CLIMATE. The Indo-Gangetic plains form the most important wheat area. The cool winters and the hot summers are very conducive to a good crop of wheat. Based on agroclimatic conditions, the country is broadly divided into five wheat zones. These are as follows:
(i) The North- Western Plains Zone consisting of the plains of Punjab, Haryana, Jammu, Rajasthan (except the south-eastern portion) and western Uttar Pradesh. Here, the irrigated wheat is planted in November and the rain-fed wheat towards the end of October. Harvesting generally starts by the middle of May. This zone is most important among the five zones, and only T. aestivum is exclusively grown there.
(ii) The North-eastern Plains Zone consisting of eastern Uttar Pradesh, Bihar, West Bengal, Assam, Orissa, Manipur, Tripura, Nagaland, Meghalaya, Mizoram, Arunachal and Sikkim. This is also an exclusively T. aestivum area. Owing to the late harvesting of paddy, most of the sowing of the wheat is generally done towards the latter half of November and in the first fortnight of December. Harvesting is done in March- April.
(iii) The Central Zone consists of Madhya Pradesh, Gujarat, south-eastern Rajasthan (Kota and Udaipur divisions) and the Bundelkhand area of Uttar Pradesh. Most of the wheat area (about 75 per cent) in this zone is rain-fed. Both T. aestivum and T. durum are grown in this zone. T. dicoccum is grown in a few pockets in Gujarat. Being predominantly rain-fed, the sowing of wheat in this area depends on the conserved moisture of the soil from the preceding monsoon. Sowing in the rain-fed area commences from the middle of October and goes up to the end of the month. Irrigated wheat, whose acreage varies from state to state in this zone, is panted mostly in November. Harvesting here is a little earlier than in the other two zones mentioned and it commences by the end of February and most of it is over by March. The best – quality durum wheats are produced in this zone. The crop is subjected to occasional frost in the Narbada Valley area of Madhya Pradesh.
(iv) The peninsular zone consists of the southern states of Maharashtra, Andhra Pradesh, Karnataka and Tamil Nadu. All the three species mentioned above, namely aestivum, durum, dicoccum, are grown in this zone. T. durum is the most important species under rain-fed conditions are practically over in October and the irrigated sowings in the first fortnight of November. Most of the harvesting is over in the second half of February. Assured water supply is limited in this zone, but wherever it is available, a good crop of wheat comparable with what is obtained in north-western India is raised.
(v) The northern hill zone consists of the hilly areas of Kashmir, Himachal Pradesh, Uttar Pradesh, West Bengal, Assam and Sikkim. In this zone, the sowing is done in October and the harvesting is done in May-June. The wheat plants remain practically dormant during the cold months from November to March and as the temperature rises in April, the crop starts growing. Wheat is grown in this hill zone up to elevations of 3,658 m above sea level. In the valleys and high mountain ranges, wheat is grown in summer instead of in winter. Here, it is sown in April-May and harvested in September -October. In the northern hill zone, only T. aestivum is grown.
Throughout India, only spring wheats are grown, although they are raised in winter.
In the southern hills of Tamil Nadu, two crops of wheat are raised in a year. The first crop is taken between October-April and the second crop in May-September.
The annual rainfall in all the wheat growing zones ranges from 12.5 to 100 cm. But most of this rain is received in summer or during the monsoon. In winter when the wheat is in the field, the rainfall ranges anywhere between 3 and 7 cm. To get good yield irrigation is essential and this enables the farmer to provide the necessary inputs. Irrigation facilities range very widely in different states. In Punjab, about 85 per cent of the wheat crop receives irrigation, whereas in states, like Maharashtra, Karantaka, Madhya Pradesh, only 13-25 per cent of the wheat area is irrigated. The high temperatures on both ends of the wheat season restrict the cultivation of this crop in India to the cooler months. High temperatures in September do not permit good tillering of the crop. They are also favourable to root rot and seedling blight fungi. The hot summer during the grain ripening period hastens the maturity of the crop.
Before the ‘Wheat Revolution’,different wheat varieties were grown in each of the zones based on their maturity periods. But with the availability of photo-insensitive varieties in recent years, the same varieties could be grown from the high Himalayas to Cape Comorin. Wheat cultivation has spread to the rice growing areas of eastern India in recent years in a big way. However, the pre monsoon showers towards the end of March force the harvesting of the wheat crop by the third week of this month.
SOILS. Well drained loams and clayey loams are considered to be good for wheat. However, good crops of wheat are raised in sandy loams and the black soils also. In the past, it was considered that durum wheats were more suitable for cultivation in black soils than the aestivums. But this is not true with the present day aestivum wheats which are grown in all types of soils in the country.
ROTATION. Normally, the rabi, wheat is followed in kharif by crops, such as maize, jowar, bajra, cotton, and arhar. Sometimes, some of the green-manure crops such as sanai, moog, guar, lobia or hubam clover, are sown immediately after kharif to enrich the soil. Gram,linseed,barley and mustard are also included in rotations. With the recent emphasis on intensive agriculture the rotation patterns have undergone some changes. In Punjab, Haryana and western U.P., rice has become an important crop in the kharif. It is followed by wheat. In eastern India ,wheat has become an important crop and is grown extensively after rice on land which is left either fallow or put under boro rice. In some states like West Bengal, the rice wheat jute rotation has become common. The sugarcane wheat rotation is also common in northern India. Where irrigation is available and legume crop is grown in between two serial crops to enrich the soil as well as to get the needed pulses.
In the black soils of central and peninsular India, unirrigated wheat is rotated with jowar , bajra or cotton in kharif in the preceding year. The growing of quick maturing crops such as mung, gingelly, onion, coriander and even groundnut or early sown maize such as catch crops before wheat are fairly common. The irrigated wheat rotated with variety of garden crops and irrigated rice, rabi jowar, ragi (Eleusine coracana) etc.
All over India, the growing of wheat mixed with barley, mustard ,gram lentil and safflower is quiet common, A row of mustard or safflower for every 8-12 rows of wheat is put. This mixed cropping meets the family requirement for cereals, pulses and oil and also gives some insurance against pests, diseases and other natural calamities which may destroy the single corp. north western India and in tarai areas of U.P., wheat is grown as companion crop with row crops e.g.- sugarcane. About 3-4 tonnes of wheat is harvested as bonus in such companion cropping, without affecting the yield or quality of sugarcane.