Jasbir Singh (1975) has determined two-tier crop combinations on the basis of the primary and secondary crops for agricultural regionalisation of the country. He has identified 12 major and 60 secondary crop associations in the country.
1. Rice Region
This includes most of the eastern India, east and west coastal plains and Kashmir valley. Here average annual rainfall is 100-200 cm. It has 21 secondary crop associations.
2. Jowar Region
ADVERTISEMENTS:
This region spreads over south-eastern Maharashtra, western Andhra Pradesh, western Madhya Pradesh and interior Karnataka on the areas of recur soils enjoying average annual rainfall between 50 cm and 100 cm. It constitutes 9 lower order crop associations.
3. Bajra Region
Bajra region incorporates dry western part of the country consisting of Rajasthan (except Ganganagar district), Kachchh peninsula, and Dhule- Nashik area of Maharashtra. Its secondary crops include jowar, ragi, pulses and oilseeds. It is subdivided into 5 crop associations.
4. Wheat Region
ADVERTISEMENTS:
It encompasses Punjab, Haryana, western Uttar Pradesh, western Vindhyan region and eastern Malwa plateau. It forms 8 secondary combinations with cotton, sugarcane, rice or maize in irrigated areas and gram, bajra, pulses or oilseeds in rain-fed areas.
5. Cotton Region
Cotton, occyping black soil areas of Maharashtra, Gujarat and Malwa plateau as a main crop, constitutes four-crop associations on the basis of secondary crops: cotton-jowar, cotton-millets, cotton jowar-fodder-rice (south Gujarat plains) and cotton-jowar-pulses-oil seeds.
6. Oilseeds (Groundnut) Region
ADVERTISEMENTS:
This region includes Kathiawar, southern Andhra Pradesh and Salem-Coimbatore region of Tamil Nadu. It has two secondary crop associations: (a) groundnut-jowar-bajra (Kathiawar), and (b) groundnut-jowar-rice-pulses (Tamil Nadu upland, upper Kaveri basin and Rayalseema plateau).
7. Gram Region
It occupies mixed red-black soil region of Bundelkhand (Uttar Pradesh) and Ganganagar-Hissar- Bathinda zone of Rajasthan-Punjab. While former is dominated by gram-wheat-millet secondary crop association, the latter has two lower order regions of (a) gram-oil-seeds-jowar-fodder-maize, and (b) gram- bajra-fodder-wheat.
8. Maize Region
ADVERTISEMENTS:
Maize assumes significance in Jammu and Kashmir (Doda and Udhampur), Himachal Pradesh (Chamb), and eastern Rajasthan plateau. It constitutes three secondary crop associations: (a) maize- wheat-rice, (b) maize-rice-millets, and (c) maize- wheat-oilseeds-cotton.
9. Ragi Region
Ragi occupies a prominent place in the rain shadow zone of southern Karnataka. It constitutes two crop associations: (a) ragi as a mono crop, and (b) ragi-oilseeds-rice-pulses.
10. Barley Region
ADVERTISEMENTS:
Barley is a primary crop in the upper reaches of the hills of Uttaranchal and Himachal Pradesh. It forms a crop association of barley-wheat- pulses.
11. Orchard Region
Orchard crops are dominant in southern Kerala. These form crop association with plantation crops (spices, rubber)-coconut-rice.
12. Tea Region
ADVERTISEMENTS:
Tea is grown in north-east India (Assam and West Bengal) and in the Nilgiris (Tamil Nadu). It forms a crop association with coffee in the Nilgiris.