottomline is our report card for this endeavor is the soil status and we need to manage the systems according to the ability to optimize that report. 

Thanks Dr Hepperly . We were heavily missing your touch of excellence  in many of our discussion . Hope , you will keep us updated with your excellent inputs. At last , you have touched upon the report card . How effectively could it be developed in the context of on-going discussion . Most of the researches claim , best organic residues are those , which have slow rate of mineralization , in order to secure better carbon loading  in the soil. 

I like a greenhouse gas report card.

First, take all you input practices and put the emission Carbon values on them.

Second, monitor all the Carbon positive practices and their value also.

Third, measure the net result is like profit and loss analysis but applied to the agricultural system.

Forth, proactively modify and test modification to the agricultural system. 

In maize cropping system  for instance over 50% of the emission input is from Nitrogen so that is the big ticket item.

Hence the need to focus on legumes in an input sense. In the sense of sequestration most workers and farmers do not realize that is big item the inputs are lesser change.

If our system is not accruing carbon from the degraded states most agricultural fields are in we are not in business. Sustainability unfortunately will not float the boat of improving the productivity of the system let alone address the need for better atmospheric gases into the future related to climate change or mitigate periodic drought issues.

Bottomline is that the soil is the bottomline.

To work this way we need a baseline assessment and on going mointoring of the acrual or lack of accrual in our soil carbon while sustainable is not going to resolve any of the issues plaguing our World.

As such we need to dynamically set goals and make adjustments. This will need a quantum jump from the researchers, extensionists and farmers alike. 

We will become the Carbon farmers who can resolve the big issues plaguing our modern societies. 

Green manures have the definite merit to expand carbon sink of soil but it remains to be tested how long that stored carbon is stable following the subsequent fertilizer practices.

Good point  Dr Deka , and well responded by Abhishek . I solicit the response from our other colleagues on this issue .  

Dr. Srivastava, pertinent question!

My query here is, what is the length of time you are referring to here in the question??

Generally, in discussion of carbon sequestration, 'long term' means 'multiple years' may be more than a decade (I believe).

The carbon stability and saturation depends on the nature and content of the clay in the soils under study.

Also, vegetation materials do not last for 'long term' in soil, specially green manure crops which are already high in nitrogen.

Green manuring crops are chosen to decompose immediately owing to their narrow C:N. C is consumed along with N.

Let us discuss what you think.

Regards,

MKD

The long term means usually more than a decade. The effectiveness of green manuring is dependent on a stage of harvesting with a C:N ratio. But, how long the increase in carbon contributes towards the carbon reserve pool of the soil, is most important, whether it is green manure or any other organic manure. 

Dr Shirgure i agree with your feedback . We need to expand  sink capacity for storing carbon in soil  through both labile as well as non-labile pools , but regulate soil fertility through labile pool of soil carbon only , thereby , non-labile pool acts as a real reservoir for carbon storage in soil ..?

Your concern is very important , how long carbon accredited into the soil through turning green biomass into soil , contributes towards the carbon sink of the soil. 

Organic soil amendment, no and reduced tillage, cover cropping and liming acid soils can all contribute to long term increases in soil organic matter. These differences are shown in long term experimentation which is not available for most individual researchers because of the lack of long term demonstration trials. Optimizing the legume component of a farming system is extremely important since the Nitrogen application for cereal cropping has a long negative impact based on its generation of long amounts of acidity into soil environment, the environmental costs associated with its loss to water, the impact on greenhouse gases loss to air  cost and its potential to stimulate loss of soil organic matter. The use of legumes in the cropping system largely eliminates the long term issues from the Nitrogen fertilizer issues. Putting the various practices together in an integrated crop and animal production system is science and art and is verified through conscious scientific effort to improve and understand the Farming systems and the processes in them. Our research and educational system is behind in their support and use of these long term efforts so critical for our ability to engage our food system to resolve our societal issues of nutrition, economy, environment, energy and climate change and mitigation needs.  We need to integrate legume cover cropping and legume cropping into or crop and animal systems to regenerate our soil resources to address an improved food future for our growing population. 

Thanks Paul for putting up  a very comprehensive response indeed. I agree with you  in totality . We need to emphasise the livestock production system , since it accounts for as much as more than 15% of  total emissions accruing out of agriculture . 

New corners have been enlighted by the Scientists, thank you. 

Thanks Dr Nazir , we all learn from each other in heaps , hats off  to you all friends for digging out the science like this....

I agree with Dr Paul, we need to introduce legume crops and legume based cropping system. Time of harvesting is very important if full potential benefits of green manure is to be achieved.

Dr Deka , you are  absolutely right . If you remember , Abhishek raised the issue of evaluating different green manure crops in both , conventionally and non-conventionally adopted crop rotations on different soil types  and under different seasons , using their short duration options ..? We need to debate this issue more comprehensively..?

The issue being discussed here is quite pertinent to the discussion. I am looking forward to the further discussion raised by Dr Srivastava. 

thanks  for appreciating Dr Shirgure . This is the very purpose of learning from each other . Hope , we will continue such discussion . 

Incidently , green manuring is one of the ways to keep the best soil health , not only from the point of view of soil ecology , but ensuring the optimised soil fertility for much better crop performance , in addition to one of better ways of carbon sequestration in soil through better  net photosynthesis of green manure crops.  This also aids in increasing the use efficiency of applied nutrients.  i appreciate your contribution Abhishek , keep it up. The discussion is really inching towards peak....

Very well said Abhishek. Very articulative response . Green manuring has multiple roles, unfortunately , we have been comprehensively missing this age old practice , more so as its  utility as cover crop....

Studies on carbon stability added through different organic manure sources is most important. I hope colleagues will agree with me. 

One of limitations of green manure cropping is that use is not much taught in comodity farming systems of advanced economy academic environments and there is little incentive available to encourage farmers fo use it.

 My opinion is that teaching demonstrating and giving monetary incentive for Carbon sequestration proven could be a game changer. 

No till has been championed by corporate interests but they have not gotten on the board related to cover cropping. When a legume cover crop is employed it can reduce or eliminate the use of Nitrogen fertilizer and the corporate interest is often focused at the inputs as solutions when many times they constitute part of the constraint. 

One of the biggest limitation of biologically based farming systems is their mechanism are not well understood and the systems are not simple like a aynthetic input system approach. 

Thanks Anil Kumar  for good feedback . This was the very aim of tossing up such a question , since we have been comprehensively overlooking the  the multiple roles of green manuring , so well proven agriculture practice  almost at the verge of forgotten practice in farmlands . You have rightly said,  and i agree with Paul as well , our academic curriculum needs revisiting with emphasis on biological system of sustaining agricultural productivity . 

The dynamics of the green manuring needs to be reinforced and sensitised at various academic levels. Paul you are very right. 

One practice that can help in this regard of green manure utilization is the support of public institutions such as higher education and government in producing and selling green manure crop seeds of improved varieties with local and regional adaptation at competitive prices.

This ideally will be reasonable for both the public institutions and the farmers and since this is rather specialized multiple national corporations should feel infringed by the practice. The utilizing of this system will allow the crop improvement by classical methods not be lost which has been occurring in North America. If India could do that it would be great for India and the World

Thanks Paul and Shirgure  for uploading some nice concepts , as how can we popularise the concept of green manuring , a dying practice in agricultural fields these days, unless warranted mandatory , especially confined only to experimental fields...?  

In high cropping intensity areas, growing green manuring crops for soil health improvement only is very very difficult. Mixing of large green biomass is the main reason among many others. Cheap but effective equipments are needed along with monetary benefits might help in this regard.

Dr Biswas , the fact is , in high cropping intensity areas , there is hardly any  opportunity  for accomodating green manure crops, since there is no fallow...? 

Sometimes,  translating improvement in nutrients as  a capital of the soil,  is difficult to translate into economic returns... 

Dr Anoop,

I fully agree with you that soil health improvement can not be translated into economic return; but then consider the fate of farmers who produce the crops and sometimes bound to sale it even under the rate of production cost. The benefit goes to middlemen. As a farmer, why they will invest in losing enterprise even though their future generations might depend on soil-water resources?

Dr Biswas , the improvement in nutrient capital of soil is such an attribute that works so invisibly towards the betterment of the  crop untirely , but very difficult to quantify the contribution , hope you also agree...This is where , we have distinctively failed to address the multiple  roles of soil as ecosystem service provider...?

Green manure works to keep the ground covered and greatly reduces issues with wind and water erosion.  

When erosion is not controlled it is very difficult to build soil.

First as a medical doctor would say you have to stop the bleeding. For the farmer agriculturalist this is of primary importance.

When Nitrogen is short the development of humus is curtailed the legume green manure addresses both of these controlling erosion and providing Nitrogen. Because of the superiority in nutrition the legume stimulate much higher earthworm populations.

In terms of regenerative agriculture the legume component needs to emphasized. In terms of soil water relation it is mostly a function of increasing soil organic matter 1% soil organic matter in 100 dry weight units of soil can absorb and recycle less that 30 units of water when soils are regenerated to over 5% the natural virgin condition it can recycled and absorb over 200 units of water in the same 100 dry units of soil. Tha action of the soil organic matter is to make the soil more porous and expands the spaces for air and water to be facilitated to the root system. Humic substances at low concentrations of parts per million stimulate much more aggressive root growth. The root growth is the most important factor in the crop system in maintaining and increasing soil organic matter. Finally the use of compost amendment can greatly increase the ability to increase organic matter as well as rotation animal production with plant production systems. Together these practices are capable of reversing the enrichment of greenhouse gases and if implemented across the global landscape can neutralize the threat of climate warming and improve the productivity and quality of our food. 

Good stuff Paul , highly motivating to learn about the multiple roles of green manure for not only sustaining the soil health in a intensive cropping system , but also  counter the negative consequences of greenhouse gases. Another important  issue is , how to adjust the duration of green manures under a concept of intensive cropping system , where soil is hardly under  fallow ,,,?

The success of green manuring is decided by the season in which is grown and the stage of harvesting in addition to soil acidity or alkalinity. 

Ideally the farmer grower worker first step is to sample the sample and remedy the basic constraints with physicial, chemical or biological. The determination of nutrients, pH organic matter and compaction layers all are critical. After the development of plan and practice to address these a system of rotation farming directed at both achieving the long term goals of optimizing the soil and achieving the economic ecological and energetic outcomes desired is formulated. If this is done according to a plan it can foundation of certified farming which can separate the grower in a market place. Parameshwar Shirgure you are right that seasons are important and stages of making operatuion and the adjustment of soil characters according goals and wishes. When farmers and worker really care they will become one with the soil they till. Some people only see agriculture culture of the field as a scientific and technological exercise but I believe the experience is much more spiritual than simply material in its ideal focus. 

Dr Paul, I am very happy with your reply. Whether biomass of green manure is more important than stage of the crop from adding carbon to the soil as a carbon sink ?

Thats very good question Dr Shirgure , where shall we compromise , address at the correct stage of harvesting or biomass production , though at alter stages, fibre yield is higher than harvesting the crop at flowering stage,....?

When it comes to the ability to build organic matter the critical factor is the amount of roots produced. The roots are much more recalcitrant which allows the input to exceed the decomposition. Prairies as natural ecosystems are astounding for this particularly mixed grass, legumes and composites are particularly critical. To get the deep profound effect the ley cycle should employ perennial mixed species and the duration of a perennial phase can be balanced with a cropping phase giving soil building potential and allows for the control of both plant and animal diseases and constraint. To build soil with annuals the retention in the field to mature stages allows more benefits than short cycle annual green manure. 

Very interesting question, and well discussed. Definitely as discussed by Dr Jatish Bswas GM helps to the succeeding crop or group of crops within cropping system, but the question on long term basis for tropical/sub-tropical regions where the OC degradation might be at faster rates, but if the practice followed on regular basis might be beneficial to the system but if stopped, might be the OC may come back to its original value, very tricky question. Prevailing weather and inputs management could play a very important role

regards

Dr Naveen I agree with you. The biggest issue is how to make improvement in organic carbon content of soil into the permanent pool of soil carbon..

Good point Dr Kalra, you raised . Our experience also advocates the same philosophy , with citrus. We were able to increase organic carbon content of the soil in the first five years of experimentation , then decline stared and by the end of nineth year , soil organic carbon recorded that value , where we started . What i want to say , that what can be done to translate that increase in carbon content of soil to become this carbon as a part of non-labile pool   with cascading effect on labile pool of soil...?

As the key to improving the soil organic matter pool is not so much the ability to capture Carbon from the atmosphere but more related to improved retention of captured Carbon to prevent its re release back into the atmosphere. The ability to have a higher equilibrium Carbon in soil is a function of clay and Calcium is critical.

The organo mineral complex can be bioengineered by the reaction of Calcium with clay and oranic matter. The cation bridges which Calcium provides combine with  the overall negativity electrostatically of both clay and organic matter in this reaction to form a complex of enhanced persistence and action in the soil.. The reacted complex is chemically and biochemically stabilized so that retains it in the soil organic matter because of the greatly reduced decomposition rate.

Fortunately in a global sense there is no real deficiency of either clay or silt or Calcium critical reaction ingredients. Another viable strategy is the emphasis on new generation of compost which employ the organomineral complex to created more stabilized compost and to use manure for producing this type of compost.

In addition to organomineral complex biochar has retention capacity o give the long term changes in soil equilibrium which would not have the limitation of some of the other strategies. 

Some very good points Paul . Our strategic changes in exploiting the synergy between clay-humus complex using cation bridging  and calcium , could bring some distinctive changes in capturing carbon as a permanent pool of soil carbon reserve. Our experiences say , any improvement in organic carbon content as a result to organic manure additions have failed to inflict long term consequential  improvements in soil physico-chemical or biological properties  , simply because of our inability to retain the carbon additions towards the non-labile carbon pool of the soil..?

Dear Anoop, What is the equilibrium soil Carbon values you obtained after 9 years? If you have a complete analysis of the soil I might have some suggestions related to possible approaches to stretching the limit of the Carbon sequestration related to your condition. Thank you again for the insights your forum questions bring up. Best Regards, Paul Reed Hepperly

Paul , when we started our experimentation on Vertisol , the initial soil organic carbon was 4.58 g/kg , and after nine years of experimentation  , soil organic carbon was 4.72g/kg , but after first years , the value was 6.20 g/kg , then it declined to 4.72g/kg using vermicompost  application( 15kg/tree /year) in  mature citrus  trees ( 10-years-old plantation) under clean cultivation.  We need to develop quasi-equilibrium for each soil type with specific crop. One of the possible approaches could be the orchard  floor management  using minimum tillage /green manuring /residue management /cover crop interventions etc , to see how how the dynamics of carbon partitions between labile and non-labile fractions of soil carbon. 

Dear Anoop, Your soil organic matter level is indeed low. The use of vermicompost is not as stable is not optimized for the purpose of raising soil organic matter. Instead try using  leaf or straw compost supplemented with Calcium, Phosphorus and modest amount of manure. The use of manure in our experience is much less effective in raising the soil organic matter. Take a look at the Calcium and Silica levels which might be limiting your ability to accrue organic matter. Plants such as Mucuna deeringiana is particularly good at soil organic matter accruing. The basis of this is probably that fact that Nitrogen is not limited and the high level of plant melanin from the velvetbean Mucuna deeringiana metabolism is highly resistant. The crop before the citrus could well be advised to use the velvetbean to to increase the soil organic matter and control nematodes and plant pathogens before the citrus is transplanted. In advance to transplanting prepare leaf manure compost with Calcium and Phosphorus for the use in the planting holes. Use the wood or straw surface mulch around your trees is advised. This will lower soil temperature and control weeds. In between the rows of Citrus establish ornamental peanut and low grass between the orchard rows. These strips will be mowed and could be used for ruminant feed with manure being used for your compost needs.  Using woody or strawy mulch will allow for good weed suppression and lower the soil temperature greatly reducing the decomposition rate between the plant in the row. . I am confident if this combination of practices provides a system that when implemented will be conducive to producing a conclusive increase in the soil organic matter. The modest increase of soil organic matte will have dramatic effect in your low organic matter condition.  I hope your will try this and design an experiment to show it potential and utility. Best Luck. P

Well responded Dr Paul. Our major limitation is to retain the carbon improvement in the soil as permanent pool of soil carbon, regardless of organic manures you use.