Mr.Nayak,First step is geo-referenced soil fertility assessment ,mapping and fertilizer recommendations, is collection of geo-referenced soil samples using GPS and appropriate sampling procedure.Next stage is sample analysis using appropriate methods for different micronutrients .Then using spatial variability models ,one has to arrive  at appropriate model for preparation of fertility maps. Next step is superimposing  fertilizer recommendations over the fertility maps using GIS software. After superimposing recommendations, one can test or validate the recommendations whether they are appropriate or not by collecting soil samples from farmers' fields .This type of work has been done by IISS,Bhopal and AICRP on STCR cooperating centres. Now on line recommendations are available for many  crops for major nutrients.One can visit the website of IISS,Bhopal and TNAU,Coimbatore.

If you have a zone affected by iron chlorosis for example. Sensors on a tractor can be set up with a Ground Position System which would map your field for the chlorosis. Potentially the system could be linked with default when the chlorosis of lack of greenness reacted a certain level it would trigger a chelated iron spray which would turn off when the appropriate green level was apparent. Chlorophyll readers are call SPAD units. One your map the field for the issue of iron chlorosis it would indicate that those areas would require a land application of lime before the next crop cycle. You would have to be aware that calcitic or alkaline chlorosis was the issue and other chlorosis issues were under control to do this.

Mr.Nayak,From soil fertility information/data one can generate spatial soil fertility maps using GIS tools. The fertilizer recommendations are superimposed on the  digitized soil fertility maps.Farmers and agricultural extension workers can access the recommendations by providing the GPS location, soil fertility or other related information.

Dr.A. Subba Rao ,Sir by collecting soil samples & analyzing them by using GIS  i can create existing soil fertility maps of particular area, for fertilizers recommendations in India, from which departments/institutions i can asses the information/data ?

Thank you sir.

In Karnataka state, the ICRISAT,Patancheru and State Agricultural Department in collaboration have generated  a lot of information on macro and micronutrient status in  soils of different districts.This information you may get by referring to the publications of Suhas P.Wani in research gate. Under Soil Test Crop Response Correlation project (ICAR),Department of Soil Science, Agricultural College,University of Agricultural Sciences Hebbal,Bangalore also generated soil fertility information in respect of macro and micronutrients in different districts of Karnataka.The STCR project has also generated soil test based recommendations for all important crops of Karnataka state.

It is not very clear what you mean by modelling micro-nutrients. Do you mean spatial distribution? 

Dr.Dilip kumar Pal , yes sir i mean spatial distribution of micro nutrients .

In such case we need to think about the scale of mapping. We must remember that the boundary created by a any software may not be a real boundary,which makes recommendations unrealistic.

Dr.Pal,Please elaborate your  view on superimposing fertilizer recommendations on geo-referenced  digitized soil fertility maps.

Such exercise will always remain  fraught with  some  uncertainties  for a better recommendations because of lack of adequate number of spatially associated data on macro- and micro- nutrients.

Dr.Pal, in new initiatives we can go for more number of samples.Now many state govt. are going for issuing soil health cards to every farmer.We have to think on how to utilize such vast data to improve our fertility maps and recommendation system.

One important issue still remains untouched and that is the collection of data in mean weighted value in the fist 100 cm  of the soil profile,which has tremendous relevance to deep rooted crops of the SAT. Sadly we are not giving due attention of subsoil nutritional data.

I am working on micronutrients, PA and GIS since the early 1980´s and the answer is simply: it will help nothing! Reason: a: soil concentration (even if available fractions are considered) tell very little about the actual nutritional status of a cropp; b: therefore micronutrients if deficient in a crop are mostly applied through spraying; c: as one colleague mentioned already: data collection is the technical isssue what wrecks it finally!

Dr.Schnug,all the  three points mentioned by you are important .Real problem is how to tackle the issues raised.We have been complementarily using soil tests and plant analysis in our micronutrient deficiency diagnostic work in different states.We are quite successful in India in diagnosis and management of micronutrient problems.But if we desire  to get country picture or state-wise information, reaching up  to village level, it is humanly impossible to collect ,process and analyze plant samples. So as an alternative we have to go for soil analysis which can be handled on large scale.The data collection can be improved.

Dear Vinod

You can read these papers.

Best Regards

 Mr.Ahmad,Thank you for attaching good literature on the subject.Spectral reflectance measurements using remote sensing,may give good idea of organic matter,soil moisture and soil salinity etc. but it is difficult to measure plant nutrients( or micronutrients)using remote sensing.I request the participants to give their  view or experiences.