You may find this helpful, but it is always appropriate to consult a soil scientist if you have specific needs, and you should have some idea of why your soil is too acidic or alkaline for what you want to grow.  The pH can affect nutrient availability too, important for some plants to produce optimum results.  This link is a good start, but may not be specific enough for your soil or fertilizer need situation, and that is why a guide from your country or local agricultural extension may consider things that would not be associated with this guide from California.  

 http://vric.ucdavis.edu/pdf/Soil/ChangingpHinSoil.pdf

Thank u very much Dr. Hansen for your fruitful suggestions.

Dear,

I agree with Dr. Hansen. The pH of a soil is not just the result of chemical ions in the soil solution. It is more complex than we can think. In the soil nothing is visible with naked eyes. Billions of bacteria, fungi, etc., are surviving in the soil and they are secreting some substances, which ultimately determine the physico-chemical status of a soil.

You should determine your own method by taking the aim in mind. The method adapted should not be interfering to the other factors which may adversely affect your results.

Kind Regards.

Dear Sosanka PROTIM Sandilya, Yes, it is possible to change and adjust the pH of a plot. You have to be very specific with the objectives. As in acidic soils it is being changed and adjusted by using lime and in sodic/alkali soils it is being changed/adjusted by adding gypsum. Thanks

This is very much within the possible reach, to change the soil pH of entire plot , depending upon the objective of your study .  Application soil amendments facilitates such changes in soil pH quite remarkably. 

Thank u very much Ovaid, Dubey Sir and Anoop Sir for your commendable suggestions.

It is possible to change the acidity or alkalinity of the soil or water. Process  are  published and  available on line too.

Thank u Saxena Sir

The very principle of land reclamation is intended for the change in soil pH and electrical conductivity adopting the technology on entire piece of land selected for the purpose. The period of reclamation depends on the magnitude of change in pH. Wider the difference in pH, longer the period, particularly in case of highly buffered soil. Mr. Sosanka has to define the current status of soil properties and objectives of research etc instead of being abstract and incomplete in providing information. 

Dear Dr. Reddy

It was actually a question raised to me by an interviewer and I do not have much knowledge in this aspect. I asked it to the experts of RG only to gain knowledge.

Well taken Mr.Sosanka. I hope the replies provided are adequate for you. If not please feel free to seek further clarification. Thank you.

Thank u very much for your response Dr. Reddy. Hope to have much from you in the future.

If you want to reclaim or adjust pH.First plough the field to bring uniformity in soil spread.  Then divide land into smaller plots and see the variation in each plot or randomly assess. Accordingly pH can be adjusted in applying measured quantity of amendments depending upon the soil pH in each plot. You need to standardize.

Thanks Malhotra Sir for your valuable response

Actually in which was do you want to adjust the pH. from acid to neutr or alkaline to neutr. form acid to neutr you can do it promptly by dividing the field into plots. I suggest you to determine the lime requirement on plot base.

Thank u Dr.Veli for your response.

Dear Dr. Sosanka PROTIM Sandilya

According to pH of your soil (say for acid or alkaline status) , You need to calculate Lime requirement of the acid soil and gypsum requirement of your alkaline soil. Accordingly, the desired amount of calculated lime or gypsum need to be added to the soil at the rate of 1/10th of LR or GR in every cropping season near the rhizosphere zone in line sowing for getting best result.

I dont think , it should be any more difficult to bring change in soil pH in a plot , regardless of dose or the type of amendment being applied . Although ,  the natural spatial variability in pH will always exist , despite the effective impact of soil amendments.

The researcher should first determine the soil pH and compare the difference with soil neutral pH 7.This will help to calculate the liming requirement of Ca and Mg based compounds to apply and it should be noted that overliming or underliming is very dangerous to the stabilization of soil equilbrium

Dear Dr. Naik, I would like to inform you that I am not Dr. Sandilya. Actually I am still pursuing my Ph.D. Any way thank u so much for your reply. 

The things that might be added are that there are laboratory tests to estimate the dose, and if the site is very spatially variable it may be useful to useful to map the patterns and use them as the basis of differential application.  Even with fine lime and good incorporation, the mixing will be imperfect.  The net result on plant performance may consequently vary between seasons, especially if subsoil acidity is the problem, e.g. for root access to subsoil moisture.  Lastly, if you are liming, please consider the cation balance and that penetration below the incorporation depth may be slow. 

Thank u very much Dr. Anoop, Dr. Moyin and Dr. Paul for your valuable suggestions.