Dear Biswas Sir,

Please follow these links and pdf attachments for the answer to your queries.

1. http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3791

2. http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/epw9888

3. http://www.extension.umn.edu/garden/fruit-vegetable/nutrient-cycling-and-fertility/

4. http://extension.psu.edu/plants/nutrient-management/educational/soil-fertility/managing-phosphorus-for-crop-production

5. http://www.extension.umn.edu/agriculture/nutrient-management/potassium/potassium-for-crop-production/

6. http://www.extension.umn.edu/agriculture/nutrient-management/soil-and-plant-sampling/soil-cation-ratios/

Regards,

Dear Dr Biswas

Although your question is opt, i don't think optimum ratio could work in the present context. Soil heterogeneity in regard to macro as well as micro-nutrients has been developed due to wide range of intensive cropping practices. Only site specific nutrient management  (SSNM)  could serve the purpose. 

Dr Biswas very nice thinking on the issue. In a growing season , if  you work out the nutrients availability , you will find concentration of most of most of the nutrients varying hugely , depending upon the moisture  availability in soil ,  functional changes in microbial diversity , mineralogical behavior , transformation in carbon pool ..and so on..Hence , these nutrient ratios will also undergo changes ..? My next concern is , whether  such changes in nutrient ratios of soil take palce in response to crop nutrient demand ..? If so , how these nutrient ratios change at different growth stages?  Can few nutrient ratios act as  defining criteria for any germplasm/cultivar/variety.?

Drs. Arvind Singh and Anoop Kumar Srivastava ·have provided good replies. I think there are several factors to consider while talking about ratios of nutrient in soils for economical crop yields. I mean just application of nutrients to achieve certain nutrient ratios or concentration  has to be in relation to soil factor, crop factors, environment factors etc etc.

Dr.Biswas,is your concern for total nutrient ratios in soil,nutrient ratios in soil organic matter or nutrient ratios for availble nutrients in soils?Also there are ratios among applied fertilizer nutrients,say N:P:K or N:K and nutrient ratios in plant tissues  say N:K or N:S, Ca:B at a particular groth stage.

Dr Rao,

Thanks for your kind response. I really need to know (i) ratios of total nutrients in the soil and (ii) ratios of available nutrients in the soil. How they interfere with plants' uptake. 

Dr Biswas , Dr Ghafoor and other friends . Perhaps , it is more paramount to develop a kind of premise , how soil nutrient ratios dictate the nutrient ratios in index plant parts. it will be more pertinent to look at the nutrient ratios based on intensity factor than on quantity factor . As i said earlier , certain nutrient ratios may not change  when traced along the different growth stages.  Rest of my responses still hold to be responded. 

Dr.Biswas,it is a difficult proposition you have brought  in(but at the same time I appreciate your question).We know that soil C:N ratio is some what stabilized at around 10:1 -12:1 and microorganism's C:N ratio is 7:1(I can be corrected).It is difficult to work out C:P ,N:P,C:S and N:S ratios in soils including the inorganic component of nutrients.C:N,C:Pand C:S ratios can be worked out for stabililzed carbon/humic and fulvic  acid component.Those are reasonably stable in a given soil under a set of good agronomic practices.Total amounts of nutrients may indicate the nutrient reserves  in a soil but ratios may remain same but the absolute  quantities can come down under cropping without fertilization.As we discussed in this forum on earlier occasions,the particulate/active /microbiomass carbon commonly represented by labile carbon  is the mineralizable pool which provides nutrients to plants on mineralization.The C:N ratio of the labile pool is important.The C:N,C:P and C:S ratio of organic materials(manure,compost etc)added to soil are important from mineralization and immobilization point of view.Among them ,C:N ratio may have a dominant role.Plant- available soil nutrients are not extracted by a common extractant ,so, it is difficult to work out their ratios.Only one can ensure the adequancy or otherwise of the nutrients through soil testing.We have been advocating certain emperical ratios among the NPK,NP or NK fertilizer prescriptions for balanced nutrition.The N:K,N:S ratios  in plant indicate the adequancy of K or S in relation to N in plant nutrition.So these are somesort of plant  nutrient diagnostic tools or indicators.

Some good discussion is there on this question. There cannot be an ideal ratio of all the nutrients in a soil because numerous factors control availability and uptake. It is fact that intensive cropping has exhausted soils in many nutrients. The maintenance is very important.  

Dear Anoop and Rao, very informative reply.

Dr Biswas your question inspires me to add the following comments.

You may be well aware that it is not only the the kind of parent material, removal of nutrients by crops and the human nutrient addition that determine the nutrient availability status of  a soil.

Nutrient availability, especially in natural soils is determined by the biological activity.

Certain amount of nutrients will be always held up in the microbial mass, which may not come out in our ordinary analysis of plant available nutrients in soils. along with the mineralizers, the mineral solubilizing organisms in the soils also are responsible for nutrient availability to crops. 

Even when certain nutrients appears quite low in the soil, Mycorrhiza enable plants to catch those nutrients. Plant roots also vary differently in mineral solubilization through root exudates.

Moreover, there are nitrogen fixing organisms too to determine nitrogen availability.

Overall, without knowing the biological process in tauto, our interference in soils only destroys in natural potential to nurture plants/crops in soils.

Ignorant management only destroy soils. Instead, if we learn the biological process in its total complexity, we will be able to manage plant nutrition at the cheapest and most sustainable way in our cultivation practices.

The chemicalized agronomic frame of thinking (pedological thinking) should be changed into an ecological or edaphological thinking so that we become capable of managing soils and soil fertility in a quite different, complex and sustainable way!

Of course there is no short cut in this process, but it demands hard work of intensive, collaborative research of diverse specialists!

Dear Dr. Biswas

I’m not aware if any work has been done to stablish soil fertility standards based upon nutrient ratios yet. I believe that this is an extremely difficult task because different soil properties (including physical properties) may influence the bioavalability. Besides, nutrients may be present in the soil in different degrees of bioavailability.

On the other hand, leaf diagnosis is a very powerful tool to indicate the real availability of nutrients, because it represents the real nutrient uptake by the plants. In this regard, one very successful method for diagnosis (and identifying optimum soil conditions for plant nutrient supply as consequence) is DRIS (Diagnosis and Recommendation Integrated System) that is based on dual ratios of nutrient contents (N/P, N/K, P/K, N/Ca,….) and gives a much better overview of nutritional status of the crops.

Yes, I agree to Barros.

The best ratio betwen  in the soil is Ca/Mg/K is 6:3:1

Very praise worthy response from Dr Angel; appreciated. I understand that leaf diagnosis is very powerful and we are using this technique frequently. However, there are few references that excess soil available N impair almost all secondary and micro nutrient uptake by plants. Excess P induces Zn deficiency; excess Ca and Mg depress K uptake. Application of N and P improves K uptake etc etc. My question, once again, is what are those excess amounts in terms of ratios in the soil that act as antagonistic way or as synergistic way?

Site-Specific Nutrient Management optimizes the supply of soil nutrients over space and time to match crop requirements. It will not only increase crop productivity but also improves fertilizer use efficiency. Site-Specific Nutrient Management based nutrient compositions will work.

Dr.Biswas,as pointed out by Dr.Malhotra,We will have ratios among nutrients when we supply nutrient through fertilizers through soil test based site specific recommendations.Well decomposed manures ,composts etc can also have nutrients in desirable/near desirable ratios.Soil nutrient supply depends on mineralization of labile carbon,desorption from soil adsorption /exchange sites and dissolution of certain nutrient containing phases/compounds.So one can have ratios for nutrients in solution phase but they  will be rapidly changing with soil moisture regimes,temperature changes ,nutrient uptake by plants and microbes etc.If multinutrient /universal extractant is used for estimating soil available nutrients one can estimate certain ratios.But chemical extractants may not appropiately estimate the release of nutrients from organic phase through mineralization .Ratios based on humic acids in soil may give some information on organic nutrient dynamics especially for N but they may not be usefulr for routine nutrient management point of view.

Dr. Biswas, please do not go to a state of intensive theory and academics. Soil and Plant dynamics has to be kept in mind always. Further, soil is a heterogenous system never remains static. Similarly the plant as well, leave alone plant biodiversity etc. I suggest you to adopt a thumb rule i.e., evaluate the living phase of soil with respect to quantity and diversity of soil inhabited micro organisms. So long as the living phase is active and dynamic, you need not worry about crop performance so long as you care for environment and health of all living resources and not crazy and greedy driven for quick wealth.

Great answer Dr Reddy! People often forget that soil is a living system. 'Fertility' is the output of its natural balance of living organisms including microbes.

Unfortunately, the pedologists considers soil as a purely physico-chemical system and give least attention to its life.

Many often forget the great words of the 'father of soil science', the great V V Dokuchaev that 'soil is a living system, born with plants, grow with plants and remain stable under a stable vegetation'.

Therefore, whenever the natural vegetation is removed for cultivation, we should remember that we as intelligent and responsible managers of the earth, has also taken up the responsibility of what the stable vegetation has been doing to maintain its fertility! Agriculture is a culture and not just a temporary business!

Each generation need to hand over this fertile system to future generation as if he/she is only a trusty of  this common asset meant for the entire period of human life on the earth! We have initially taken it up from our first predecessor - may be the natural system, or the creative ancestral or learned humans, as the case may be, who knew how to maintain its fertility continuously! Even if we have received it in a very bad condition, as a creative species, by adding life to it we can convert it into a fertile system! This is a real challenge of the present day ecological science! Why not now? If not now when? If not we, who?

If we remember this important principle in agriculture, we can maintain the soil fertility as such with each crop, and soil will never become barren due to continuous cultivation.

Of course, the basic ecological principle of 'limit to growth' and 'limit to needs' should be observed in all ecological managements.

It is high time that we all students of soil science now turn to the ecological or edaphological management of soils; otherwise, we will remain as  'pick-pocketer' of future generation , who destroy the opportunity and the rights of future generation to survive on the earth!

Thank you Joseph for your appreciation, We have been brain washed for over a century and continue to be so. It is high time we wake up to realize our follies in farming before the Earth becomes store house of toxins further. Please check the contributions of Donald Lewis, an octogenarian struggling hard to create a living phase for soils right from 1950s. He deserves to be called as the Ideal Son of the Mother Earth.

Dr Reddy and Dr Rao,

I appreciate your comments in terms of soil microbes, ecology and about ignorance of some people who give emphasis on nutrients, soil chemistry or physics!! Unfortunately, I have found no pin-pointing response to my questions- what are the ratios of important nutrients, if not all, that we should try to maintain during crop cultivation. Being a student of soil microbiology, I know very little about this subject; I definitely agree with you that many of us ignore soil microbiology: soil health without them is not possible.

Dr.Biswas I appreciate your concern and interest but the ratios  alone can not solve the problem of  nutrient depletion, yield  decline and sustainability of agriculture and even nutrition of plants and microbes.Physical environment ( soil structure,aeration, water/moisture regimes and temperature) and biological conditions go hand in hand.Chemical factors and processes also decide the nutrient availability, supply and growth conditions for plants and microbes.So microbial life can not be studied independent of soil chemistry and physics.Of course, nutients are food for all life on planet earth,We  have to always emphasize nutrients,aeration, water and energy for both plants and microbes.We have to extend our laboratory microbiology to field conditions to call it soil microbiology and get wider acceptance of inoculants or biofertilizers.

Dr Biswas , it is a very perplexed question to suggest a suitable nutrient ratios  for cereal crops , especially about soil nutrient ratios.  First of all,  nutrient  ratios are so dynamic in nature that any static value will not hold valid for variety of growing conditions , since they are governed by a number of factor like any other nutrient availability.   However , i am enclosing some useful information form the Policy Paper  on Crop Response and Nutrient Ratios . Hope , colleagues will find it useful while reading . 

A NPK ratio of 4:2:1 (N:P2O5 :K2 O) is generally considered ideal and accepted for macro-level monitoring of consumption of plant nutrients for the country as a whole. However, it is difficult to trace the genesis of this NPK ratio.The data obtained from these on-farm trials showed that increase in yield and response to N was much more than that to P or K, and that the response to combined application of NPK was not positive or even additive. A close examination of these data also showed that in irrigated wheat the All India average increase in yield due to N, P and K fertilization was 3.7, 2.3 and 1.4 q/ha respectively, while in rice it was 3.0, 2.2 and 1.4 q/ha, respectively. This made fertilizer N very popular with the farmers. Probably some of these data playeda key role in deciding upon the NPK* ratio of 4:2:1. Two things were, however, overlooked. Firstly, the yield levels were between 1 to 2 t/ha and the native soil P and K could meet the crop requirements. Farmers also used to apply farmyard manure on their farms. Secondly, response to P and K was much more on red and lateritic soils than on other soils, suggesting the need for a different NPK ratio for different soils. Post-Green Revolution trials under the same scheme brought out that in rice response to P was as good as to N and in case of wheat, it was even etter than that to N. Response to K was much less than that to N or P.

The introduction of high yielding varieties of wheat in 1967-68 made P fertilization quite popular in Punjab, Haryana and Western U.P. Further, response to N was higher in presence of P and K. This all brought balanced NPK nutrition to the forefront and farmers were quite convinced of this. The data obtained from the All India long-term Fertilizer Experiments, however, showed that barring Ludhiana for wheat neither the recommended fertilizer dozes nor yield or profit maximizing doses had NPK (N:P2O5:K2O)* in 4:2:1 ratio. At Ludhiana in wheat both the yield and profit maximizing rates of NPK application were in 4:2:1 ratio. For rice at Bhubaneshwar having a laterite soil, the NPK ratio for yield or profit maximization ratio was 1.6:1:1 or 4:2.5:2.5. Similarly, for wheat at Ranchi having red soil the profit maximization ratio was 2:1.5:1 or 4:3:2. These data clearly showed the need for higher P and K application in red and lateritic soils.

There one important decision out so many decisions that Cell may be created at IASRI or NCAP to work out the optimum N : P2 O5: K2 O ratio in consultation with PDCSR, Modipuram, using the data on crop response to fertilizers from different sources (PDCSR, Crop Improvement Projects of ICAR, Soil Test Crop Response Correlation Project, Long term fertilizer experiments, state agricultural universities,  tate departments of agriculture, ICAR institutes). These ratios may be first worked  out for different crops in 126 NARP zones. Weighted (area basis) N : P2 O5 : K2O ratios may then be worked out for different NARP zones, states and finally for the country as a whole. This needs to be done at a regular interval.  

PDF is further enclosed for further reading 

Dr Anoop,

Thanks a lot for your comments and attachment. Appreciated. Excess application of gypsum or dolomite, as advocate some corners, along with other elements soil potential for optimum crop yield. Potash mining is widespread now a days than a decade ago. So, we need careful evaluation. Thanks everybody for participation.

Dear Biswas,

Thank you for your excellent question. Detail and well elaborated information have been given by a number of scientists.  But, in practice it seems a bit difficult to find or maintain the recommended nutrient rations in agricultural soils.  I think what is important here is that intensive cropping system is one of the main causes of soil fertility depletion and nutrient imbalances, particularly in the current fertilizer/improved crop variety production system. As we have discussed in the previous similar deliberations, the present approach, fertilizer/variety system, will not be sustainable in terms of yield and environmental protection unless holistic soil and crop management approaches are followed.

The discussion on this question remained highly motivated.

The optimum consentration depends on the balance between them not the concentration of single nutrients.for testing the balance between nutrients you must use DRIS- chart or methodology.

I agree with Mrs Bahar optimum balance between nutrient is more importance than nutrient concentration in the soil this balance depend on DRIS-chart for every crop,furthere more we should take in consideration soil microbiology and soil health.

Interpretation of plant analysis results are also important to identify deficiency of nutrients. The three major methods include critical values, sufficiency ranges and ratios. Most advisory services use sufficiency ranges for interpretation. Ratios and DRIS analysis are generally used as secondary and supportive evaluations.

 Critical values: Critical values have been defined as the concentration at which there is a 5-10% yield reduction. The use of critical values for practical interpretation has limited value. It is suitable to diagnose severe deficiencies and has little application in identifying hidden hunger. Symptoms are generally evident when nutrient concentrations decrease below the critical value. Critical values are important in establishing lower limits of sufficiency ranges.

Sufficiency ranges: Interpretation offers significant advantages over the use of critical values. First, hidden hunger in the transitional zone can be identified since the beginning of the sufficiency range is above the critical value. Sufficiency ranges upper limits that provide some indication of the concentration at which the element may be in excess.

 Ratios: The interpretation of plant analysis results involves the evaluation of two essential elements together recognizing the effect of one element on the other. For example, N: S ratio where the ideal N: S ratio for most crops is 10-15. As the N: S ratio approaches and exceeds 18, S is limiting in relation to N. N: S ratio can be high when N and S concentrations are in sufficiency ranges.

Dr. Reddy we respect your sentiments. Really we need to think and act for the health of mother earth.

Nice response from Getachew . Infact , when you trace the nutrient concentration across different growth stages , nutrient concentration gets diluted with simultaneous accumulation of carbon as result of photosynthesis. Or sometimes , concentration of some nutrients increases as we move from pre-flowering stage to crop maturity , while others decrease , so there  counter-effect of on enutreint over others . To avoid such kind of stoichiometric relation  between the nutrients , nutreint ratio was propose d. DRIS is one such concept which effectively utilises such nutrient ratio , instead of nutrient concentration alone.  For example , in most of the perennial fruits , there is an inverse relationship between nitrogen and potassium , since nitrogen fertilization increases the number of fruits , while potassium fertilization improves the fruit size , not the number . but , physiologically , both cannot move together . More number of fruits are associated with smaller fruit size , a common phenomenon in most of the perennial fruits. so , leaf N/K ratio of 2.2-2.6 was suggested , with leaf N exceeding 2.2% and leaf  K exceeding 0.70% . this leaf N/K ratio was even suggested different for different citrus growing regions in South Africa.   Likewise , we can cite an example of interaction between K , Ca and Mg , it is tricorner interaction , operational in soil as well as plant  .    So , Dr Biswas has a point  , but equally difficult to arrive at such optimum range of different nutrient ratios . It could be possible based on plant analyses , but surely difficult task based on soil nutrients .  

The right response was given by Getachew, but to add something here, on intensive farming the missed activity is that it is not exactly research based farming system. For example, on soil testing and variety based nutrient removal capacity of the crops to substitute the amount  removed the soil by organic fertilizers. On soils frequently farming activities were done the situation is to difficult to manage if not appropriately managed at the beginning of the farming activities. Before every activities,  we should undertake soil testing, and then amend it with organic matters. When we want to produce high yielding variety crops our fertilizer recommendation should be known to to add the exact amount to the soil. Unless, high amount of  nutrient is removed from the soil lonely. Thank U for nice question U raised!

The best ratio in soil in ppm N:P:K 4:1:1

in meq/100gr. Ca:Mg:K 6:3:1

 Dr.Angel Marcelo,Ca,Mg and K appear to be in exchangeable form.The per cent saturation on the exchange complex may be 60,30 and 10.For your soil and crop of interest the ratio may be O.K.But for N,P aK how you worked out ratio? are they water soluble forms,extractable forms using an extractant (different extractants) or total nutrients?

I believe, total nutrients will give good indication because they would be available for plant's uptake under favorable conditions.

Dr Rao. N , P e K are availables under favorables conditions 

A very lively discussion and excellent answer from Anoop, showing the close relationship of  nutrition of plants and their physiological responses. So back to the question, in order to address the change of nutrient balances due to crop intensification, the soil management system to be followed will have a big impact in terms of soil quality, agricultural productivity and  sustainability. The discussion needs to be beyond the fertilizer and seed system to maintain crop yield, ignoring the soil system (the resource base).    

Very good answer from Anoop. The use of DRIS on concept of nutritional balance of a plant is becoming an efficient method to assess the nutritional status of plants, this method puts the limitation of nutrients in order of plant demand, enabling the nutritional balance between the nutrient in leaf sample.

Sorry to side track the topic and its objective just to broaden the discussion on plant response and behaviour. It is reported extensively that plants respond to magnetism and music (of course melodious music). Does it mean these modify their nutrient absorption and growth? If so, our knowledge on plant behaviour with reference to nutrient supply from soils becomes complex if not confused due to magnetic and music interventions. In this context, contributions from Dr. J.C.Bose,the noblest son of India deserve to be recalled as he demonstrated plants to possess the power of expression not realized nor propagated later to this day. Therefore, it is time for us to stop shadow boxing and start caring plants with intensity and concern and not to view them as mere instruments of elimination of human hunger..   

Dear colleagues, I request you to look into the following reviw article on DRIS available online.I shall give first two lines from conclusions and provide the reference.

'A careful overview on the scientific literature reveals that DRIS is a promising ,effective auxillary tool for diagnosis in several crops,although,still unknown,barely studied and applied'.( My own comment,can somebody give real success stories with DRIS on large scale in any country).

DRIS:concepts and applications on nutritional diagnosis in fruit crops. by Francisco de Assis Alves Mourao Filho  Sci.Agric.(Piracicaba,Braz.) vol 61,no.5 Piracicaba Sept-Oct.2004

http://www.scielo.br/scielo.php?sci_arttext&pid=S0103-90162004000500015#

The uploaded articles seem interesting.

Dr Anoop has Because of intensive cropping, soil nutrient compositions are changing. yes this is one reason and another is imbalance utilization of fertilizer is also a major cause of soil nutrient composition changing. The composition of soil varies according to the parent material, but by balance fertilization we can preserve the diminishing nutrient content from soil.    

Often, the term 'Balanced Fertilization' is used extensively by the fertilizer firms. Even for scientists it has become a catch word. But what is meant by this term? Is it precisely defined to mean something scientific and truthful? If so, complex fertilizers NPK are manufactured in different ratios such as 19-19-19, 28-28-0 etc. Are these NPK ratios reflect balanced supply of nutrients to crops? Do the crops absorb NPK in the same ratio as these complex fertilizers supply? If not, where lies the so called balance? Fact is, farmers are driven to purchase them irrespective of crop requirements for NPK or whatever. Scientists play a second fiddle to the tunes of chemical industries as there is no option and farmers are ultimately the sacrificial goats in this process who are debt trapped driving them to suicides.  I know I have side tracked the topic. But let there be honesty to help farmers to live in dignity and honour. Many opt to work as labour than to farm their own lands. 

 Dr.Srinivasa Reddy,If I am sure,you might have taught students the  importance of balanced nutrition and balanced fertilization concepts.Governments in many countries are promoting balanced nutrition,balanced fertilization for optizing crop production,to avoid nutrient depletion and excess accumulation in soil, water,air or environment.Though the complex fertilizers may not exactly provide balanced nutrition to every crop,they help to attain the goal of balanced fertilization if nutrient doses properly calculated and applied.Some supplementation can be made using straight fertilizers to arrive at right doses for a particular crop.As you are aware crops are many and complex fertilizer forulations are limited .Also, the requirement will change with crop yield and soil test(to say simply).If complex fertilizers are miss used the farmers need to be educated in proper use of fertilizers.We also know that balanced nutrition can better be achieved through combined use of fertilizers and manures.There is a INM division in the Ministry of Agriculture and Cooperation and the ministry is promoting balanced fertilization, INM ,soil testing and soil heaith in the last 15-20 years .The following publication give some history, concetpual  development and definition and the purpose it serves.

Balanced fertilization and regulating nutrient losses from agriculture by Oenema,O. and Velthof,G.L.

hydrologie.org/redbooks/a273/iahs_273_077.pdf  Available online.

Dr. Annangi Subba Rao has added a logical explanation to the question and others have also contributed significantly. But we have to keep in mind the small illiterate farmers. These farmers or persons are keeping themselves engaged in agriculture since they could not undertake any other activity for their living. My point of interest/ concern is awareness among such farmers regarding the multi-nutrient/ complex fertilizers and then balancing the nutrients as per crop requirement for any designed yield level from particular soil. 

Dr Gaurav Singh , i am in total agreement with you . Despite many efforts  predominantly relating soil test -based recommendation for  balanced fertilization , nutrient mining is more or less a common phenomenon , with exception of phosphorus buildup at some places in southern penninsular India.  Dr Ghafoor has flagged a good point that look at the small farmers  who have every little knowledge or access to such techniques of balanced fertilization . The only option left is to keep vigil on the crop performance  seasonwise and keep farmers sensitized about the deteriorating nutrient pool of soil vis-a-vis lower crop yield. Sometimes , simple addition of organic manures/composts also do world of good to  keep  soil in fertile mode. 

I humbly stand by a singular question i.e., When the NPK ratio of a complex fertilizer is say 19-19-19, does it mean that a given crop grown by the farmer absorbs NPK in that ratio? Are the scientists not familiar by their own research and theoretical knowledge that N is absorbed to a greater extent by quantity than the P? That is K stands next to N and least is P as for NPK are concerned. Where is the balanced nutrient supply here when equal quantities of NPK are found in this complex fertilizer? How do you expect poor and illiterate farmers to calculate the quantity of NPK required by a given crop and apply, so much so the scientists themselves start asking questions in ResearchGate as how to quantity NPK application whether on area or volume basis? 

In the last two years I have been more interacting with farmers,scientists and fertilizer industry more in field situations compared to my earlier research and research  management positions.As mentioned by me earlier,though the complex fertilizers are not made with a sole purpose of meeting a particular crop,they  have become favorite fertilizers in a particular crop in a particular area.Say NPK14-35-14 found favour with groungnut farmers.28-28 is preferred by rice(maize) farmers in South India.19-19-19 is water- soluble fertilizer.17-17-17 is also used for basal dressing in rice.Mostly P and K needs are met by complex fertilizers and N can be topdressed.If we take any crop, the crop removal of K is much higher than K applied through complex fertilizers or straight fertilizers.So unnecessary K accumulation may not be a problem and K fertility deterioration of soil can be arrested to some extent.There is no scope for N accumulation when complex fertilizers are applied as the uptake of N will be more than the N applied through complexes.Only posibility is P accumulation ,when more than required amount P fertilizer is added.This is possible only when NP or NPK complex fertilizers are used for topdressing in place of urea or muriate of potah in crops like rice.This issue was thoroughly discussed in the researchgate forum when I raised the question on this aspect.Creating awreness among farmers is job of scientists, Government and Agricultural university extension agencies etc.In fact our fertilizer and manure recommendations need refinement in view of much higher yields/near potential yield harvested by farmers in crops like rice and maize and lower amounts of nutrients recommended for those crops.Nutrient balance sheets needs to be worked out in important/ dominant cropping systems to avoid soil nutrient depletion , for sustaining higher yield and maintaining soil health

Dr. Rao's point is valid.

Very pertinent response from Dr. Anoop and Dr. Rao. 

Holistic and balanced reply from Dr.Rao from the stand point of fertilizer industry and bureaucrat/ agricultural scientist/extension officer. With this understanding and practices, living phase of soil if not already extinct, becomes a casualty due to which health and quality of living resources has been deteriorated. It is nothing but chemical industry driven farming practices. How come there is shortage of pulses right now in India despite the use of these chemical fertilizers, pesticides and herbicides, eventually resulted in import of pulses from abroad? What is the fate of soils of Punjab, the State of five rivers? We echo at the top of our voice on climate change and global warming worldwide and adopt 'I mess up and you clean up' principle directed towards under developed world nations to combat climate change and global warming.

Dr Agegnehu, Anoop and Reddy,

I appreciate your comments. The use of sub-optimal fertilizer rate and use in excess amounts are the bottlenecks of sustainable crop production. Moreover, we generally ignore soil microbes in many cases along with industrial pollution. We are responsible for changing soil store house.

Dr Biswas, apart from, what  you said , i feel perhaps , most important is, the  distinct absence of  monitoring and evaluation criteria of soil fertility evaluation / nutrient mining  with respect to specific crop /cropping sequence in a given farming system mode . If at all , we have such criteria , we  have failed to replicate the same ease of success under  other cropping situation ..?

Sooner or later , microbial load of soil has to be introduced as one of the criteria  for  soil fertility evaluation ,besides conventional parameters used . In this context , comments of Dr Biswas are valid.  

I am extremely and forever grateful to 'ResearchGate' for having caused global coordination, understanding and unity in diversity among scientists and others to set a positive direction for improvement and sustenance of the planet Earth and in turn the quality life of all. Thank you Dr Biswas, Dr A K Srivastava, Dr Agegnehu.

I totally agree to Dr. Kumar's point that we are exhausting soils so rapidly with increasing crop intensity and obtaining high yields which warrants sustained soil monitoring system and subsequent replenishment.

Sustainability of intensive cropping systems can be maintained only through application of both organic and fertilizer sources of nutrients to meet crop requirements at different growth stages. Location/site-specific nutrient management for different crops is the way forward, but addition all available organic materials is critical to maintain soil organic matter level which supplies most of the micronutrients through microbial activity. Plant and soil based methods are available for monitoring the soil nutrient status for continuous production.

Dr.Balasubramaniam,your three sentences answers many issues raised by colleagues including me.Integration of all  available( safe)  resouces,their efficient management and monitoring  soil-plant-animal/human system are really crucial for sustainable agriculture.

I agree with the facts that nutrients depletion is a major issue especially where intensive cropping systems are practised. An integrated approach of nutrients management should be the solution. Balancing soil organic matter should be given the prime importance. Available nutrients through various  sources should be integrated such that nutrients are balanced for the targeted yield goal, soil fertility is improved (at least not declined) and soil organic matter is balanced.  

Let us feed the soil not the crops. Adoption of suitable crop rotation and organic farming practices will solve all the nutrients related soil problems.

With the folowing equation we can obtein the adequate dosis of nutrient (DN)

DN= (Q ABs./Ef) - Q soil.

Qabs. = Quantiiti recovery for the crop

Ef= Eficiency of nutrien

Qsoil= Available nutrient in the soil.

Then exist diferent ratios for diferent crops.

Dr.Angel Marcelo,your formula is is interesting.But one can not directly deduct the soil available nutrient ,Qsoil from the QABS/Ef.But it has certain similarity to our STCR targetted yield approach.We have three components in equation.1.Nutrient requirement by the crop(NR) in kg nutrient/tonne grain=Xf/GY.

 Xf=Nutient in grain plus straw of fertilized treatment.GY=grain yield in tonnes

2.Contribution from soil available pool(CS).This is obtained from soil test value(STVo) and nutrient uptake from grain plus straw in control(unfertilized)treatment (Xo) .  CS=Xo/STVo   

3.Contribution from fertilizer (CF)is obtained  by deducting the uptake of soil nutrient from the nutrient uptake in treated  one(Xf)

CF=[Xf-(STVf x CS)]/ Af      Af=amount of fertilizer applied;STVf=soil test value in fertilized treated plot.STVf xCS gives the soil contribution of nutient in fertilized treated plot.

Fertilizer dose(kg/ha)=(NR x T)-(CS xSTV)/CF  T is yield target.

it is ok

All those traditional calculations is based on the concept that soil is just a dead medium of plant growth. Soil amendments that do not take into account the biological process of nutritional supply to crops is the ultimate reason for soil degradation, other associated environment degradation as well as poisoned food products!

Shrinking land area per capita and declining soil quality have led to a sustained increase in the rate of inorganic fertilizer application from year to year to enhance or maintain agricultural productivity, where this is an option. Allocating more land to agriculture will not offset the negative environmental impacts of land degradation in the future, instead a more promising approach to ensuring food security is to enhance yield from currently cultivated land where productivity is low.

Thus sustainable agricultural intensification, increasing productivity per unit land area, is necessary to secure food supply for the increasing world population. But inorganic fertilizer application alone will not be a sustainable solution to improve soil fertility, maintain nutrient balances and yield increases. Rather application of excessive inorganic fertilizer, especially N, may cause soil deterioration and other environmental problems due to more rapid organic matter mineralization. So integrated soil fertility and plant nutrient management approach that incorporates judicious use of organic and inorganic nutrient sources as well as appropriate cropping systems with inclusion of legumes will maintain soil nutrient balance and sustainable yield

Dr.Agegnehu,I fully endorse your view.Dr.Ramamoorty's targeted yield approach incorporates the contribution of soil, inorganic fertilizers ,organic manures and biofertilizers.There is also provision in the approach to fertilize the crops on cropping system basis using the post harvest soil test value prediction equations.Full details of this approach and methodologies are available in the following publication.

Ramamoorthy,B and Velayutham, M. 2011.The"Law of optium" and soil test based fertilizer use for targeted yield of crops and soil fertility management for sustainable agriculture.Madas Agric.J.,98(10-12),295-307.

Dr. Rao and other discussants, as you know the land holding per individual farmer or household has been consistently decreasing because of population growth, expansion of cities and industrial places, increasing demand for food and raw materials including bio-fuel crops. As a result, the scramble for agricultural land has been intensified globally. So intensification is the solution to fulfill these demands.

I think this discussion can be viewed beyond soil nutrient deficiencies and balances, because intensification is not only increasing farm output per unit of land using external inputs. To maintain soil quality and yield other components of of intensification need to be considered. For example, multiple cropping systems.  Can you say  something in this regard as multiple cropping is a common practice in Asia?

Cropping intensity is about 200 in Bangladesh.

Dr Getachew , i endorse your opinions . Despite competing land uses , cropping intensification is one of the effective ways of fulfilling the food demand and supply chain with shrinking agricultural  lands. Under such circumstances , soil health -soil ecology plus environment , how do we address these issues..? Do we have any prediction models , like in good olden days , we use to develop crop agronomic models , they  were so effective and so comprehensive , but now they have become irrelevant , why...?. We surely need to look at better evaluation and monitoring system under such changed scenario. 

Dr. Anoop you raised very pertinent points that may invite more discussions and further studies in relation to optimizing cropping intensification.

This is again a very good point , do we need to optimise the cropping intensity as land capability classification ( We need further fine tuning of land quality and other associated properties in relation to sequence of crops to be grown ) , or keep expending then  cropping intensity considering the pressure of demand , what about the carrying capacity of a given  soil  ...?

Some of the basic researches are neglected in developing countries because of economic constraints and mentality of our supervisors. For example, in 1985 I joined BRRI as a researcher. I used to hear from the seniors that no basic research is needed. We can use the knowledge of developed countries. Now-a-day it is realized that we need basic research to solve our problems. Carrying capacity has already been depleted, if not totally, in many places. We need to find out hidden hunger, process response to relate with agronomic models for prediction.

Nice comments from Biswass. You indicated the cropping intensity at Bangladesh 200%. How could the intensity be doubled? Can you mention the major highlights of the practice? For example, cropping pattern, irrigation practice, crop diversification, etc. 

Most important of all , is the carrying capacity of soil . And , with 200% cropping intensity , will put  an extra load on the carrying capacity of any soil  , resultantly , soil will not be able to sustain that  cropping intensity for so long to be really remunerative in terms of benefit -cost ratio or production economics. Dr Getachew is right ....

I agree with the very important queries raised by Dr. Annop. So what are the possible alternatives in areas where an intensification with this extent or more is necessary to satisfy food production?

This is where , we need a kind of budgeting ,  an appraisal of off- site movement of different inputs in form different drivers of sustainability . There is a term called , crop sustainability index( CSI) , we need to work out to really declare a cropping sequence sustainable or not ..eventually need lot of exercise at regional level to fine tune such CSI.