The Rice–Wheat Cropping System

The rice-wheat rotation is the principal cropping system in south Asian countries that occupies about 13.5 million hectares in the Indo-Gangetic Plains (IGP), of which 10 million hectares are in India, 2.2 million hectares in Pakistan, 0.8 million hectares in Bangladesh and 0.5 million hectares in Nepal. This system covers about 33% of the total rice area and 42% of the total wheat area in the four countries as stated above, and account for one quarter to one third of the total rice and wheat production. This cropping system is dominant in most Indian states, such as Punjab, Haryana, Bihar, Uttar Pradesh and Madhya Pradesh, and contributes to 75% of the national food grain production. This cropping system is also very prevalent in Himachal Pradesh and Jammu & Kashmir, especially the Jammu region. There was a time when the yield of paddy was the highest, i.e. more than 4.2 t ha⁻¹ in the valley of Kashmir among the north-western Himalayan states, but now it has reduced considerably. Thus, the rice-wheat cropping system is the cornerstone of India's food self-sufficiency. The environmental requirements for the growth and development of both rice and wheat crops are contrastingly different. Rice grows best under stagnant water conditions, while wheat requires a well-pulverized soil with a proper balance of moisture, air and thermal regime. Therefore, a dominating feature of the rice-wheat cropping system is the annual conversion of soil from aerobic to anaerobic and then back to aerobic conditions.