Respected Sajjad Raza, first you need to collect data on soil texture, order through out the country along with latitude and longitude of each sampling position and collect also soil samples. Then establish any one of the following design as per availability of resources. Then interpolate your data in any GIS-GPS software (eg Arc - GIS) with the help of lat-long data of the respective positions.

http://www.sciencedirect.com/science/article/pii/S0167880905000435

http://download.springer.com/static/pdf/193/art%253A10.1007%252Fs11104-004-0630-8.pdf?originUrl=http%3A%2F%2Flink.springer.com%2Farticle%2F10.1007%2Fs11104-004-0630-8&token2=exp=1464017471~acl=%2Fstatic%2Fpdf%2F193%2Fart%25253A10.1007%25252Fs11104-004-0630-8.pdf%3ForiginUrl%3Dhttp%253A%252F%252Flink.springer.com%252Farticle%252F10.1007%252Fs11104-004-0630-8*~hmac=5f17f1a56e26b4861b53e66b0a12546f8f6130009d8edc5bad3370ce42951a11

http://abe.ufl.edu/carpena/files/pdf/publications/refereed_articles/MonitoringOfNitrateLeaching.pdf

Respected Avijit Ghosh, Many thanks for your precious time and valuable guidance. I'll surely follow the steps and read the papers you attached to get my answer. Many thanks again. Blessings.

According to research findings, at global level the recovery efficiency of applied nitrogen fertilizer is about 33%. However, it varies from soil to soil types, management practices, application methods, crop or varieties of crops and the type of N fertilizer applied. I think to carry out this study, first, you may need to determine or have the information on amount of N loss through leaching. It can be determined both under field and greenhouse conditions.  

Dear Raza: Soils are very complex and, even at national scale (map of 1:100.000 and below) they are presented in a mosaic of distribution. This distribution depends on many variables: climate, relief, parental material, time and agricultural management systems that are expressed then in the soil properties. It is not only the texture...it is also the soil depth, its organic matter level, the disposition of the horizons, the lithic contacts, its biological properties, its moisture, the type of agriculture system (ecological or conventional), the economical possibilities of farmers...and so on, that can interfere on the nitrogen movement. All these and others properties must be taken in account to decide the level of interpretations of your phenomena. Best regards, Tomás