Agronomic efficiency may be defined as the nutrients accumulated in the above-ground part of the plant or the nutrients recovered within the entire soil-crop-root system. Economic efficiency occurs when farm income is maximized from proper use of nutrient inputs, but it is not easily predicted or always achieved because future yield increases, nutrient costs, and crop prices are not known in advance of the growing season. Environmental efficiency is site-specific and can only be determined by studying local targets vulnerable to nutrient impact. Nutrients not used by the crop are at risk of loss to the environment, but the susceptibility of loss varies with the nutrient, soil and climatic conditions, and landscape. In general, nutrient loss to the environment is only a concern when fertilizers or manures are applied at rates above agronomic need.

equations (1), (2) and (3) Understanding the component effects on nitrogen fertiliser use efficiency (NUEf)

NUEf  =  NUpEf × NUtE…………………………..(1)

NUtE  =  (DM/NUp) × HI……………………….(2)

NUtE  =  NHI/GNC………………………………..(3)

NUEf is nitrogen fertiliser use efficiency, or kilogram of harvested grain per kilogram of nitrogen fertiliser applied (kg/kg N)

NUpEf is the uptake efficiency of fertiliser nitrogen (kg/kg N), or nitrogen uptake by the crop (NUp) measured in kg N/ha, divided by fertiliser nitrogen supply (kg N/ha)

NUtE is the utilisation efficiency of grain production from nitrogen taken up by the crop (kg/kg N).

DM is the total dry matter of the crop at maturity (kg/ha)

HI is the harvest index (grain dry weight divided by total DM, a dimensionless ratio)

NHI is the nitrogen harvest index (the proportion of crop nitrogen uptake in the grain at maturity, a dimensionless ratio)

GNC is the grain nitrogen concentration (w/w, or often given as a percentage).

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Infact , the definition of NUE will remain the same , including the methodology,  you use for meeting out the nutrient requirement of  a crop . We still consider agronomic NUE as best revealing the crop response vis-a-vis NUE ...since there as many 23 definitions of NUE depending upon the choice of the researcher. 

Good points Dr. Anoop. We need to analyse the reasons for low efficiency of fertilizer is mainly attributed to the losses of nitrogen taking place through ammonia volatilization, denitrification, leaching, and runoff. Considering these points we need to work out strategy.

Despite all these analysis Dr Malhotra , the computation on NUE will not change whether it is INM,  or exclusively inorganic fertilization or even organic manuring ,method of computing  agronomic NUE will not change , but off course , there will be distinctive variation in NUE....no doubt...