Preface
A systematic appraisal of the soil and climatic resources is a pre-requisite for formulating effective land use plan for various regions of our country. Mapping of the various agro- ecological regions will help in identifying suitable cropping patterns for a particular region.

There are several classifications of agro-climatic regions and soils proposed by several agencies. The reader is advised to study the earlier articless on the related topics Land Capability Classification and Agro-climatic Divisions of India. This article is on the agro-ecological regions of India; but there may be several things similar to the article on Agro-climatic Divisions of India. We must keep in mind the distinction between agroclimatic divisions and agro-ecological regions even though there may be similarities.

Introduction
Indian sub-continent exhibits a variety of landscapes and climatic conditions which are noticeable in the types of soils and vegetation. Needless to say that there exists a significant relationship between climate, soils, type of land and vegetation. While preparing for land use plan or a cropping pattern or agricultural or animal husbandry system we should keep In mind the combine effect of climate, soil, land formation, topography and vegetation of the place.

In the past, several attempts have been made to understand and classify the agro-climatic regions as well as the agro-ecological regions of our country. In the year 1954, Carter divided India into six climatic regions, ranging from arid to perhumid, based on the criteria of Thornthwhite system of climatic classification. Murthy and Pandey (1978) on the basis of physiography, climate (rainfall and potential water surplus/deficit), soils and agricultural regions identified eight agroecological regions. Though this was a good beginning this system of classification suffered from some limitations. Based on the data of 160 meteorological stations in the country and using the concept of moisture adequacy index Subramaniam (1983) proposed 29 agro-ecological zones with the possible 36 combinations of moisture adequacy index and dominant soil groups following the pattern of FAO/UNESCO. Sehgal et al.(1987) prepared a computerized bio-climatic map of North West India, based on the criteria of dry month (the month having the real moisture deficit of 40% or more of the potential evapo-transpiration- PET). Krishnaft (1988) delineated 40 soil-climatic zones based on major soil types and moisture index.

Planning Commission as part of the mid-term appraisal of the planning targets of VII Plan (1985-1990) divided the country into 15 broad agro-climatic zones based on physiography and climate. They are the following:

1. Western Himalayan Region, 2. Eastern Himalayan I Region, 3. Lower Gangetic Plains Region, 4. Middle Gangetic Plains Region, 5. Upper Gangetic Plains Region, 6. Trans-Gangetic Plains Region, 7. Eastern Plateau and Hills Region, I 8. Central Plateau and Hills Region, 9. Western Plateau and Hills Region,10. Southern Plateau and Hills Region, 11. East Coast Plains and Hills Region, 12. West Coast plains and Hills Region, 13. Gujarat Plains and Hills Region, 14. Western Dry Region and 15. The Island Region.

The state agricultural universities were entrusted with the task of dividing these agroclimatic zones into state-wise sub-agro-climatic zones under the National Agricultural Research Project (NARP). Accordingly 127 sub zones were identified based on the rainfall, existing cropping pattern and administrative units. For the sub-zones classification refer article Agro-climatic Divisions of India.

The government of India was not satisfied with the classifications done so far. It further entrusted the National Bureau of Soil Survey and Land Use Planning (NBSS&LUP) of Indian Council of Agricultural Research to prepare an agro-ecological region map of the country based on the parameters (rainfall, temperature, vegetation, potential evapo-transpiration) which form the -Bioclimate- and parameters (rainfall, potential evapotranspiration, soil storage) which constitutes the - Length of the Growing Period -(LGP) and parameters (soils and physiography) which form the - Soil or Land Scape. This article describes this classification.

II. Basis of Classification

The parameters taken for the classification agro-ecological regions are the characteristics of: physiographical features, soil characteristics, bio-climatic types and length of the growing period. These are explained one by one briefly.

A. Physiographic features

The major physiographic regions in our country are the Mountainous region, Indo-Gangetic Alluvial Plains, Peninsular or Deccan Plateau and Coastal Plains. These are further divided into 19 broad and basic agro-ecological regions. Each region is represented by a capital letter of the English alpha- bets as given here.

1. Westem Himalayas

This includes Ladakh plateau, Kashmir Himalayas, Punjab Himalayas and Kumaun Himalayas of Uttar Pradesh and is symbolized by - A.

2. Central Himalayas

This includes mainly Nepal Himalayas, and foot-hills of V.P. Himalayas and is symbolized by - B.


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