Suggested to apply 25 or 50 % of recommended dose of fertilizer. Because, to sustain the high values for consecutive crop other wise all the NPK and OC will be depleted.

 When we consider the approach/method of applying fertilizers based on low ,medium and high categories,the  general recommendation is  for medium fertility category.When the soil test values are low, we will increase the recommendation by 25-30% over the general recommendation .Similarly, when the soil test values are high ,we decrease the recommended amounts of nutrients by 25-30% over the general recommendations.

 When we consider the approach/method of applying fertilizers based on low ,medium and high categories,the  general recommendation is  for medium fertility category.When the soil test values are low, we will increase the recommendation by 25-30% over the general recommendation .Similarly, when the soil test values are high ,we decrease the recommended amounts of nutrients by 25-30% over the general recommendations.

certainly not, as long as you are confident in the calibration of your soil test!

If the soil test values are high,we reduce the amounts  N,P and K generally recommended for a particular crop by 25-30% and apply.

There are two different schools of thought:

1. One group of researchers says, apply 25% of the recommended dose.

2. Another group says that there will be no response of the applied fertilizer because soil values are high. This will unnecessarily  increase the cost of cultivation.

Question is that what we have to recommend to farmers? I think in this platform we can find out the right answer.

Regards

Generally, I agree with previous answers, especially regarding P and K (reduced doses by 50-80%). What is interesting, Irish recommend to NOT APPLY such fertilizers on soils rich in both nutrients as it was suggested by Prof. Schnug. However, the Irish soils seem to be very fertile, climate is very favourable and they have a lot of animal manures, due to the fact, that 70% of  their agricultural land are grasslands.

When speaking about N, I think that the content of N-available is very labile and strongly dependent on weather conditions. For this reason, I would recommend to adjust N-fertilizer dose on crop requirements (expected yields) with only small modifications depending on results of soil analyses. Moreover, I would modify N-doses even to the history of weather in last weeks. For example, if there were no rain, I would not apply N, because soil still remain with N- applied before and in such case water is a limiting factor, contrary to N and other nutrients. If it rained a lot, I would apply relatively great dose of N, because the N applied before could be leached - in such situation it is rather N a limiting factor, and not water deficiency.

 Dr.Schnug,from around 1956 on wards ,in India  several state soil testing laboratories are following the low,medium and high categories of  soil fertility in  respect of N,P and K and recommending fertilizers as per details given by me in my earlier reply.From 1996 on wards we have been advocating targeted yield approach where we have prescriptions or calibration tables for different crops on diverse soils of India.In this approach we recommend fertilizers based on yield target and individual soil test values.We can generate recommendation to each soil test value irrespective of nutrient.How ever when soil test values are too high or too low we recommend certain minimum dose to avoid unnecessary depletion soil fertility and consequent yield reduction.For all important crops of India  in different states the recommendations are available in website of Indian Institute of Soil Science,Bhopal under STCR project

http://www.iiss.mp.nic.in

Recommendation of fertilizer use should not be based on only soil test value but also on the nature, growth duration, yield level and nutrient demand of the crops to be grown. From the soil test value, one can compute total nutrient content available in the soil. Then from the estimated nutrient requirement of the crop (considering its growth duration and production level) to be grown by the farmer, one can make more meaningful recommendation on the use of fertilizers.         

 I am in agreement with What Dr.Subba Rao, Ex-Director IISS Bhopal has suggested. Reduce fertilizer dose by 30% as long as NPK status showed high value. You can suggest to apply FYM in INM mode keeping view of equilibrium status of SOC in the that areas (soils).

there will be no response of the applied fertilizer because soil values are high. This will unnecessarily increase the cost of cultivation.

Dr.Kundu,the targeted yield approach /methodology involves  crop yield level ,nutrient uptake and soil test values in the computation of fertilizer nutrients requirement for a particular crop.Please go through the following review paper  for further information.

Soil Testing and Nutrient Recommendations A.Subba Rao and others Journal of the  Indian Society of Soil Science ,Vol 57,No.4,pp 559-571 (2009)

 Dr. Jeet Singh your apprehension is right but not practically valid.Except for some short duration legumes,fertilizer nitrogen has to be applied to crops for their optimum yield.More than 90 percent of Indian soils are deficient in available N.It is not easy to build and maintain high  N status in agricultural soils.In case of potassium the recommended K levels hardly meet the K requirement of crop/crops(when uptake of K is 80 to 150 kg /ha level we recommend  20-40 kg K2O/ha).The added K may to some extent arrest the K depletion.However in case of P there may be some build up overs .There are three options for high P soils,(1)skip the P application for two to three crops and then test soils for P status to take further decision,(2)apply at least 70-75% of recommended level and the third options is replace P through fertilizer  equivalent to crop removal of P.So among the three, the second option is practical from farmer point of view.If have adequate P in soil try to establish through research the replacement values(fertilizer requirement) equal to P uptake for different crops on diverse soils.

Ideally the amounts of fertilizer can be adjusted based on soil test results.

In many of US states experimental state University recommendations are categorized into low medium and high soil levels. Based on the soil test levels the fertilizer targets are adjusted accordingly.

Another important factor is that different crop species and varieties can act very differently. With a variable responsiveness rates can be tailored to them.

When using a crop like maize the tissue assay at 15 cm height can be used to pinpoint lay by fertilizer N at cultivation.

In terms of Organic Carbon usually about 2.5% or about 5.0% soil organic matter the emphasis on building a higher level is not high priority.

The consciousness of not wanting over application is very astute in relation to cost and environmental issues which can be associated with nutrient additions.

Hope you were able to use some of this information for your benefit.

I agree with all the answer. The different plants have the different responses to fertilization when the nutrients contents are high in soil. I think it would be best to give the 60% of recommendations values for fertilizer application.

In India, Agriculture department and SAU of different States framed out fertilizer recommendation for different crops based on soil test values. Some states categorised soil test values in very low, low, medium, high, very high etc. and some states in low, medium and high.  Some states follow ICAR norms. As per this rating they have adjusted dose of fertilizer to get maximum yield. Naturally,  low soil test values means high fertilizer demand and vice versa. Targeted yield concept is more scientific approach for scheduling fertilizer in different crops. But this need adequate research data for each crop in each soil type and also in different agrocilmatic condition. So, in India high soil test values does not imply that threre is no need of fertilizer. 

Dr.Hepperly,I appreciate your comments.But in tropical countries like India our soils can not reach the level of 2.5% organic carbon.We have ratings of low ,medium and high corresponding to 0.75% organic carbon.Only in Vertisols or swell-shrink or heavy black soils we have organic carbon in the range of 0.5% to 0.75%.In all other soils the carbon content may vary from 0.2 to 0.6%.In rice soils(heavy textured),forest soils,Mollisols  etc.we come across organic carbon nearer to 1.0 % or more.

Dear Dr. Hepperly and Dr. Rao. I think there is no contradiction between you! Also in Poland (moderate climate) it is very difficult to obtain 5%of organic matter (we can recalculate it into organic carbon) in soil, may be because of the fact, that we have about 40% of sandy soils (poor or no formation of organo-mineral complexes).

Moreover, according to my observation from recent 4 years, if mineral soil contains about 5% or more of organic matter, it has most frequently drainage problems!

Additionally, we have very good wheat production on soil with much smaller organic matter content (1-1.5%).

Consequently, as Dr Hepperly wrote- there is no priority to obtain such high levels of organic matter. However, it would be very difficult as Dr Rao wrote. But - not only in tropical climate, but, in my opinion in majority of soils with proper water-air relationships.

Dr.Michal, I appreciate for good information shared.

Tell me at which area your soil testing values are high. You being a scientist analyzed the soils or some one else.  If it is Hill soils,  you need to apply fertilizers for optimum yield. Plains and valleys surrounding your Institute are already deficient in major nutrients. You need to see crops, cropping systems etc on ground level for advocating fertilizers. Doing something in lab doesn't have much applications in farmers fields. 

Dear Dr. B.S. Mahapatra

Thank you sir for your answer and concern. I being a scientist analyzed samples by myself and found the results are moreover same in the range of samples which were analyzed by our soil lab experts. These soil samples belong to mid hill areas of Dehradun and Uttarkashi  districts of Uttarakhand. These are hill soils abd major nutrients are available in the high range. 

My very simple query is that whether we should recommend fertilizer to these soils or not? If yes, then how much of RDF? 

To view the farmer's economics , there will be no response to these 25 or 50% RDF because soil values are already high. 

As I could draw a conclusion, when these soil values will fall in the category of 'medium' from high values, then only we should start recommending the fertilizer to farmers. Up to that level, farmers are already applying some extent of compost, FYM, forest litter etc. to their soils. Am I right sir?

Can you please give some details of data generated  including number of samples ,no of samples in low ,medium and high categories?  The crops grown in that area and manure and fertilizers being applied by them based on some survey to get better idea of the area and get proper advice from colleagues.

Can you please give some details of data generated  including number of samples ,no of samples in low ,medium and high categories?  The crops grown in that area and manure and fertilizers being applied by them based on some survey to get better idea of the area and get proper advice from colleagues.

Dr Singh , first thing , you have to do is to ensure that your soil test values are really going towards higher side . The suitability of soil test values in terms of application to that soil , crop , growing conditions etc ,  is another very important issue , we have to look at . And most importantly , such  soil test values are so dynamic  in nature , that you fix the target yield at higher level , these soil test values will become optimum or sub-optimum values , so recommendation of fertilizers is lot dependent on the soil test -crop response -based calibration models. I  do not know  , what kind of procedure , you have adopted to arrive at such conclusion .

How are we missing the information on micronutrients?. We need atleast annual maintenance dose  of micronutrients or corrective doses depending upon the diagnosis. Your any recommendation based on NPK will be a failure if such recommendations are not accompanied by recommendation on micronutrients.  

Dear Srivastava,

If really high, curtail the NPK fertilizer accordingly based on crop NPK use efficiecy of that particular crop by providing half of the required dose for the 1st year and subsequently to 1/4th dose until the soil test values for NPK  comes to the normal level by taking care of micro nutrients. 

Binod , soil test value rating has to be on the basis of target yield  for annual or perennial crop. And the limits of low , optimum and high are , if based on yield response , how would you then decide these limits of low , medium and high . Means , if soil test value is optimum for any  nutrient and for a certain  yield level ; you raise that yield level , do you feel that soil test value will still be optimum , my answer is straight no , it will be suboptimum. Now , the next question comes , if your  soil test value is optimum at certain yield level , let add some maintenance  dose of  nutrients ,  applicable only in perennial crops. but in perennial crops   , I agree you can forgo till your soil test value depicts certain deficit level.

Considering these limitations of conventional soil test-crop response relations, we need calibration models using tripartite relation  using soil test values, yield levels and dose of fertilizers. Such an attempt will straightway ward off such discrepancies  in fertilizer recommendations . and one fourth , half , three fourth reduction or increase in fertilizer doses based on soil tests  , I feel  has no scientific basis. We need to calibrate such relations for given soil type in a given cropping system / farming system

Srivastava, in general there is limits for the soil test value viz.- low, optimum and high whether, it is kharif/rabi crops or annual or perennial crops or tree hence, depending on the production/productivity of any crop/annual or perennial crops, the fertilizer doses are quantified(target yield and genetic potential). So, that after consuming, the level of  soil test value limits may remain  optimum otherwise, low (control) hence, to maintain the soil fertility and productivity, fertilizer dose should be applied/fixed on the basis of factor production or yield response. 

Further, calibrating models using three ways will also results in a same way hence, for reaching the goal/objective we are using different boat.

whether, regression(polynomial) or path analysis or regressotree, the matter remain  alike.

 Dr.Vinod Kumar,I appreciate your reply.The fertilizer recommendations to field crops(not horticultural)have evolved over time with available means with the researchers .Initially general fertilizer recommendations were arrived at using quadratic response function in different states on diverse soils based on the data generated in Model Agronomic trails.These fertilizer recommendations were for medium fertility of soils. Subsequently the soil testing laboratories were established and limited soil fertility data was generated.With limited data in a vast country like India,they have not enough data to give recommendations soil wise.But they grouped the fertility data into low, medium and high and decided to recommend 25-30%more in low nutrient status soils and 25-30%less in high in high nutrient soils.I remember that some verification trails were conducted in areas adjoining Delhi.I do not know similar excise was done in other states or not.As some variations were there in fertility categories and recommendations in different states probably they might have done some varification trails. Subsequently the Soil Test Crop Response Correlation project was initiated in 1967-68.The project used both targeted yield and  multiple regression approaches involving soil and fertilizer nutrients.But we find difficulties with multiple regression approach and currently recommended fertilizers,manures or bio fertilizers(limited information) are based on targeted yield approach.Some STCR centers have done good innovative work with different response /regression models like quadratic,quadratic plateau,linear plateau etc.But the recommendations generated are not sufficient to recommend fertilizers in different states.For soil fertility maps and targeted yield based recommendations,one can visit IISS website.Now many states have their recommendations on their University websites or software form.

Binod , I request you to please have a visit the question  entitled  How effective is recommended doses of fertilizers  on ResearchGate where respondents were overwhelming and the it was a huge discussion . I hope , you will love to see the real  quality discussion. I would only say,  there is a world of difference ,   the way fertilizers are recommended in annual crops vis-à-vis perennial crops.  

We can not determine any recommendation for them if we only have a soil test value of OC and NPK. We need more data of soil type, soil texture, drainage, pH (acidity), season (climate considering to water availability/supply), crop/commodity, planting period (considering to climate factors), target of yield/productivity, etc.

Better if we observe from the indicator vegetation/indicator plant that grow on the plantation area for more accurate of fertilizer recommendation.

We should responsible for any scientific theory/recommendation we have stated to them (farmer), so, be wise and study any case by considering any factor concerned.

Thank you, salute for India with a lot of agriculture experts...

 Mr.Wahyu,good points raised.Normally separate recommendations are available for irrigated and rainfed crops.Also, the recommendations are different for Kharif(rainy season,June-October) and rabi(Winter, November to March).For some crops like rice ,there are separate recommendations for short duration and long duration crops.Now targeted yield based recommendations are available for different crops on different soils.So most of the points raised by are covered.We have work further to improve/refine the calibration system for taking care of  some points raised by you like drainage and weather fluctuations( resilient crop varieties are more important).

Wahyu , I agree with you  about these concerns .You develop a preliminary calibration system , and gradually go on adding such variable , keep on readjusting the procedure of fertilizer recommendation , eventually arriving at such a robust calibration system which could accommodate these variables. Unfortunately  no such  models as of now exist.  Nutrient Experts developed by IPNI  using crops like wheat , maize etc have shown some  initial promise . Lastly , farmers need straight soil test-based recommendations,  capable of giving them the profits in terms of additional yield , without any nutrient mining  or any other soil health-related issues in their fields.  

when the organic carbon and NPK values of your soil is high.if the sampling method is accurate and there were no errors during chemical analysis.There is no need for fertilizer addition so as to avoid what is called luxury consumption.Basically check your your sampling  methods,analytical and calibration methods to ascertain accuracy..The extent of P- fixation in the soils determine,to a large extent, the P-fertilization requirement for optimum crop performance.The interpretation of the available P-values in terms of fertilization requirements,in the face of critical plant requirements,may require a knowledge of quantity/intensity relationship i.e P-buffering capacity or fixing capacity of the soils,Finally NPK applications depend on crop cultivars, soil types and their requirements

when the organic carbon and NPK values of your soil is high.if the sampling method is accurate and there were no errors during chemical analysis.There is no need for fertilizer addition so as to avoid what is called luxury consumption.Basically check your your sampling  methods,analytical and calibration methods to ascertain accuracy..The extent of P- fixation in the soils determine,to a large extent, the P-fertilization requirement for optimum crop performance.The interpretation of the available P-values in terms of fertilization requirements,in the face of critical plant requirements,may require a knowledge of quantity/intensity relationship i.e P-buffering capacity or fixing capacity of the soils,Finally NPK applications depend on crop cultivars, soil types and their requirements

Dr Olubunmi , to me , rating soil test value with respect to a nutrient , and for a specific crop  in a given agro-pedological set is a huge effort , without any generalization . Probably , we need this exercise more rigorously to be persued before going for a soil test interpretation and  fertilizer recommendation . And this is where we repeatedly fail in utilizing the soil test results.   

A fertilizer recommendation will depend on the soil test, the crop or crops involved and consideration of ability to pay and get a return on investment.

For example almost never would it pay or be useful to fertilize a legume with Nitrogen when biological nitrogen is plentiful and when Rhizobia inoculation would be available.

Many soil factors show a law of diminishing returns so heavy applications can be counter productive. Most response to soil organic matter comes from increasing from 1 to 5% soil organic matter after that point the increases may be counter productive. Ergo the soil analysis is critical.

The more complete the soil analysis the better but even that is not even we need to confirm and evolve our treatment by taking a look at foliar nutrition levels. This to needs to be complete look not just the macro nutrients.

The literature for your crop(s) needs to be explored and the target levels for your fields defined.

You may not have all these tools readily available now but this area of expertise is rapidly evolving and farming communities can work together to get the experience and knowledge they need. Ideally scientific and traditional practices can be used apart and together to get the best of all approaches.

Some thoughts. If your P1 test is over 30 you definitely could reduce your emphasis on it if is under 10 I would continue to focus on optimizing. In terms of K you will not optimize your system until K level is 300. Lidewise if Calcium is less than 1000 think about increasing and Magnesium under 100 there is a problem.

Practically all nutrition for the majority of plants is optimized at pH 6 to 7.3 if you are lower or higher than those levels you can improve your results through modifying pH either liming for acidity especially if under 5.7 and sulfuring or ammonium sulfate for pH over 7.3 especially if over 7.7.

I stress micronutrients because much remediation can be achieved by low input in India some people have shown up to about 50% of the crop soils can be Zinc deficient and just a few Kilograms per hectare can remedy these situation and can be targeted by soil, seed and foliar.

Good points Paul you raised . Many  a times,  buffering your soil pH around workable range may not be possible. Yes , the emergence of micronutrient deficiencies in scale and distribution , are the major cause of concern , though ,  required in few kg on a ha of  field , but leaves a strong masking effect on the functioning of macronutrients, thereby , checks the magnitude of response of fertilization,  if not based on sound soil test -based interpretation  and follow up..

Soil tests for N ( available N or soil organic C) hardly carry any meaning and should not not be used blindly to recommend fertilizer N to different crops.  A close examination of leaf colour for crops like rice, wheat and maize can be very helpful in deciding how much N should be applied.  Decisions can be made when the crop is already growing because leaf colour takes care of N supply to the crop from all sources such as fertilizer, manures, irrigation water, rain, residual effects of previous N applications, nature of the soil - - and anything else....Use of leaf colour chart can be very helpful.

It is not a good idea to recommend and use fertilizer N on legumes but people do.  That is good place to start a more targeted fertilizer use approach.

On the crop Maize Nitrogen can be reduced according the soil nitrate level taken when the crop is 15 centimeter high. The Pennsylvania State University suggests that starter fertilizer always be used and if the soil nitrate level is superior to 20 ppm Nitrate the application of sidedress Nitrogen can be avoided.

This sidedress soil testing procedure can be effectively used and was first worked up at Iowa State University. By targeting the application and rate of this fertilizer the cost and environmental impacts can be reduced.

In order to take advantage of these approaches knowledge of proper placement and time and analysis is needed to optimize the systems which are often limited by equipment availability and sophistication and experience of farmers.

The ability to both optimize crop production and reduce inputs in fertilization depends on both soil and plant analyses and a considerable knowledge of the meaning of the testing for their interpretation. The Knowledge and testing of the interpretation is many times the most limiting step or bottleneck.

Some body has to compare farmers'eye judgement (available for all crops ) and leaf colour chart (available for a few crops) and say which is better.Was there any study to compare soil mineral nitrogen test and leaf colour  chart for recommending N fertilizer?

I agree with you Dr Hepperly , we need to optimize the crop production with reduced cost of inputs , and at the same  time without incurring any nutrient mining from your soil . therefore , our soil test interpretation has to be farmers friendly , backed by robust calibration models having utmost predictability about the fertilizer requirement based on a given soil test value  and for a given yield target .