Cereal crops are a group of agricultural crops including the Poaceae or Gramineae family and buckwheat in the Polygonaceae family. Cereal crops include:
- wheat (winter and spring),
- rye (winter and spring),
- triticale,
- barley (winter and spring),
- oats
- corn,
- millet
- sorghum,
- rice.
Cereal crops are divided into:
- Group I – cereal crops of northern origin with a long day in summer: wheat, rye, triticale, barley and oats;
- Group II – cereal crops of southern origin with a short day in summer: corn, millet, sorghum, buckwheat and rice, sometimes also include chumiza (Italian millet), paisa (Japanese millet), African millet.
Group I crops include spring varieties, winter varieties, and double-crops; Group II crops include only spring varieties.
Winter cereals are crops that require low temperatures of -1 to +10° C for 20 to 60 days to pass the stage of spring development. They are sown in autumn, 50-60 days before the onset of stable frosts, the harvest is obtained the following year. When sown in the spring, they most often bush and do not form a stem and ear.
Spring cereals require higher temperatures of +5 to 20°C for 7 to 20 days to pass through the stage of spring break. They are sown in spring and harvested the same year.
Doubles go through the stage of germination at +3-15 ° C. For southern areas, varieties that grow and develop well and yield both spring and autumn sowing.
Classification of crops into winter, spring and double crops is relative, but in practical terms is of great importance, as it allows to distribute the intensity of work in the spring period and during harvesting.
“… there are questions which always excite a lively interest, for which there is no fashion. Such is the question of bread.”
K.A. Timiryazev
- Cereal crops (Русская версия)
Economic importance
Cereals are the world’s food staple, accounting for about half of the world’s cultivated land. In terms of their food value, they can be arranged in the sequence: wheat, rice, corn, millet, sorghum, barley, oats, rye.
Of the 15 major crops used for food, half are cereal crops.
At the end of XX century cultivated area of cereals in the world was about 700 mln ha, i.e. 70% of all sown area, gross output – 2100 mln tons, average yield – 3.0 t/ha. In 2001-2005 Russia had 43.7 mln ha under crops; gross output was 78.1 mln tonnes, and average yield was 1.9 tonnes/ha.
Grain is valuable as food for humans, fodder for livestock and raw material for the processing industry. By comparison, it takes 6-7 times more farmland to produce a unit of energy contained in meat than it does to produce the same amount of energy in grain products. Bran, in the form of green mass, silage, hay, haylage and wastes of grain processing, chaff and straw are used as feed in animal husbandry. Straw is used as an organic fertilizer and bedding for livestock and for the production of paper. Grain is used in the milling, baking, food and other industries.
Due to their genetic diversity and broad plasticity to different soil and climatic conditions, cereal crops are grown in a variety of geographical locations. Modern productive varieties retained the ability to respond to the factors of intensification of agriculture: fertilizers, tillage, irrigation. Cereal crops are characterized by a high multiplication factor of 1 : 20 with relatively low requirement for cultivation technology.
Over the years, the gross yield of grain in the USSR has increased mainly due to the expansion of sown areas. In 1940 the sown area under grain crops was 110.7 million hectares, while in 1984 – In 1940 the area under crops was 110.7 million hectares while in 1984 it was 119.6 million hectares. Cultivated areas expanded in almost all years from 1940 to 1984 but especially in 1954-1958 during development of virgin and fallow lands. Grain crops also expanded as a result of the reduction of bare fallow areas.
Table. Sown areas of cereal crops in the USSR[1]Crop production/P.P. Vavilov, V.V. Gritsenko, V.S. Kuznetsov et al. Gritsenko, V.S. Kuznetsov et al; Edited by P.P. Vavilov. - M.: Agropromizdat, 1986. - 512 p.: ill. - (Textbook and textbooks for … Continue reading
| Crop | |||||
|---|---|---|---|---|---|
| Cereals | |||||
| Including: | |||||
| - winter wheat | |||||
| - spring wheat | |||||
| - winter rye | |||||
| - corn on a kernel | |||||
| - barley | |||||
| - oats | |||||
| - millet | |||||
| - buckwheat | |||||
| - rice | |||||
| - leguminous | |||||
| The entire sown area | |||||
In the same period the sown areas of winter and spring wheat, especially high-yield intensive varieties, barley, rice and leguminous crops increased. Sowings of winter rye, corn, oats, millet, and buckwheat decreased slightly.
From 1940 to 1976-1980, grain yields in the USSR increased from 0.86 to 1.60 t/ra. Yield increases were noted for all cereal crops except buckwheat.
Table. Cereal crops yield (100 kg/ha)[2]Plant breeding/P.P. Vavilov, V.V. Gritsenko, V.S. Kuznetsov et al; Edited by P.P. Vavilov. - M.: Agropromizdat, 1986. - 512 p.: ill. - (Textbook and textbooks for higher education institutions).
| Crop | |||||||
|---|---|---|---|---|---|---|---|
| Cereals | |||||||
| Winter wheat | |||||||
| Winter rye | |||||||
| Spring wheat | |||||||
| Barley | |||||||
| Oats | |||||||
| Corn on grain | |||||||
| Millet | |||||||
| Rice | |||||||
| Buckwheat | |||||||
| Leguminous | |||||||
The gross harvest averaged 106.0 and 104.3 million tons in 1976-1980 and 1986-1990, respectively. In 1992 it was 106.9 million tons, with a crop area of 61.9 million hectares. However, the reforms initiated in Russia in 1991 led to a sharp decline in grain production. In 1994-1998 the average gross output was 70 million tons, in 1998 it was less than 48 million tons.
The advantage of cereal crops is their ability to be stored from harvest to harvest, which makes it possible to create reserves of grain for several years. Grain is convenient for transportation, and the methods of processing is relatively simple.
The main direction of cereal farming development nowadays is to increase crop yields with limited opportunities to expand the areas under crops.
Botanical description
Root system
The root system is fibrous. Primary (germinating) roots are formed during seed germination. Cereals of group I have up to 3-8 of them, for group II – 1. For example, winter wheat has 3, spring wheat 5, rye 4, oats 3-4, barley 5-8. Germ roots function throughout plant life, and their importance increases in drought conditions.
Secondary (nodular, adventitious) roots are formed 12-18 days after seedlings emerge from underground stem nodes. Optimal soil humidity is important for their rapid growth and development; if the upper soil layer dries out, their growth is very slowed down or suspended completely. A good yield of grain crops is possible only with well-developed nodular roots.
Secondary roots are of great importance for plants. For example, when spring wheat develops only with primary roots, the yield is 65% of the yield of plants with developed primary and secondary root systems.
High-growing cereal crops, such as corn and sorghum, may form supporting (aerial) roots from stem nodes located close to the soil surface. They contribute to the resistance of plants to lodging and participate in the supply of nutrients.
The depth of penetration of the root system of grain crops can reach 150-200 cm, but the main mass (75-90%) is located in the arable soil layer (0-30 cm). Roots account for about 20-25% of the total mass of dry matter. Corn, winter wheat and rye have the most powerful root system.
The structure of the root system and the nature of its development are determined by the plant species and variety. Winter rye, oats, and corn have the most powerful root system. The roots not only absorb water and dissolved nutrients, but also form organic substances such as organophosphorus compounds, amino acids, amides, alkaloids.
Stem
The stem of cereal crops is represented by a cylindrical straw, hollow or filled with parenchyma (sorghum, maize). More often it consists of 5-7 internodes separated by special septa – nodes, in corn and sorghum – 8-16. The number of internodes in long-stemmed corn varieties may reach 25. Their number corresponds to the number of leaves.
Stem growth is called inset or intercalary, as it occurs due to lengthening of all internodes. And each new internode grows faster than the previous one. The upper internode is much longer than the lower one, and reaches its maximum length during flowering. The leaves exhibit an S-shaped growth curve, which is slower at the beginning and end of vegetation, but intensive in the middle of vegetation, during the phases of tubing formation, ear emergence and flowering.
Lodging resistance depends on the thickness and strength of internodes. The stem is most thick in the middle part and least thick in the upper part. Its strength depends on the composition of the mechanical tissue. It has the ability to form lateral shoots from underground stem nodes.
When secondary roots and lateral shoots are formed from underground stem nodes, the tillering phase of cereal crops begins.
Leaf
The leaf of cereal crops is linear, consisting of a leaf sheath and a leaf lamina; at their junction, there is a ligula, a thin colorless film, and lugs, which is a systematic feature in identifying cereals of the first group. The uvula adheres tightly to the stem and does not allow water to penetrate into the leaf sheath.
At the base of the leaf sheath, linear lugs, or horns, auricula, are formed on both sides, encompassing the stem. The structure of the uvula and auricles for most cereal plants is different in the early phases of growth. For example, the uvula in wheat, rye, and barley is short, often with cilia; in barley it is very large, without cilia, semilunar in shape; in rye it is short without cilia, falling off early; in oats the uvula is absent.
The number of leaves and their size differ between different grains and varieties.
Inflorescence
The inflorescence of cereal crops is represented by two types:
- complex spike (wheat, rye, triticale, and barley);
- panicle (oats, millet, sorghum, and rice).
Unlike other crops, one corn plant produces two inflorescences – the panicle with male flowers in the upper part of the stem, while the cobs with female flowers in the axils of the leaves.
Spike
The spike is an extension of the stem, including a segmented spike shaft and the spikelets located on its ledges. The wide side of the stem is called the front side and the narrow side is called the lateral side. One spikelet, as in wheat, rye, triticale, or three (barley) may be placed on each ledge. Spikelet scales differ from crop to crop.
The stem of the ear of wheat is cranked, with one spikelet on each segment, usually consisting of two spikelet scales and one or more flowers; the stem ends in an apex spikelet. In rye, the spike shaft is pubescent; each spikelet has one spikelet with its broad side facing the shaft; one spikelet contains two flowers. The barley ear differs from wheat and rye ears in having three one-flowered spikelets located on each stem of the ear shaft.
For multi-row barley, grain formation in each of the three spikelets is characteristic; for double-row barley, only in the middle spikelet.
Panicle
The panicle consists of a central axis with nodes and internodes. Lateral branches are formed at the nodes, which also branch, forming branches of several orders. At the ends of each branch there is a spikelet: multi-flowered in oats and single-flowered in rice, millet and sorghum.
Flower
The flower of cereal crops has two flower scales, the lower (outer) and the upper (inner). The outer flower scale in spinous forms has an awn. The upper one is thinner and flatter. The ovary with a reverse ovary and two pinnate stigmas and three stamens (six in rice) are located between the flower scales. At the base of the flower scales, there are two thin films, the lodicula, which, swollen during flowering, cause the flower to open.
Wheat flowers are wide, with a longitudinal keel; rye flowers are very narrow; barley flowers are narrow, almost linear; oat flowers are wide, with many convex longitudinal veins.
Fruit
The fruit is represented by a single seed pod (caryopsis), which is usually called a grain. It contains a single seed covered with a seed coat formed from the two shells of the ovary and the fruit coat formed from the ovary. Grain consists of germ, endosperm and fused with them seed and fruit shells.
Grain of filmy cereals is covered with flower scales, which may fuse with it, as for example, in barley, or just tightly envelop it, as in oats, millet, sorghum, rice. The germ accounts for 2-12% of the mass of the grain. The germ consists of a germinal root and stem, a kidney, and a shield, representing the modified seedpod.
Grains of holo-grain wheat and rye are easily separated from the scales. The floral scales of millet, chumisa and rice fit tightly around the grain; in filmy barley, they may fuse with the grain.
The endosperm makes up 70-85% of the weight of the grain. Its tissues consist of parenchyma cells filled with starchy grains, between which there is a protein substance. The peripheral part of the endosperm, called the aleurone layer, does not contain starch; it consists of large cells filled with soluble protein matter. The aleurone layer contains enzymes and biologically active substances that regulate the process of grain germination.
The germ is located at the base of the grain on the convex side. It consists of a shield connecting it to the endosperm, a kidney covered with rudimentary leaves, a primary stem, and a spine. The germ accounts for 1.5-2.5% of the grain mass for wheat, rye, and barley, 2-3.5% for oats, and 10-14% for corn.
Fruit and seed shells account for 5-7% of the total grain mass.
Chemical composition of grain
Grain contains all the necessary nutrients for humans and animals, the ratio of protein to carbohydrates is 1: 5-6.
The chemical composition varies greatly depending on the crop and variety, soil and climatic conditions and agricultural technology.
Table. Chemical composition of cereal grains (in %)[3] Plant breeding/P.P. Vavilov, V.V. Gritsenko, V.S. Kuznetsov et al; Edited by P.P. Vavilov. - M.: Agropromizdat, 1986. - 512 p.: ill. - (Textbook and textbooks for higher education institutions).
| Crop | |||||
|---|---|---|---|---|---|
| Soft wheat | |||||
| Durum wheat | |||||
| Rye | |||||
| Barley | |||||
| Oats | |||||
| Corn | |||||
| Rice | |||||
| Millet | |||||
| Buckwheat |
Proteins
According to the reference data, the protein content of cereals may vary from 6.7 percent for rice to 12.9 percent for wheat; the fat content may vary from 1.7 to 1.8 percent for rye and wheat to 5.3 to 6.9 percent for oats and corn; the carbohydrate content may vary from 59.7 percent for oats to 69.6 percent for rye. Nitrogen-free extractive substances such as starch, sugar, etc., which are mainly found in the endosperm, account for the bulk of the grain.
Simple proteins are called proteins; complex proteins are called proteids. Simple proteins are represented by groups of albumin (water-soluble), globulin (salt-soluble), glutelin (soluble in acids and alkalis), prolamin or gliadin (soluble in 70-80% ethyl alcohol). The last two groups are the most valuable, with an optimum ratio for baking of about 1:1.
Durum wheat varieties have the greatest amount of protein. Grain protein content for all grains increases when their crops are grown from north to south and west to east. Grain quality is influenced by the dryness of the climate and the nitrogen content of the soil. For example, according to the long-term data of the Central Chemical Laboratory of the State Variety Testing Commission, the amount of protein in the grain of spring wheat grown in the North-Western regions of the country is 12.6%, while in areas of Northern Kazakhstan – 17.3%.
The protein content in grain is influenced by the applied agricultural techniques: for example, the introduction of organic and mineral fertilizers, placement on the best predecessors. Grain of wheat harvested in the period of waxing ripeness contains more protein than those harvested in the period of full ripeness.
Protein quality depends on the composition of amino acids, especially valine, lysine, tryptophan.
Gluten
Flour quality is characterized by the content of gluten, which is a clump of water insoluble protein (gluten) substances remaining after washing the dough of starch, fiber and other substances. Gluten contains some fat, starch and ash elements. The highest quality gluten is located in the center of the grain, its quality decreases sharply during germination of the grain, frost damage or pests.
Raw gluten content varies in wheat from 16 to 50%, in rye from 3.1 to 9.5%, and in barley from 2 to 19%. The quality and yield of gluten depends on external conditions. For example, during dry and hot weather the gluten content is higher, while damage to the grain by the pest turtle, leads to a sharp decrease in content. Quality gluten is capable of stretching long without breaking and resisting stretching.
Wheat gluten is the most valuable, which is why wheat bread has a higher porosity and digestibility. Rye gluten is less elastic and tensile.
Carbohydrates
Among the carbohydrates, starch accounts for the greatest amount, 80% of which of the weight of all carbohydrates is contained in the endosperm. The remainder is sugar, which is mainly contained in the germ (about 1.5% of the weight of the grain). Carbohydrates are concentrated in the central part of the grain.
Depending on the nature of the starch grains and their location in the endosperm cells, the grain is divided into floury and vitreous grains. In the endosperm of a floury grain, the spaces between the large starch grains are filled with small ones with thin protein interlayers. In the vitreous grain, small starch grains are almost absent; the interlayers of protein are thicker and fill all the gaps between the large grains.
Grain starch content increases as crops move from east to west and from south to north, that is, in the opposite direction to the change in protein content.
Fiber is a high-molecular-weight polysaccharide found in cell walls, grain shells, and scales in filmy crops. The content of fiber is higher in small grains than in large ones.
Fats
The fats content in the grain varies from 2 to 6%. The content of fats and lipids is highly irregular in grain, they are mainly concentrated in the germ, in wheat about 14%, in rye and barley 13.4%, in millet 20%, in oats up to 26%, in corn up to 40%.
High fat content in flour leads to its rancidity. To improve the quality of corn flour, the germ, which is used to produce oil, is removed before milling.
Ash substances
In filmy cereals ash is mainly contained in the films, in holo-grain cereals – in the fruit shell. In complex milling, most of the ash is separated with bran.
Ash substances are represented by compounds of phosphorus (up to 50% of the total weight of ash substances), calcium (up to 2.8%), potassium (up to 30%), sulfur, silicon, magnesium (up to 12%), etc. Their greatest amount is in the shell and scales.
Enzymes and vitamins
Grains also contain enzymes involved in life processes, such as amylase (breaks down polysaccharides and disaccharides), protease, maltase, cystase, diastase, lipase (breaks down fats), and peroxidase.
The grain contains vitamins B1, B2, B6, PP, E, A.
Water
Water involved in physiological processes is found in grains in the form of:
- chemically bound, i.e. included in the molecules of substances in certain ratios, this water is characterized by constancy and inertness;
- physically-chemically-bound water, which is part of the composition of the grain in various ratios; it can be in the form of adsorption-bound, osmotically absorbed or structural water;
- mechanically bound, or free; the amount can vary greatly; easily lost in drying.
Grain is put into storage with a moisture content not exceeding 14-15%, that is, in air-dry condition.
Growth phases (phenological phases)
During the growing season, cereal crops undergo phenological phases, distinguished by the appearance of new organs and external morphological signs.
The following phenological phases are distinguished:
- sprouting, or germination (sometimes considered separately),
- tillering,
- emergence into a tube (tubing),
- stemming (sometimes not included),
- ear emergence (or formation of a panicle),
- flowering,
- ripening.
A phase is considered to occur on the day when at least 10% of the plants enter a new phase. The full phase occurs when 75% of plants have signs.
Germination
Seed germination is a complex biological process involving several physiological and biochemical transformations and ends with the appearance of the first green leaf on the soil surface. A prerequisite for germination is the presence of water, heat and air. The germ absorbs water faster than the endosperm, which leads to uneven swelling of the grain and rupture of the shell.
Depending on grain weight (in the air-dry state) different cultures need water: oats 60-76%, wheat 47-48%, rye 56-65%, barley 48-57%, corn 37-44%, millet, sorghum, chumisa 25-38%. For comparison, legume seeds need 100-125% of water of grain weight for swelling. Larger grains with dense shells and high protein and fat content need more time to swell.
Water absorption rate depends on temperature, soil solution concentration, structure and grain size. The optimum temperature during the swelling period for grains is 10-21°C. Higher salt concentration slows down germination. Vitreous or coarse grains are slower to absorb water than floury or fine grains. For this reason, the flatter the seed, the more uniform the germination. Filmy grains are slower to swell than holo-grain grains.
In the swollen grain, hydrolysis of the stored nutrients of the endosperm takes place under the action of enzymes. Special enzymes cytase and amylase break down starch and hemicellulose of endosperm into simple carbohydrates dextrin and maltose. The enzyme invertase converts sugars into glucose and fructose, which are used by the germinating plant for respiration and cell growth. The enzyme protease breaks proteins down to amino acids and ammonia; lipase breaks fats down to fatty acids and glycerol.
During germination of the grain, stored nutrients are broken down to form compounds that form the organs of the plant.
D.N. Pryanishnikov established that endosperm proteins form amino acids and small amounts of asparagine and glutamine during enzymatic cleavage. These substances react with the products of carbohydrate breakdown, thus serving to form new proteins in the growing embryo as well.
Germination begins with the growth of the germinal roots and then the stem. Optimal temperature of germ emergence and initial growth at usual sowing dates for Group I loaves is 6-12°C, Group II – 15-22°C. The minimum germination temperature for Group I is 1-2°C, Group II – 8-10°C. Physiological optimums – for Group I – 20 °C, Group II – 25-27 °C. Higher temperature leads to slower germination, and when it reaches a certain limit, it leads to a halt in growth. Extreme temperatures above 30-35 °C are destructive, and below 1-2 °C lead to halted germination.
Uniformity of germination is negatively affected by lack of air and excessive moisture. As the seedlings develop, the need for oxygen increases. For this reason, deep embedding of seeds is undesirable, especially on heavy soils, as well as the formation of soil crust.
Sprouts
During the first days of life of cereal crops there is an intensive development of primary (germinal) roots. Then the stem begins to develop. In holo-grain varieties, the stem appears near the scutellum, in filmy varieties – under the flower scales and comes out of the upper end of the grain.
Sprouts emerge on the soil surface in the form of stem shoots covered with a transparent leaf, the coleoptile. The coleoptile protects the stem and the first leaf from mechanical damage as it germinates from the soil. As soon as the leaf reaches its normal size, the coleoptile dies off.
The first leaf completes growth 6 to 11 days after sprouting. Then, about a week after the first leaf unfolds, the second leaf appears in its axils, followed by the third and fourth at the same intervals. At the same time, the root system develops. By the time of formation of the 3-4-th leaf germinal roots are well branched and penetrate to a depth of 30-35 cm. They reach 40-50 cm in the tillering phase and 60-90 cm at stemming. Good soil moisture promotes growth.
Wheat sprouts are usually green; spring soft wheat sprouts are glaucous-green, rye sprouts are purplish-brown, oats sprouts are light green, and barley sprouts are glaucous-smoky. The color of sprouts of grains of the second group is green or pale green.
The appearance of sprouts depends on many factors: the characteristics of the crop, humidity, temperature, particle size and density of the soil, sowing depth, and the energy of germination of the seeds. Rapid emergence of sprouts (in 4-6 days) is favored by warm and humid weather, while a sharp cold snap inhibits this process.
Tillering
In the tillering phase, adventitious (nodal) roots are formed from the underground nodes of the stem, and then lateral shoots appear. Most often, they are formed from the uppermost node, called tillering node, located at the depth of 1-3 cm from the soil surface. The tillering node is a complex formation consisting of close nodes from which secondary (adventitious) roots and stems (lateral shoots) are formed. A deeper tillering node contributes to the resistance of plants to lodging and resistance to adverse conditions.
The tillering consists in the fact that the bud located at the base of the first leaf enlarges, pushes it away, and forms a lateral shoot. Then, new buds are formed in the axils of lower leaves of lateral shoots, capable of forming lateral shoots of the second, third, etc. orders.
At the same time, secondary roots are formed. Unlike germ roots, which are formed from the seed and penetrate to a greater depth, secondary roots are formed from the tillering node and are located mainly in the surface layer.
Good development of secondary roots is favored by sufficient soil moisture and availability of nutrients, especially phosphorus. If the top layer dries out, secondary stems and roots are not formed. Under these conditions, only the main stem and the primary root system are laid, which sharply reduces the yield.
The first underground node is formed on the 5th-7th day after sprouting for most Group I loaves, or simultaneously with them for Group II loaves and oats.
The depth of the underground tillering node is influenced by light. Lack of light leads to its shallow occurrence. The depth is also affected by the sowing depth, variety, soil type, and temperature. For example, when the temperature is low, the tillering node is deeper; durum wheat varieties also form the tillering node deeper than soft wheat. A deeper tillering node in winter crops protects them from adverse conditions during the winter-spring period.
In cereal plants the tiller node is a very important organ since the formation of the aboveground mass and root system, drought tolerance, winter hardiness, etc. depend on its normal development. Even partial damage to it may lead to stunting of plant growth, and its dying off may lead to its complete death.
Total bushiness (tillering energy) is the number of stems (shoots) developing from one plant. Under field conditions, winter crops have 5 to 8 stems, spring crops have 2-3, and under favorable conditions the number may reach 5 to 10 or more.
Productive bushiness is the number of stems per plant that produce grain. If side shoots are formed too late, they have no time to form and mature into grain. Shoots with unripe grains are called underbush, while unthickened ones are called undergrowth (the terms are rarely used, and there is no exact translation). The higher the productive bushiness, the more grains per plant, but the highest yield per unit area is obtained with a low bushiness and optimal density of stems.
Under optimal soil and climatic conditions, the maximum yield of grain crops is achieved with a total bushiness of 5-8 shoots and productive 2-3. Winter cereals usually have 3-6 productive stems, barley and oats 2-3, spring wheat 1, sometimes 2, corn 1, rice, millet, and sorghum 2-5. Large ears and grains are formed on productive stems.
According to V.N. Stepanov, the dynamics of development of tillering shoots and knot roots is different in grain crops. For example, in winter and spring rye and oats, tillering and rooting occur simultaneously, during the formation of 3-4 leaves. In barley, winter and spring wheat, tillering shoots are formed during the third leaf formation stage, while rooting occurs when 4-5 leaves appear. In pearl millet, tillering occurs when 5-6 leaves appear; in corn, 6-7 leaves; in sorghum, 7-8 leaves. Nodular roots in these crops are formed when 3-4 leaves appear. Earlier terms of root system appearance in comparison with the beginning of tillering stage determine the ability of crops to better tolerate moisture deficit (except corn) in the first and subsequent periods.
All future plant parts are located in the tillering node, and at the same time nutrient reserves are concentrated in it. The dying off of the tiller node in all cases leads to the death of the plant.
The beginning of tillering of different crops is observed at different times, e.g. for Group I when 3-4 leaves are formed, for Group II when 5-8 leaves are formed.
The size of the yield is determined primarily by the capacity of the root system and the above-ground part. According to studies by A.L. Kursanov et al. using the method of radioactive isotopes, showed the ability of roots, in addition to providing plants with water and minerals, to synthesize amino acids and nucleoproteins.
The tillering energy and bushiness depend on such factors as water-air, heat, food and light regimes, plant type and variety, seed quality, sowing period, seeding rate, etc. The tillering of cereal crops of the first group can take place at about 5 °C, but the tillering energy is weak. The optimum temperature for tillering is 10-15 °C. Higher temperatures result in a shorter tillering phase, and fewer shoots are produced.
In winter crops, when optimal timing and conditions are observed, tillering occurs in autumn.
The productive importance of the tillering phase is ambiguous. Thus, according to P.N. Konstantinov, A.I. Nosatovsky, P.P. Lukyanenko and others, the tillering phase is undesirable, especially in arid areas. They believe that a lot of water and nutrients are spent on the formation of secondary stems, which causes poor nutrition of the main stem, and the grain yield of secondary stems is insufficient to compensate for the lack of grain from the main stem. Therefore, they called 1-2-stem plants the optimal type of spring crops for the conditions of arid regions.
The opposite point of view was held by V.R. Williams, V.E. Pisarev, S.A. Muravyov and others. They believed that due to good tillering, a large leaf mass develops, which contributes to the production of more organic matter for grain formation. Under favorable conditions, lateral stems can produce 30-50% of the grain yield. However, under conditions of sufficient moisture, strong tillering can lead to negative results.
Thickened crops are more prone to lodging, photosynthesis conditions and grain filling worsen, and harvesting losses increase. More often, the average number of productive stems per m2 is 350-400, providing a yield of 2-3 t/ha. In some cases, it is possible to increase up to 700-800 per m2.
Tubing
In the tillering phase of crops, the stem (straw) begins to form. The internodes, initially in the form of transverse scars at the base of the rudimentary spike or panicle, are elongated. The moment when a stem knot is palpable inside the leaf sheath of the main stem at a height of 5 cm from the soil surface is considered to be the beginning of tube formation (tubing).
Sometimes, simple lengthening of the leaf sheath is mistakenly considered to be the phase of emergence into the tube, e.g., this often happens in autumn in overgrown winter crops. First, the lower internode is lengthened, then the second, third, etc., with each new internode overtaking the previous one in growth. Such stem (straw) formation is commonly referred to as inset, or intercalary.
Ear emergence (formation of the panicle)
The ear (or panicle) and spikelets are deposited in the tillering phase. The ear emergence (earing) phase is when 1/3 to half of the ear (panicle) emerges from the sheath of the upper (flag leaf) of the main stem. The formation of panicles in corn – sultanas – occurs earlier in comparison with female inflorescences – cobs.
Further differentiation of the ear (panicle) begins at temperatures above +15°C. At the stage from emergence of the tube to ear emergence (formation of the panicle), cereal crops have higher requirements for light, heat, soil moisture and nutrients, since this period is accompanied by intense growth and formation of the ear (panicle).
The size of the ear is strongly influenced by the ratio of nutrients. Excess nitrogen during this period leads to a delay of several days of cone formation and the formation of a large number of spikelets. An excess of phosphorus leads to an accelerated formation of spikelets and a reduction in their number.
Flowering
Flowering – fertilization. In all crops, except winter rye, flowering begins soon after earing (panicle formation). Barley blossoms before full earing, while rye blossoms 8 to 10 days after.
Cereal flowering is divided into self-pollinating, for example, in barley, wheat, oats, millet, and rice, and cross-pollinating in rye, corn, and sorghum. In self-pollinating ones, the anthers mature while the flower is still closed, so pollen usually falls on the stigmas of the same flower before it opens. Barley is one of the strictest self-pollinators because it pollinates during ear emergence or even earlier (closed flowering).
The ear usually flowers for 3 to 4 days and the panicle for 6 to 7 days.
When the flowering phase begins, the development of stems, leaves, and ears stops. The largest increase in wet weight occurs during ear emergence, while dry weight increases during wax maturity of the grain.
Flowering in wheat can occur with both closed and open scales, depending on external conditions. Closed scales are observed under unfavorable conditions (rainy or cloudy weather), with only self-pollination possible. In hot and dry weather, it is open.
With a lack of moisture and other unfavorable conditions, barley flowering may occur in the leaf sheath. At this time, flower scales open and ripe anthers and stigmas appear. In rye and wheat, flowering begins in the middle part of the ear. In millet, sorghum and oats, the process begins at the top of the spikelets, gradually passing to the base of the panicles.
Flowering responds quickly to unfavorable weather conditions, such as a sudden rise or fall in temperature, drought, rainfall and strong winds. In this case, incomplete pollination occurs, resulting in partial graining of ears, panicles, cobs, the so-called through-graining.
Ripening
Ripening – development of ovary and grain formation begins after flowering and fertilization. Early sowing, increased density of stems, application of phosphorus-potassium fertilizers, warm, clear and dry weather contribute to acceleration of ripening. In contrast, wet weather or irrigation and thinly spaced crops slow the ripening process.
High temperature, air and soil drought during the ripening period leads to “fuse” or “capture” of grain: the ripening decreases, the grain is formed puny and wrinkled, which sharply reduces the yield and its quality. Very rainy and warm weather leads to “draining” of grain due to hydrolysis of starch and washout of dissolved substances by water.
A certain sum of active temperatures is necessary for normal maturation of cereal crops. If in rainy weather the harvesting is greatly delayed, it can lead to sprouting of grain in ears at the root and in windrows. In the north of European Russia and in Siberia with rainy and cold weather, harvesting is often delayed, which can lead to frost damage of unripe grain and a sharp decrease in the yield of “frost-bitten” grain and its quality.
N.N. Kuleshov suggests dividing the process of grain formation into three stages:
- formation;
- filling;
- ripening.
Seed formation is the period from grain formation to establishment of the final length. A seed can produce a weak sprout. The weight of 1,000 seeds is 1 g. The duration of formation is 7-9 days or more.
Formation is the period from grain formation to establishment of the final length. Seeds have a high free water content and a low dry matter content. Weight of 1000 grains is 8-12 g.
Filling is the period from the beginning of starch accumulation in the endosperm to its cessation. Humidity decreases to 37-40%, the duration is 20-25 days.
The filling period is divided into four stages:
- The watery phase is the beginning of endosperm cell formation. Dry matter is 2-3% of its maximum quantity, the duration of the phase is 6 days.
- Pre-milk phase – the content of the grain of watery consistency with a milky hue. The content of dry matter is 10%. Duration of the phase is 6-7 days.
- Milk state phase – grain contains milky white liquid. Dry matter is accumulated 50% of the weight of the mature grain. The duration of the phase is 7-15 days.
- Doughy state phase: endosperm acquires dough-like consistency, 85-90% dry matter is accumulated, duration of the phase is 4-5 days.
Grain ripening begins with the cessation of plastic substances. Grain moisture at this time decreases to 8-12% and becomes suitable for technical use, but seed development is not yet complete.
The filling period is sometimes called the milky ripeness phase, when the plants are still green, the stem and leaves begin to turn yellow at the bottom, the lowest leaves die off, and the moisture content of the grain varies from 60 to 40%.
The ripening period is divided into two phases:
- The phase of waxy ripeness – the endosperm is waxy, elastic, easy to cut with the nail, the shells are yellow. Humidity decreases to 30% (22-40%). The duration of the phase is 3-6 days, germ growth and accumulation of plastic substances stops. Plants in this phase are yellow, except for 2-3 top catches of stem and part of the inflorescence.
- The phase of hard ripeness – endosperm hard, on a break floury or vitreous, the shell dense, leathery, color typical, moisture content 8-22% (depending on the zone). The duration of the phase is 3-5 days.
In the phase of hard ripeness, complex biochemical processes take place, after which the property of the seed – germination – appears. Because of the last stage, two additional periods are distinguished: postharvest ripening and full ripeness.
During postharvest ripening synthesis of high-molecular protein compounds is completed, free fatty acids are transformed into fats, carbohydrate molecules are enlarged, and respiration stops. At the beginning of this phase, seed germination is low; by the end, it is normal. The duration depends on the peculiarities of the crop and external conditions, and varies from a few days to several months.
Full ripeness occurs when the seeds are ready to begin a new life cycle of the plant, and germination reaches its maximum value. Plants at this stage are yellow, the leaves die off, and the grain is hard and reduced in size.
Harvesting is carried out at the wax ripeness stage by separate harvesting, and at the full ripeness stage by direct harvesting.
In some regions, such as Northern Kazakhstan, Siberia, etc., in some years the ripening of cereal crops is delayed, the plants are damaged by frost, giving frost-bitten grain and leading to lower yields and quality deterioration. Therefore, two-phase harvesting is used in these regions – in the first half of the phase of wax ripeness. Being in swaths, the grain is less damaged by frosts, and it continues to receive plastic substances as long as the stems and leaves contain water.
In southeastern Russia, premature ripeness of grain occurs due to dry winds, which cause the growth and accumulation of plastic substances to be suspended earlier. Grain becomes wrinkled, puny, and its flour-milling and baking properties deteriorate. Grain stubbornness leads to a decrease in yields. The main remedy against dry winds is expansion of protective field afforestation, accumulation of moisture in the soil, use of early maturing varieties and harvesting in a short time.
Life cycle of cereal crops (organogenesis)
Organogenesis – the stages of plant life cycle. Introduction of high and intensive technologies of crops cultivation requires detailed control of peculiarities of production processes of different species and varieties of cereal crops during the passage of the stages of the life cycle.
In 1962, 12 stages of organogenesis for cereals and other crops were developed under the guidance of Kuperman F.M. Each stage is characterized by a certain state of growth cone and formation of new organs or changes in their development. Thus the whole life cycle of an annual plant is divided into three periods:
- embryonic and juvenile (I-IV stages);
- maturity and reproduction (V-VIII stages);
- old age (stages IX-XII).
The following 12 stages of organogenesis of cereal crops have been experimentally established:
- Formation of the primary growth cone of the stem;
- Intensive differentiation into rudimentary nodes, internodes and leaves;
- Lengthening of growth cone with formation of segments of ear (panicle);
- Setting and formation of spikelet tubercles;
- Flower tubercles formation and differentiation;
- Formation of pollen grains and pistil, growth of covering flower organs;
- Intensive growth in length of all spikelet (panicle) organs;
- Completion of ear (panicle) and flower formation;
- Flowering and fertilization, zygote formation;
- Growth of grain and seed organs;
- Accumulation of nutrients in grain, the beginning falls on the phase of milky ripeness, lasts up to waxing;
- Conversion of nutrients into storage, the ripening of the seed.
Visually, these stages are manifested through phases. The first two phases in winter cereals at the optimal time of sowing are completed in autumn, the next ones begin in spring with the renewal of vegetation.
A detailed scale for characterizing the productive processes of cereals and other crops was developed in Western Europe in the second half of the XX century. The international code BBCH allows the use of modern computers in experimental agronomy (Spaar et al.).
Table. Growth and development of cereal crops (code ВВСН)[4]V.V. Kolomeychenko. Crop production/textbook. - Moscow: Agrobiznescenter, 2007.
| 0 | Germination | 00 | Dry grain |
| 01 | The beginning of water absorption | ||
| 03 | End of water absorption | ||
| 05 | Emergence of the tip of the germinal root | ||
| 06 | Germinal root is stretched, root hairs and/or lateral roots are visible | ||
| 07 | Appearance of the tip of the germinal sheath (coleoptile) | ||
| 09 | Sprouting: coleoptile passes the surface of the soil, the leaf has reached its tip | ||
| 1 | Leaf development | 10 | The first leaf emerges from the coleoptile* |
| 11 | The first leaf is unfolded and the tip of the second leaf is shown | ||
| 12 | The second leaf is unfolded and the tip of the third is shown | ||
| 13 | The third leaf is unfolded and the tip of the fourth is shown** | ||
| 1... | Microphases of leaf deployment... | ||
| 19 | Nine or more leaves unfolded | ||
| 2 | Tillering*** | 20 | No tillering |
| 21 | The first shoot appears (beginning of tillering) | ||
| 22 | A second shoot appears | ||
| 23 | A third shoot appears | ||
| 2... | Microphases of the emergence of shoots... | ||
| 29 | End of tillering (maximum number of shoots reached) | ||
| 3 | Tubing | 30 | Beginning of tube emergence (main shoot and lateral shoots are strongly upward, begin to stretch). Spikelet distance from tillering node at least 1 cm |
| 31 | The first node is visible on the surface of the ground (distance of at least 1 cm) | ||
| 32 | The second node is visible (distance from the 1st node at least 2 cm) | ||
| 33 | The third node is visible (distance from the 2nd node at least 2 cm) | ||
| 34 | The fourth node is visible (distance from the 3rd node at least 2 cm) | ||
| 3... | Microphases of node formation... | ||
| 37 | Appearance of the last (flag) leaf, still curled up | ||
| 39 | The flag leaf is fully developed | ||
| 4 | Swelling of inflorescences (ears or panicles) | 41 | The leaf sheath of the flag leaf is elongated |
| 43 | The inflorescence (ear or panicle) inside the stem is shifted upwards, the leaf sheath of the flag leaf begins to swell | ||
| 45 | The leaf sheath of the flag leaf is swollen | ||
| 47 | The leaf sheath of the flag leaf opens | ||
| 49 | Awns appear above the leaf ligule of the flag leaf | ||
| 5 | Appearance of inflorescences (ears or panicles) | 51 | The beginning of the appearance of inflorescences. The top of the ear or panicle is visible |
| 52 | Appearance of 20% inflorescence | ||
| 53 | Appearance of 30% inflorescence | ||
| 54 | Appearance of 40% inflorescence | ||
| 55 | Appearance of half of the inflorescence | ||
| 56 | Appearance of 60% inflorescence | ||
| 57 | Appearance of 70% inflorescence | ||
| 58 | Appearance of 80% inflorescence | ||
| 59 | Appearance of the entire inflorescence, ear or panicle fully visible | ||
| 6 | Flowering | 61 | The beginning of flowering. The first stamens appear |
| 65 | Mid flowering (50% of mature stamens) | ||
| 69 | End of flowering | ||
| 7 | Grain formation | 71 | The first grains have reached half their final size, their content is watery |
| 73 | Early milk ripeness | ||
| 75 | Medium milky ripeness. All grains have reached their final size, still green with milky content | ||
| 77 | Late milky ripeness | ||
| 8 | Grain ripening | 83 | Early waxing ripeness |
| 85 | Soft waxy ripeness. Grain content is still soft, but dry (nail indentation straightens out) | ||
| 87 | Hard waxy ripeness (nail indentation does not straighten out) | ||
| 89 | Early full ripeness. Grain is hard | ||
| 9 | Die off | 92 | Late full ripeness. Grain is hard |
| 93 | Grain sits loosely in the ear during the day | ||
| 97 | The plant is completely dead. The straw is broken | ||
| 99 | Harvested grain harvest | ||
* The leaf is considered unfolded when the tip following it is visible.
** The tillering may occur from the 13th microphase, in which case proceed to the 21st microphase.
*** Emergence of the tube may start before the end of tillering, in which case go to the 30th microphase.
The international code was created thanks to the joint work of German specialists of companies producing chemical plant protection products: BASF AG, Bayer AG, Ciba-Geigy AG, Hoechst AG, hence the code name BBCH, which represents the first letters of the names of these companies.
Lodging of crops
Lodging (or lying) of crops can be caused by unfavorable conditions. The causes of lodging were established at the end of the last century by K.A. Timiryazev. He believed that the main one is the elongation of stem cells due to insufficient light, making their walls thinner. Lack of light is caused by strong tillering and excessive power of vegetative mass. The lower weakened internodes cannot support the weight of the above-ground mass, resulting in lodging of the plants.
If this happens early enough, the straw may be straightened due to the growth of leaf nodes; whereas in the case of lodging after lodging, there is no change in the crop.
The risk of lodging increases under irrigation due to the strong development of vegetative organs, increased moisture in the topsoil, and shallow tillering.
To prevent lodging, the depth of sowing is increased, so that the bush node is located deeper, and potash and phosphate fertilizers, which accelerate the development of stems and root system, are applied. Phosphorus-potassium fertilizers are applied before tillering. In contrast, early application of nitrogen fertilizers leads to increased tillering, delays development and reduces lodging resistance.
For lodging resistance of plants, narrow-row and cross-sowing methods are used, positioning rows from north to south.
The most important measure to prevent lodging is the use of resistant varieties. Also to prevent this phenomenon is the treatment of crops in the tillering phase with a plant growth regulator – tur (chlorcholine chloride), which prevents overgrowth and lodging of plants.
According to the data of the Department of Plant Industry of the Moscow Agricultural Academy, treatment of wheat with tur at a dose of 2-3 kg/ha leads to a decrease in the height of plants by 18-20%, while crop yield increases by 300-600 kg/ha. Late spring and weak plant development sharply reduces the effectiveness of the preparation.
To prevent the lodging of crops, special preparations – retardants – are used. They are well soluble in water and easily penetrate into plants. Under their influence, the lower internodes become shorter and thicker, and the height of the plants is reduced by 15-25 cm, which increases resistance to lodging. In addition, these preparations increase resistance to drought and root rot diseases due to stimulation of root system growth.
Wheat
Main article: Winter wheat
Main article: Spring wheat
History of wheat
Wheat is one of the oldest crops cultivated on the globe. Archaeological research shows that it was cultivated more than 6,500 years ago on the territory of modern Iraq, 6,000 B.C. – in Egypt, 3,000 B.C. – in China. Even in prehistoric times, wheat was cultivated in Africa and Europe.
On the territory of Russia, wheat was known in the Stone Age – about 3-4 millennia BC. It was cultivated in Turkmenistan, Transcaucasia and Ukraine. 3000 B.C. it was known in Georgia and Armenia and the traces of this culture were found on the territory of Khmelnitsky region of Ukraine dated IV millennium B.C. It was cultivated by the Scythians and later by the Slavs, who spread it north to Novgorod and Ladoga. In the 13th century it was cultivated in Khakassia and other areas of Siberia, such as the Krasnoyarsk Territory. The greatest diversity of wheat species is concentrated in Transcaucasia.
Economic importance
Wheat ranks first among other crops in world agriculture. The planted area is 230-240 million hectares, which is 32% of the total area of cereal crops. The gross harvest is 600 million tons, or 29% of total grain production. The average yield is 2.6 t/ha.
The USSR was in first place in the world by the area sown and the production of wheat grain. In 1976-1980 the area sown with wheat in the USSR averaged 60.7 million hectares. In the 1990s, the area sown in Russia was 25 million hectares, which was 11% of the world’s total area. In 2001-2005, the area of wheat planted was 24 million hectares, the gross yield was 44 million tons, or 57% of the total grain harvest, and the average yield was 1.83 t/ha.
There are large areas sown in the United States, China, India, Canada, Argentina, France and Australia. Wheat is cultivated on all continents, in the mountains up to 4000 m above sea level. In European countries and the United States, winter wheat is more common, while in Russia and Canada, because of the harsh climate, spring wheat is more common.
Wheat is the most important food crop: more than half of the world’s population consumes it for food. Wheat flour is used in baking and confectionary industries. Bread is distinguished by its high taste and nutritive qualities. Wheat grain is used to produce cereals, pasta, wheat starch, dextrin, alcohol, and other products.
Wheat bran and flour dust, the waste products of the milling industry, are used as concentrated animal feed. Straw and chaff are also used as fodder, but recently they have been increasingly used as an organic fertilizer.
The most important indicators of the quality of wheat are the protein and gluten content. Protein content is influenced by climate, soil conditions and fertilizers used. Protein content determines the nature of its use and can range from 9 to 26%, the digestibility of protein reaches 95%, lipid and ash content about 2% each. For baking, grain with a protein content of 14-15% is used, for pasta – 17-18%.
Nutritional value of 100 g of wheat bread is 245-255 kcal, 100 g of pasta – 355-358 kcal.
Wheat proteins are represented by albumin (soluble in water), globulin (soluble in saline solutions), prolamin (soluble in alcohols) and glutelin (soluble in weak alkalis and acids). Prolamins and glutellins form a hydrated gelatin, which is a clot that remains after the dough is washed of starch. This jelly is called gluten. Wheat protein contains up to 50% raw gluten.
To assess the baking properties of wheat flour, the quantity and quality of gluten are important and affect the volume yield of the bread, its looseness and the porosity of the crumb. According to physical properties, gluten is divided into:
- with good elasticity and medium elasticity;
- with satisfactory elasticity or strong extensibility;
- with unsatisfactory elasticity or poor extensibility.
The high volume yield of bread depends on the elasticity of the gluten and the gas retention capacity of the dough. Gluten elasticity should be no more than 30 cm and no less than 20 cm. Bread spreadability is the ratio of the height of the bread (dough) to its diameter. The spreadability of good quality bread should be greater than 0.5. The crumb should have a uniform thin-walled fine-grained porous structure.
Grains with a protein content of at least 11% are used for bread making, and at least 14% for pasta.
Strong (soft) and durum wheat
Strong and durum wheat are important for the milling, baking and export industries.
Strong wheat is only soft wheat, characterized by high protein, gluten and other nutrients. When evaluating the strength of wheat, baking properties are decisive. Three types of wheat are distinguished by their technological properties: strong, medium and weak.
Strong wheat is characterized by higher grain protein content of at least 14%, raw gluten content of at least 28%, gluten quality not lower than group I, volumetric yield of 100 g of flour 550 cm3, vitreousness of red wheat grain – at least 75%, white grain wheat – at least 60%, baking power of flour – at least 280 J.
Strong wheat is called an improver because it improves the baking qualities of weak wheat. The addition of strong wheat flour to weak wheat flour improves the qualities of the bread: taste, porosity, volume. Grain of strong wheat is valued on the international market.
Medium strength wheat (filler) has good baking qualities, bread from it is obtained with satisfactory qualities without the addition of stronger wheat, but it cannot improve weak wheat. Grain of medium wheat contains 11-13.9% protein, 25-27% gluten, gluten quality corresponds to group II, baking power of flour is 200-280 J.
Weak (weak) wheat has low baking power. The bread is of reduced volume, spreading on water. Grain of weak wheat has low protein content – less than 11%, raw gluten – less than 25%, quality of gluten corresponds to groups II-III, volume yield of bread from 100 g of flour less than 400 cm3, baking power of flour is less than 200 J. Strong wheat flour is added to standard bread from weak wheat flour.
Valuable wheat grains are those that have genetically increased flour strength, but not enough to be effective improving weak wheat grain quality. Valuable wheat grain must contain at least 25% gluten of group II quality or higher.
The grain of strong wheat is rated higher than that of common wheat. Grain of durum wheat is valued higher than grain of soft wheat.
Wheat varieties
In Russia, the most common varieties are strong in quality:
- winter wheat – Mironovskaya 808, Bezostaya 1, Odesskaya 51, Donskaya ostistaya;
- spring wheat – Albidum 43, Saratovskaya 29, Saratovskaya 39, Bezenchukskaya 98.
The most valuable varieties of winter wheat are Albidum 114, Ilyichevka; of spring wheat – Grekum 114, Minskaya, Moskovskaya 35.
Types
Wheat (Triticum) has 22 species, which belong to the family of cereals – Gramineae, or Poaceae. Soft wheat (Triticum vulgare L., or Triticum aestivum L.) and durum wheat (Triticum durum Desf.) occupy the largest areas in the world.
Soft, or common wheat, is more common, cultivated throughout Russia. There are winter, semi-winter, and spring forms of soft wheat. The spike is loose. The weight of 1000 seeds varies from 30 to 55 g. The front side of the ear exceeds the side, i.e., the width is greater than the thickness. Spikelet scales are wide, not completely covering the flowers. The keel on the spikelet scale is narrow, poorly developed, the grain has a well-defined tuft; it may be powdery, semi-stalky or vitreous in texture. There are spinous and spineless forms. The awns on the outer floral scales are shorter; the ears spread fan-shaped. The straw is hollow.
Durum wheat in Russia is represented mainly by the spring varieties. Winter forms are cultivated in small areas in the low-mountainous regions of Azerbaijan, eastern Georgia, Odessa region of Ukraine, and in Russia – in Dagestan, Siberia, Povolzhye, Kuban, Central Black Earth zone.
In the world, the main regions of durum wheat cultivation are the Mediterranean coast: Spain, France, Italy, Asia Minor, northern and southern Africa, USA, Argentina, Australia.
The ears of durum wheat are long, the spikelet scales strongly covering the flower; the keel is prominent, and the grain is completely immersed in the flower scales. For this reason, durum wheat resists shattering better, but it is also more difficult to thresh. The ear is thick and awned. The awns are parallel to and longer than the ear; the lateral side of the ear exceeds the front side, i.e., the thickness is greater than the width. Grain elongated, laterally compressed, with weakly expressed tuft or almost without it, glassy at break. Transverse section of the grain is angular, while that of soft grains is close to round. Weight of 1,000 seeds is 35 to 65 g. Straw of durum wheat is full or with a small aperture in the upper internode.
The gluten of soft wheat has more valuable properties, due to which bread made from soft wheat flour has better qualities. The gluten of durum wheat is tearable, so it is used to produce semolina and pasta.
Table. Morphological differences between soft and durum wheat
| Ear | Awned or awnless, loose. Face is wider than lateral | Awned, rarely awnless. Large, dense, cross-section square or compressed, lateral side wider than facial one |
| Awns | Equal to the ear or shorter, diverging sideways | Longer than the ear, pointing upwards parallel to the ear |
| Straw under the ear | More often hollow | More often filled with a core |
| Grain | Short with a tuft. On the break rounded, floury or semi-vitreous. Protein content 10-18%. | It is elongated. Spiracles weakly expressed or absent. On fracture angular vitreous. Protein content 16-24%. |
Most types of wheat, including soft and hard, turgidum, polonikum, dwarf, peach, and round grain, are holo-grain wheat characterized by an unbreakable ear shank. For this reason, after ripening, their ears do not break into spikelets, and the grains separate well from the spikelet and floral scales during threshing.
Emmer wheat, or filmy wheat, has a brittle spike shaft, so after maturity the ear breaks into spikelets, and at threshing the grain does not separate from the spikelets. Special crumbling are used to obtain clean grain of filmy species. The filmy species include wild and cultivated single-grain, double-grain, spelt, and maha. In some areas of the North Caucasus local varieties of emmer wheat are cultivated.
Varieties of soft and durum wheat
The division of species into varieties is based only on morphologically stable features of the ear and grain. This classification does not give an idea of the biological nature of the forms, does not connect them with ecology and geography. The classification is of practical importance because it serves for morphological systematics of varieties.
Characteristics of wheat varieties:
- awniness, i.e., the presence or absence of awns on the ear;
- pubescence of spikelet scales, which may also be glabrous;
- color of the ear, such as white, red, or black;
- coloration of awns: identical with the color of the ear or black in white and red ears;
- coloration of grains, most often white and red; grains with white coloration include pure white, yellowish and pale pink, with red – dark pink, red and reddish brown.
Each variety has a number of varieties that differ from each other, but not always, in morphological features, biological and production features. Within one variety there may be winter and spring varieties, early-ripening and late-ripening; they may differ in winter hardiness, drought tolerance, shattering, resistance to diseases and pests.
Most soft wheat varieties are lutescens, erythrospermum, ferrugineum, and miltrum. Durum wheat varieties are of the gordeiform and melanopus varieties.
Sources
V.V. Kolomeychenko. Horticulture/Textbook. – Moscow: Agrobiznesentr, 2007. – 600 с. ISBN 978-5-902792-11-6.
Horticulture/P.P. Vavilov, V.V. Gritsenko. Vavilov. ed. by P.P. Vavilov, V.S. Kuznetsov et al. – M.: Agropromizdat, 1986. – 512 p.: ill. – (Textbook and Tutorials for Higher Education Institutions).
Fundamentals of agricultural production technology. Farming and plant growing. Ed. by V.S. Niklyaev. – Moscow: “Bylina”. 2000. – 555 с.