Everything you need to learn about wheat cultivation, harvest and growth.
Introduction to Wheat:
Wheat is one of the most important food crops, which is grown extensively throughout the world. The maximum area under the crop is in USSR, followed by USA and India. In the last named country, wheat is next to rice in importance as a staple food. Wheat is consumed in this country mostly in the form of unleavened, pan-baked bread, called chapati. The grains of wheat contain a substance called gluten, which helps the production of a “risen” loaf, commonly eaten in different countries.
The wheat plant was grown in India in very ancient times and this is indicated by the carbonized grains found in the excavations of Mohen-jo-daro.
There is evidence to support the belief that wheat originated in south-western Asia. According to Vavilov, north-western portion of the Indian subcontinent together with the contiguous regions of Afghanistan was the centre of origin of the common bread wheat, Triticum aestivum.
So far as the genetic origin of wheat is concerned, a number of closely related species, namely, Triticum monococcum, Aegilops speltoides and Aegilops squarrosa are believed to have combined in nature into a polyploid series.
Wheat, which belongs to the genus Triticum may, along with their close relatives, be divided into diploid, tetraploid and hexaploid groups, their somatic chromosome numbers being 14, 28 and 42 respectively. In nature, these wheats perform as diploids.
In the past, 4 species of Triticum were under cultivation in India, of which T. dicoccum Schuble and T. durum Desf. are tetraploids and the other two, namely, T. aestivum L. and T. sphaerococcum Percival are hexaploids. Only three species, namely, T. dicoccum, T. durum and T. aestivum are now commercially grown in this country.
Of these, the first one, T. dicoccum, is grown in the hills of Tamil Nadu and in parts of Karnataka, AP, Maharashtra and Gujarat. T. durum, the macaroni wheat, is the second most important wheat, next only T. aestivum and it occupies about 14% of the wheat area in the country.
It is grown in parts of UP, Rajasthan, MP, Gujarat, Maharashtra and Karnataka. T. aestivum or bread wheat is grown in the entire wheat-growing area of the country except the southern states and it covers about 85% of the total wheat area. The total production of wheat in the country, which was 54.1 million tonnes in 1988-89, is expected to rise further.
Wheat is an annual herb belonging to the family, Gramineae. The plant is erect with elastic cylindrical stem. Leaves flat, linear-lanceolate, acuminate and ligulate; sheaths smooth; ligules short and truncate. Inflorescence or the ear of wheat is an erect, terminal spike, irregularly 4-sided, more or less compact; spikelets solitary, sessile, laterally compressed and few flowered.
Flowers are bisexual, the uppermost sterile. Glumes 2 are persistent, about 1 cm long, rigid, sub-equal, broadly ovate-oblong, obtuse or shortly awned. Lemmas oblong, rounded or keeled on the back, muticous or 1-3 awned. Paleas are as long as lemmas, 2-keeled. Lodicules 2 are entire and ciliate. Stamens3. Ovary superior, 1- celled with anatropous ovule. Style2 is very short. Caryopsis is oblong and ventrally grooved.
Wheat-Growing Zones in India:
Only spring wheats are grown in India, although they are raised mainly in the winter season. The country can be broadly divided into five wheat-zones on the basis of agro-climatic conditions.
They are:
(i) North-Western Plains Zone:
It consists of the plains of Punjab, Haryana, Jammu, Rajasthan (except the south-eastern portion) and western UP. This is the most important of all the zones and it exclusively grows T. aestivem.
(ii) North-Eastern Plains Zone:
It consists of eastern UP, Bihar, West Bengal, Assam, Orissa, Manipur, Tripura, Nagaland, Meghalaya, Mizoram, Arunachal and Sikkim. This zone also grows T. aestivum exclusively.
(iii) Central Zone:
It consists of MP, Gujarat, South-Eastern Rajasthan and the Bundelkhand area of UP. A major portion of the wheat area in this zone is unirrigated and both T. aestivum and T. durum are grown here. T. dicoccum is also grown in a few pockets.
(iv) Peninsular Zone:
It consists of the southern states of Maharashtra, AP, Karnataka and Tamil Nadu. All the three species, namely, T. aestivum, T, durum and T. dicoccum are grown in this zone.
(v) Northern Hill Zone:
It consists of the hilly areas of Kashmir, Himachal Pradesh, UP, West Bengal, Assam and Sikkim. In this zone, only T. aestivum is cultivated and the crop is grown up to elevations of 3,658 m above sea-level. In the valleys and high mountain ranges, wheat is grown in summer.
Climate and Soil Required for Growing Wheat:
The most important wheat area in India is the Indo-Gangetic plain since the cool winters and the hot summers are very conducive to a good crop. Wheat does not grow well in areas where the climate is moist and warm. The growth-period of the crop gets shortened if there is high temperature at either end of the season.
The annual rainfall received in the five different wheat zones mentioned above varies from 12.5 to 100 cm and most of it is received during the summer or the monsoon. During winter, when the wheat crop is in the field, the rainfall may vary from 3 to 7 cm and hence water has to be provided by irrigation. The crop can be grown in India only in cooler months. High temperatures interfere with proper tillering of plants.
Such temperatures also encourage development of root rot and seedling blight diseases. If the temperature during the period of grain ripening is high, the maturity of the crop is hastened. Previously, wheat varieties of different maturity-periods were grown in different zones, but now that photo-insensitive varieties are available, the same varieties can be grown throughout India.
Soil:
Wheat is grown in different types of soils in India. Although loams and clayey loams having good drainage are considered suitable for wheats, good crops can also be raised in sandy loams and black soils. Contrary to the common belief that durum wheats are more suitable for growing in black soils, aestivum wheats are now available, which can be raised in all types of soils in the country.
Rotation of Wheat Crop:
A wheat crop in the Rabi season is normally followed in the kharif by crops, such as, maize, jowar, bajra, cotton and arhar, certain green-manure crops, like sunnhemp, mung, guar, etc., are sometimes raised immediately after the kharif with the object of enriching the soil. Gram, linseed, barley and mustard are also included in the rotations.
With the availability of photo-insensitive crop varieties, considerable emphasis is now laid on intensive agriculture and, as such, rotation patterns have been changed to a certain degree. In the north-western states, namely, Punjab and Haryana, and in western UP, rice is an important crop in the kharif, which is followed by wheat in the Rabi. Sugarcane – wheat rotation is also commonly adopted.
In certain states, where jute is grown, rice-wheat-jute is a popular rotation. A quick – growing crop like mung, til, onion or even groundnut is raised before wheat in some areas. Although wheat is generally grown as a pure crop, raising of mixed crops of wheat with barley, mustard, gram, lentil and safflower is common in India. The practice has been found to be very useful under un- irrigated conditions.
Cultivation of Wheat:
A well-pulverized and compact seed-bed is required since it ensures good and uniform germination of seeds. For raising a dry crop of wheat on alluvial soils, three or four ploughings during the summer and a number of harrowing during the rainy season, followed by three or four cultivations and plankings just before sowing have been found to be very good. It is essential to conserve soil-moisture by timely cultivation.
In the case of the irrigated crop, on the other hand, the land is given a pre-sowing irrigation. Besides, a reduced number of ploughings is necessary for preparation of the seed-bed. If there is a likelihood of attack by white ants or other pests, Aldrin 5% or BHC 10% dust should be applied to the soil at the rate of 25 kg/ha, after the last ploughing or before planking.
Under irrigated conditions, the first half of November is the optimum time for sowing medium long-duration varieties and the second half of the month for short-duration varieties. In the eastern part of India, late harvesting of rice often delays sowing of wheat, sometimes up to the third week of December, whereas in the north-western part of the country, the sowing may be delayed as a result of late harvesting of rice, sugarcane or potato.
In so far as unirrigated conditions are concerned, the second half of October is the optimum time for sowing wheat. High temperatures at the sowing time of wheat adversely affect stand and tillering and the plants are attacked by fungi and insect pests. Besides, flowering takes place quite early. All these cause a depression in the yield of grain.
Sowing:
Sowing of the seed is done by drilling or broadcasting. While row-spacing of 22.5 cm is considered optimum for irrigated, timely-sown wheat, a row-spacing of 15- 18 cm is the optimum for irrigated, late-sown crop. Seeds of dwarf varieties should be sown at a depth of 5-6 cm and those of conventional tall varieties at a depth of 8-9 cm.
In the case of the unirrigated crop, the furrows are left open after sowing, but in the case of the irrigated crop, the furrows are covered by planking. Transplanting of wheat seedlings may be resorted to if sowing is very much delayed.
The seed for sowing must possess good germination capacity. Further, it should be healthy and free from seed-borne diseases. The optimum seed-rate per hectare for bold- seeded and shy-tillering varieties is 100-125 kg., whereas that for varieties, which have medium-sized seed, is 75-100 kg. A larger quantity of seed, as much as 125 kg, is generally used in the case of late-sown crop. A seed-rate of 100 kg per hectare is recommended for sowing under rain-fed conditions.
Irrigation and Weeding:
The crop sown under irrigated conditions usually receives 4-6 irrigations, the first one at the crown-root initiation stage, and the others at late-tillering, late-jointing, flowering, milk and dough stages. Extra irrigations are required if the soil is very light and sandy.
Weeding:
Weeding and intercultural operations are quite important. Hoeing after the first two irrigations is necessary, not only to break the crust, but also to remove the weeds. These objectives are achieved by hand operations also. Further, non-graminaceous broad-leaved-weeds can be controlled by spraying 2, 4-D (0.4 kg a.e/ha in 750 litres of water, 4-6 weeks after sowing), whereas for graminaceous weeds, a pre-emergence application of Tribunil (1.5 kg a.e./ha in 750 litres of water) is effective.
Manuring and Fertilization:
The unirrigated wheat is not generally fertilized. Application of 2-3 tonnes per hectare of farmyard manure or some other organic matter, 5 or 6 weeks before sowing, is desirable. So far as the irrigated crop is concerned, 80-120 kg of nitrogen, 40-60 kg of phosphorus and 40 kg of potash per hectare should be applied.
The quantity of potash is generally decided on the basis of soil-test results. The full dose of phosphorus and that of potash and half the dose of nitrogen should be placed 5 cm below the seed at the time of sowing and the remaining half of nitrogen should be applied at the time of first irrigation, when the crown-root initiation takes place.
Some soils are known to be deficient in zinc and this is responsible for poor yields of wheat. Zinc-deficient soils are found particularly in Punjab, the terai areas of UP, some parts of Haryana, western UP and Delhi. In areas of acute deficiency, 50 kg of zinc sulphate per hectare may be applied, whereas in moderately deficient areas, 25 kg of the chemical would be sufficient.
Harvesting:
Harvesting of the crop is done when the grains become hard and the straw becomes dry. However, the exact time of harvest depends on the crop- growing conditions and also on the area in which it is being grown. In the Peninsular zone of India, harvesting is done from the second half of February to the beginning of March; in the central zone, it is done in March; in the eastern zone, from the second half of March to mid-April; and in the north-western zone, in the second half of April. In the hills, the harvesting time extends from May to June. The same wheat variety matures at different times in the different zones.
The crop is harvested in India, mostly with the sickle. However, the combine is also used in certain parts in the north-west. Threshing is generally done by trampling of plants by bullocks on a threshing floor. Winnowing of grains is generally done with the help of winnowing-baskets. Simple mechanical threshers are commonly used in certain areas, particularly in Punjab.
Low yields of 3 to 4 quintals of grain per hectare may be obtained from un-irrigated crops in the Peninsular or central India. Under irrigated conditions, high yields of 100 to 115 quintals per hectare have been obtained. Contrary to the common belief that best’ yields are obtained in north-western India, it has now been found that similar yields can be obtained from the high-yielding varieties in all the zones provided the correct variety is grown, necessary inputs are made available and the correct production technology is followed. The all-India average for wheat yields varies from 12 to 13.8 quintals per hectare.
Storage:
The grains should be thoroughly dried before they are stored since their storage-life depends to a great extent on their moisture-content. It has been observed that grains having less than 10 per cent moisture can store well.
Milling:
Milling of the grains is done to produce flour. In India, motor-driven flour- mills, using two stones for grinding, are quite common.
Uses of Wheat:
Three main kinds of flour, viz., atta, maida and suji are used for various purposes. The flour is used chiefly for making bread and chapatis and also for making biscuits, cakes, pastries, etc. Beer and other alcoholic beverages are also manufactured from wheat. The wheat straw is a good feed for livestock and is used for stuffing mattresses, for the manufacture of paper, etc.
Varieties of Wheat:
Work pertaining to improvement of wheat was undertaken in India in the beginning of this century at the Indian Agricultural research Institute (IARI), formerly known as Imperial Institute of Agricultural Research, and a few promising varieties were developed. Some of the state departments of agriculture (formerly referred to as provincial departments) also made valuable contributions in this regard.
Later, emphasis was shifted from single-plant selection, as a method of breeding, to hybridization and a number of high-yielding varieties were bred at different centres of research. Particular mention may be made of some of the more popular ones among them, namely, NP 52, 80-5, 114, 120,165, etc. of IARI; C 518, 591 217, 228, 250, etc. of Punjab; Niphad 4, Kenphad 25, 28, 32, 39, etc., of Maharashtra and AO 68, A-113, A-115, etc., of MP.
Continued breeding work led to the development of many more promising varieties, like NP 710, 718, 760, 770, 823, 825, etc., of IARI; C 253, 273, 281, 285, 306, etc., of Punjab; RS 9-11, 31-1, etc., of Rajasthan; Hy 11, 38, 65, 68, 277 of MP; KCN 133, N 179, 345, 747-29, etc., of Maharashtra and K 65, 68, etc., of UP.
Breeding of wheat varieties possessing resistance to diseases, particularly to rusts, all the three species of which can assume serious proportions and cause extensive damage, occupied an important place among the breeding objectives. Systematic work was, therefore, undertaken some time during the fourth decade of the present century at IARI and, subsequently, at a few other centres and this led to the development of varieties possessing resistance to one or more rusts, and, in some cases, to loose smut also.
Particular mention may be made in this connection of NP 809, a variety developed at IARI from a complex cross involving five different parents. This variety was found to be resistant to a number of races of the three rusts and also to loose smut and did well over a large part of the northern hill region.
Some other promising varieties possessing resistance to more than one rust, bred at the same centre, were NP 792, 798, 818, 829, 830, 835, 846, 852, 884, etc. Rust resistant varieties developed at other centres, some of which have been included in the above lists of improved varieties, were C 253, 285, 286, 306, etc., of Punjab; Hy 11, 65, 633, etc., of MP and N 345, NI 747-19, N 917, etc., of Maharashtra.
Besides the work in progress on T. aestivum, attention was also directed to the development of improved varieties of T. durum and T. dicoccum, possessing resistance to rusts. Of the former, mention may be made of NP 404, 406, 412, Meghdoot, etc., of IARI and N 59, NI 146, NI 200, etc., of Maharashtra. With regard to T. dicoccum, NP 200 and 202 are two of the promising varieties developed at IARI and released for cultivation.
In spite of the fact that the tempo of wheat breeding has increased in India to a great extent since independence, the average yield of wheat, which was 665 kg per hectare in 1949-50 rose to only 940 kg per hectare in 1964-65. It was observed that the wheat varieties under cultivation were tall and hence susceptible to lodging.
Application of more than 40 kg of nitrogen per hectare made the plants lodge badly. A search was, therefore, made for short-statured wheats. A few dwarf wheats were obtained from Mexico sometime in the sixties for study under Indian conditions. They were subjected to selection and were also used in hybridization with suitable Indian varieties.
As a result of the breeding work carried out with Mexican wheats in India, quite a few high yielding dwarf varieties were evolved and released for general cultivation. These varieties were responsible for pushing up the average yield of wheat in the country to 1409 kg per hectare (1975-76).
Some of them are Kalyansona, Sonora 64, Sharbati Sonora, Sonalika, Safed Lerma, Chhoti Lerma, Janak, Moti, Girija, UP 301, VL 401, Arjun, Shailaza, UP 262, PV 18, Pratap, D 134, Heera, Shera, etc. Many of these continued to be popular with growers till the end of the seventies. Along with the dwarf aestivum varieties, dwarf durum varieties were also developed for general cultivation.
Research work at various wheat breeding centres in the country has been continued vigorously and many more varieties possessing better yielding ability arid certain other desirable characters have been evolved.
A large number of improved varieties, which have been released during the last ten or twelve years are indicated below along with the areas for which they are suitable:
Diseases of Wheat Crop:
The wheat crop in India is known to be attacked by quite a few diseases. Of the common fungal diseases, rusts are perhaps the most important. Three different rusts attack the wheat plant and, in epidemic years, cause heavy damage to the crop.
They are:
(i) Stripe rust (yellow rust) caused by Puccinia striiformis (P. glumarum), which can be controlled by spraying the crop with Zineb @ 1.70 kg/ha and by treating the seed with Oxycarboxin (0.25%) and by growing resistant varieties.
(ii) Leaf rust (brown rust) caused by Puccinia recondita, which can be controlled by spraying Zineb and Diathane M-45 @ 3 kg/ha and by growing resistant varieties.
(iii) Stem rust (black rust) caused by Puccinia graminis tritici, which can be controlled by spraying the crop with Zineb @ 1.70 kg in 1,025 litres of water per hectare and seed treatment with Plantvax (0.25%) and by growing resistant varieties.
(iv) Loose smut, another common disease, caused by Ustilago tritici, which can be controlled by solar heat or hot-water treatment of seed, dry-seed treatment with Carboxin (0.25%), roguing out of smutted plants and by growing resistant varieties.
(v) Bunt caused by Tilletia foetida, which occurs in low- elevation hills of northern India, and that caused by T. caries, which occurs in higher and cooler parts of the hills, are controlled by treating the seed with Ceresan or Agrosan GN @ 2.5 g/kg and also by growing resistant varieties.
(vi) Karnal bunt caused by Neovossia indica is sometimes found in the sub-mountainous areas of the Punjab and can be controlled by growing resistant varieties.
(vii) Leaf blight, caused by Alternaria triticina, which has been reported from various states, particularly Bihar, West Bengal, Orissa, Maharashtra and Gujarat, can be controlled by growing resistant varieties 1 and by soaking seed in hot water (at 52°C) for 10 minutes and also by spraying of Ziram, Dithane M-45 or Dithane Z-78 (0.25%).
(viii) Flag smut caused by Urocystis tritici, which can be controlled by seed-dressing with Ceresan or Agrosan GN @ 1:500, practising crop rotation, roguing out diseased plants, applying irrigation immediately after sowing and by growing resistant varieties.
(ix) Powdery mildew, which is caused by Erysiphe graminis, is common in lower Kangra Valley and in the southern hills and is controlled by dusting powdered sulphur @ 15-20 kg/ha, by soil treatment with Benomyl (600- T000g/100 kg) and by growing resistant varieties.
(x) Earcockle caused by the nematode, Anquina tritici, is common in Punjab and UP, and is controlled by using clean seed (free from galls) for sowing, removing galls by sieving or by floating in 20% salt solution and also by roguing out diseased plants.
In contrast to fungal diseases, there is till now no serious insect pest of wheat in India.
Insect Pests of Wheat Crop:
Some of the common insect pests are:
(i) White ants (Odontotermes obesus, Microtermes obesi), which are found in some arid areas and can be controlled by mixing 5% Aldrin or Chlordane dust with the soil at the time of sowing or during land preparation.
(ii) Gujhia weevil (Tanymecus indicus), which is controlled by ploughing the field in summer to expose and kill the pupae, by mixing 5% Aldrin or Heptachlor with soil, and, in case of for adults, by dusting 5% BHC.
(iii) Stem-borer (Sesamia inferens), which can be controlled by dusting 5% BHC; or spraying 0.05 Endosulfan and by removing dead hearts in the initial stage.
(iv) Wheat aphids (Schizaphis graminum), which is controlled by dusting 5% BHC or spraying 0.02% Phosphamidon or 0.03% Dimethoate or Diazinon.
(v) Cut worms (Agrotis ipsilon, A. flammatra), which can be controlled by dusting 10% BHC on the soil around the plants.