Agroclimatic zones of India

Ø  Agro ecological zone is defined as a land unit in terms of major climates, suitable for certain ranges of crops and cultivars

Ø  Caster in 1954, using Thonthwaite’s system of climatic classification and has described 6 climatic regions. Subsequently attempts have been made for climate mapping in terms of moisture and thermal regions. Since rainfall varies from 100-12,000 mm, 27 different soil types are recognized. Among 27, four group of soil are more prominent e.g. (I) Alluvial, (II) Black, (III) Red and (IV) Laterite Soils.

Ø  The ICAR (Indian Council of Agricultural Research, New Delhi, has recognized 8 Agro climatic zones for effective land use planning as given below.

Agroclimatic Zones of India

1)     Humid western Himalayan Region

                  States Includes: Jammu and Kashmir, Himachal Pradesh, Kumaon and Garhwal in                           Uttaranchal

2)     Humid Bengal-Assam Region

                  West Bengal and Assam

3)     Humid Eastern Himalayan Region

                  Bay Islands, Arunachal Pradesh, Nagaland, Manipur, Mizorum, Tripura, Sikkim,                             Meghalaya, and Andaman and Nikobar Islands

4)     Sub-Humid Sutlez-Ganga Alluvial Plains

                   Punjab, Delhi, Uttar Pradesh plains and Bihar

5)     Sub-Humid to Humid Eastern and South Eastern Islands

                   Eastern Madhya Pradesh, Orissa and Andhra Pradesh

6)     Arid Western Plains

                   Haryana, Rajasthan, Gujarat, Dadra and Nagar Haveli, Daman and Diu

7)     Semi-arid Lava Plateauses and Central Islans

                   Maharastra, Western Central Madhya Pradesh and Goa

8)     Humid to Semi-arid western Ghats

                  Karnataka, Tamil Nadu, Kerala, Pondicherry and Lakshadweep Islands

• Ø  During 1985-90, the Planning Commission accepted 15 broad agroclimatic zones based on physiography and climate for effective planning. These zones are: 1, Western Himalayan Region; 2, Eastern Himalayan 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; 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 Ghats; 13, Gujarat Plains and Hills Region; 14, Western Dry Region; and 15, The Island Region.
• Ø Under National Agricultural Research Project (NARP) each agroclimatic zone is divided into sub-zones. The sub-zones totalling 120, are primarily based on rainfall, existing cropping pattern and administrative units, wherein each state is devided into 2-12 sub-zones. These delineations are too many for planning process at national level, having similar agro climatic conditions. The NBSS & LUP, Nagpur, delineated the country into 21 agro ecological regions, using physiographic, soils bioclimatic types and growing periods. Growing period (GP) was based on water balance starting with period having precipitation 0.5 excess of evaporation (PET) ending with utilization of 100mm of stored soil moisture once precipitation falls below PET.
• Ø In this system of delineation, arid zone had GP of 90 days, semi-arid region corresponded to 90-:-150 days of GP, and the sub-arid zone correlated with region having GP between 150 and 210 days. The humid and pre-humid zones had GP of 210-270 days and more than 270 days/year respectively. These zones are:

1)    Western Himalaya, cold arid ecoregion with shallow skeletal soils and length of GP < 90 days.

2)    Western Plain and Kutch Peninsula, hot arid and ecoregion with desert and saline soils and GP < 90 days.

3)    Deccan Plateau, hot arid ecoregion with mixed red and black soils and GP < 90 days.

4)    Northern Plain and Central Highlands, hot semi-arid ecoregion with alluvium-derived soils and GP 90-150 days.

5)  Central (Malwa) Highlands and Kathiawar Peninsular, hot semi-arid ecoregion with medium and deep black soils and GP 90-150 days.

6)    Deccan Plateau, hot semi-arid ecoregion with shallow and medium (inclusion of deep) black soils and GP 90-150 days.

7)  Deccan Plateau and Eastern Ghats, hot semi-arid ecoregion with red and black soils and GP 90-150 days.

8)   Eastern Ghats (TN uplands) and Deccan Plateau, hot semi-arid ecoregion with red loamy soils and GP 90-150 days.

9)   Northern Plains, hot sub-humid ecoregion with alluvium-derived soils and  GP 150-180 days.

10)  Central Highlands (Malwa and Bundelkhand), hot subhumid ecoregion with medium and deep black soils and GP 90-150 days.

11) Deccan Plateau and Central Highlands (Bundelkhand) hot sub-humid ecoregion with mixed red and black soils and GP 150-180 days.

12) Eastern Plateau (Chhatisgarh), hot sub-humid ecoregion with red and yellow soils and GP 150-180 days.

13) Eastern (Chhota-Nagpur) Plateau and Eastern Ghats, hot sub-humid ecoregion with red loamy soils and GP 150-180 days.

14) Eastern Plain, hot sub-humid ecoregion with alluvium-derived soils and GP 180-210 days.

15) Western Himalayas, warm sub-humid (inclusion of humid) ecoregion with brown forest and podzolic soils and GP 80-210 (+) days.

16)  Assam and Bengal Plains, hot humid ecoregion with alluvium-derived soils and GP < 210 days.

17) Eastern Himalayas, warm perhumid ecoregion with brown and red hill soils and GP < 210 days.

18) North-Eastern Hills (Purvachal), warm perhumid ecoregion with red and   lateritic soils and GP < 210 days.

19) Eastern Coastal Plains, hot sub-humid ecoregion with alluvium-derived        soils and GP 150-210 days.

20)  Western Ghats and Coastal Plains, hot humid-perhumid ecoregion with red   lateritic and alluvium soils and> 210 days.

21)   Islands of Andaman-Nicobar and Lakshadweep, hot perhumid ecoregion    with red loamy sandy soils and GP < 210 days.

Ø Agro ecological zones delineated in this system are comprehensive and can be used for the delineation of horticultural and plantation crops cultivation zone added with the data from field experiments considering its perennial nature, differential response to soil moisture for growth, production and quality added with disease and pest problems.