By concentration we generally mean the clus­tering of a recognizable degree of a particular ele­ment in an area. Crop concentration exhibits than different crops when viewed together by superimpose- section depicts areas wherein their regional concentra­tions do not overlap.

For example, on the national scale, the areas of rice concentration in eastern India and the areas of bajra concentration in western Rajasthan do not even partly coincide. Here only a single crop, either rice or bajra, shows a regional concentration. Crop concentration helps us in under­standing the complex agricultural landscape of a region so as to enable us to decide the strategy for agricultural planning.

Both qualitative and quantitative approaches have been used to explain the degree of crop concen­tration. Of these the latter are more precise and accurate. The general concentration of a crop can be measured by the technique using location quotient or coefficient of localization for which different methods have been suggested by Florence (1948), Chisholm (1962), Bhatia (1965) and J. Singh (1976). J. Singh (1976) has used following formulae to measure the crop concentration in India:

Using above formula rice concentration re­gions of India (1969-70) have been identified by Singh and Dhillon (1984, p. 219). Map shows that rice is mainly concentrated in the north­eastern and coastal areas of the country. Very high concentration of rice is noticed (LQ 3-4) in the north-eastern states, Gangetic West Bengal, south Bihar, coastal and northern Orissa; while high con­centration (LQ 2-3) areas include northern West Bengal, central Bihar, Chhattisgarh, southern Orissa, and coastal areas of Andhra Pradesh, Tamil Nadu, Karnataka, Maharashtra, and the Vale of Kashmir Areas of moderate concentration are confined I northern Bihar, eastern Uttar Pradesh, eastern Maharashtra, southern Tamil Nadu and Kerala. Simi­larly low and very low concentration (LQ below 1) areas are found in remaining parts of the country.

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The study of crop concentration is helpful in many ways in deriving relevant conclusions about crop distribution. Higher the crop concentration index, higher is the level of interest in the production of that crop. It helps in taking important decisions regarding marketing, storage, and trading of the crop produce.

In terms of types of concentration, crops may be identified by a single nucleus to multiple nuclei and by high density to low density distribu­tion. Changes in the pattern of concentration may throw light on the expansion and contraction of its high density areas and on the changing core of the crop. The spatial variations in the degree of concen­tration are largely determined by the interaction between various factors such as physiographic, cli­matic, seraphic, hydrological, socio-economic and techno-organizational, etc.