Preface

I. Introduction
II. Climatic Divisions of India
A. Based on potential evapo-transpiration
B. Based on periodic climate change
III. List of Agro-climatic Zones of India
IV. Conclusion


Preface
Agriculture is determined by the climate. In other words, climate is the key factor in any operation of agricultural production right from field preparation to marketing. The success and failure of farming is closely associated with the prevailing weather conditions. Hence, it is possible to optimize the farm production by adjusting the cropping patterns and agronomic practices to suit the climate of an area if we have a fairly good knowledge about the agro climatic regions of our country. Closely related are the division of agro-ecological regions of our country. In many instances these divisions may be same or very similar. Therefore, the reader is advised to study the article on Agroecological Regions of India. So by knowing climate of a particular area, it would be possible to plan the production strategies suitable to that area in a better way. This article provide useful information and list of different agro-climatic regions of the country.

Introduction
Agro-meteorology, abbreviated from Agricultural Meteorology and also referred to as Agro-climatology, has been defined in several ways. The name itself implies that it is the study of those aspects of meteorology which have direct relevance to agriculture. Agrometeorology puts the science of meteorology to the service of agriculture, in its various forms and facets, to help the sensible use of land, accelerate production of food and to avoid the irreversible abuse of land re- sources.

The task of an agrometeorologist is to apply every relevant meteorological skill to help the farmer to make the most efficient use of his physical environment for improving agricultural production both in quality and quantity.

To have a better understanding of the agro-climatic divisions of India the reader is advised to study also the article - Agro-ecological Regions of India.

II. Climatic Divisions of India

To work out the suitable cropping plan for field crops in different agro-climatic regions of the country, it is essential to .know how the country is divided into homogeneous climatic regions. Sub-divisions can be formed on the basis of (a) potential evapo-transpiration, or on the basis of the (b) periodic occurrence of temperature conditions favourable for the growth of annual crops.

A. Based on potential evapo-transpiration

Under this climate has been classified on the basis of potential evapo-transpiration which represents a climatic index of plant development and a heat index of the agro- climate, soil moisture supply, plant cover and soil management. Among these, first two are of far greater importance than the other factors. According to this classification, the country may be divided into four climatic regions, as detailed in table

S.NO.	Climatic Type	Index or potential Evapo- transpiration	Region & State covered
1.	Arid	-40 to -60	West Rajasthan
2.	Semi-Arid	-20 to -40	Northern & Eastern Rajasthan, Gujarat, Marathwada, Mysorte, Rayalaseema, Punjab, Delhi, Western U.P
3.	Sub-humid	-20 to +20	Central U.P, Western & Central M.P, Vidarbha, Eastern U.P, Bihar, Sub-mountain tracts of U.P, H.P., West Bengal and nilgiri
	humid	+20 to 100	Konkan, Kerala, Coastal Madras, Assam, Orissa, West Bengal, Eastern M.P and coastal Andhra Pradesh

Each of these regions are further explained.

1. Arid region

In the arid region, the rainfall is below 30 cm and fluctuation in rainfall is of the order of -49 per cent. One in every five is extremely lean year and one in five has abundance of rainfall. In other years the precipitation approaches normal but the distribution of rainfall is extremely uncertain even in the rainy season. Drought resistant types of crops like jowar, bajra etc. are grown during the monsoon season. Production of crop is extremely precarious. A good crop may be expected once in five years, the rest are usually below normal.

Climatically, the area is more suitable for production of livestock than for cultivation of crops. It is presumed that by adaptation of better standards of livestock feeding and improving cattle management practices, greater return can be achieved. This will require introduction of improved methods of grass land management and readjustment of cultivation of crops supplementary to livestock production which will result in a more stable form of land use than hitherto.

2. Semi-arid zone

This is the dry farming region of the country and roughly covers an area of 77 million acres. Except in the Punjab and Western Uttar Pradesh, there are large scale irrigation projects to provide protective irrigation to the crops. The cultivated crops else where have to depend largely upon the erratic monsoon rains which occur within the specified periods. As the coefficient of variation of rainfall is 15-25%, there occurs wide variations in the yield of crops grown under unirrigated conditions. The important crops grown in this region are millets, ragi, cotton, groundnut, castor and linseed. Evolving drought resistant strains of crops is the most fruitful line of research. Introduction of such strains obtaining maximum population, efficient use of soil moisture and application of fertilizers are important for increased crop production.,

3. Sub-humid zone

This climatic complex consists of temperate sub-tropical conditions. The region is important for the production of wheat, rice, sugarcane, jowar, arhar, maize and mustard. This region is potentially very productive. Rains may occur often. The coefficient of variation of rainfall is less than -20 per cent. By proper management of land, water and cropping the yields can be appreciably stepped up. Introduction of short duration varieties of crop, application of organic manures to increase moisture holding capacity of the soil and judicial application of fertilizers and proper management of land are essential to increase crop production in these regions.

Next : Agroclimatic Divisions of India - Humid Zone