Economic importance and geography of winter and spring wheat cultivation

Economic Significance and Geography of Wheat Cultivation

Wheat is a key cereal crop on the planet, providing food for about 70% of the Earth's population. The grain is widely used for the production of flour, bread, semolina, pasta, and confectionery. In livestock farming, a byproduct of processing — bran — is in demand, serving as the basis for the production of compound feed.

• Share in global grain production — about 30%
• Global sowing area — nearly 210 million hectares
• Protein content in grain — 10–20%
• Starch content in grain — 63–74%
• Average yield in Belarus — 30–32 centners/hectare
• Annual gross harvest in Belarus — 1.0–1.2 million tons

In addition to protein and starch, wheat grain contains approximately 2% each of fat, fiber, and ash. Crops of this plant occupy almost half of all global arable land dedicated to cereals. China and India remain leaders in cultivation, followed by the USA and Russia. The geography of cultivation covers almost all continents — from Southern Africa to the Arctic, and in the mountains, crops are grown up to 4000 meters above sea level.

In the CIS region, the distribution of winter and spring forms is strictly tied to the climate. In the chernozem regions of Ukraine, the North Caucasus, and Central Russia, winter forms occupy about 3/4 of the area. Conversely, in the steppe regions of the Volga region, Siberia, and Kazakhstan, spring cultivars account for up to 90% of all crops.

In the Republic of Belarus, sowing areas for winter and spring soft wheat are expanding to achieve self-sufficiency in food grain. Previously, 60–100 thousand hectares were allocated for the crop in the agricultural complex. In 2006–2007, sowings increased to 350–420 thousand hectares.

The dynamics of global wheat grain production by country are presented in the table:

Country	1985, thousand tons	1995, thousand tons	2005, thousand tons
China	85 807	102 212	96 160
India	44 069	65 767	72 000
USA	65 975	59 404	57 106
Russia	30 119	-	45 500
France	28 784	30 880	36 922
Canada	24 252	24 989	25 547
Australia	15 999	16 504	24 067
Germany	13 802	17 763	23 578
Pakistan	11 703	17 002	21 591
Turkey	17 032	18 015	21 000

Origin and Evolution of Cultivated Species

Wheat is considered one of the oldest cultivated plants on Earth. Its original centers of cultivation emerged in Western Asia back in prehistoric times. Archaeological data show that the crop was known in Mesopotamia over 6500 years BC, and by the 6th–5th millennia BC, it was already being sown in Egypt, Syria, and Asia Minor.

By the 3rd millennium BC, wheat began to be grown in Armenia, Turkmenistan, India, China, and also on the territory of Ukraine (within the Tripolye culture). Slavs extended crops far to the north, up to Novgorod and Ladoga, as early as the time of Kievan Rus. On the American and Australian continents, the crop appeared much later: it was brought to Latin America in 1528, cultivation began in the USA in 1602, in Australia in 1788, and in Canada in 1812.

The oldest and most unpretentious type of wheat was emmer, represented mainly by spring forms. Its main drawback is the difficulty of milling: the grain is threshed from the brittle ear only together with the attached floral and glume scales. Due to this anatomical feature, it is technologically difficult to process such grain into flour.

Today, emmer has been almost completely replaced by soft and durum wheat. In agricultural production, it is rarely found — mainly on the Mediterranean coast, in Syria, Ethiopia, and it is also used by breeders for hybridization. Under the influence of climate and continuous selection, cultivated species have changed significantly. Wild emmer and einkorn have lost their characteristic ear brittleness during ripening and have increased stem height and grain size.

As early as 6–7 thousand years BC, cultivars were created in many countries that differed little from modern ones. The systematic genus Triticum belongs to the Poaceae (grass) family and includes 22 species, which are well distinguishable by morphological characteristics. Based on chromosome number, the variety of cultivated species is divided into 4 genetic groups.

• diploid (14 chromosomes);
• tetraploid (28 chromosomes);
• hexaploid (42 chromosomes);
• octoploid (56 chromosomes).

Cultivated wheat species, according to cytogenetic studies, combine three genomes (A, B, D), which apparently originate from three wild grasses growing in Asia Minor, Southern Europe, and North Africa.

Only 2 species have the greatest production significance in global agriculture:

hexaploid soft (Triticum aestivum L., or Triticum vulgare Host.)	90% of sowings
tetraploid durum (Triticum durum Desf.)	the remaining part

Fig. 14. Wheat species: 1 — common bearded; 2 — common beardless; 3 — durum; 4 — einkorn; 5 — emmer; 6 — Timopheevi wheat; 7 — polonicum; 8 — dwarf; 9 — turgidum of the first group 139

Among the other 20 species, the following have gained some distribution:

• turgidum wheat, or English wheat (Tr. turgidum L.), which has branched-ear forms, grains are short, oval, with truncated tips, which is why they appear swollen and humpbacked and can be red-violet or white;
• Polish wheat (Tr. polonicum L.), distinguished by its appearance. Its ear is large — 15—18 cm long and 2 cm or more wide; glumes are long, thin, papery, and the grains often reach 13 mm in length and are very hard.

Cultivars of this species, like those of durum wheat, are only spring-grown.

All wheat species are annual plants. The root system of wheat is fibrous, located mainly within the depth of the ploughing layer. The aerial part (stems, leaves, ears) reaches 0.5—2 m in height. The stem contains 5—7 nodes.

All wheat species are practically divided into two groups: naked and hulled (glumaceous).

Naked species have a non-brittle rachis; their ear does not disintegrate into individual spikelets, and the grain is easily separated from the husks. Hulled wheats have a brittle rachis; upon maturity, the ear disintegrates into spikelets (with geniculate rachis segments), and the grain remains inside the spikelets and husks during threshing.

Naked wheat species include the following:

• common wheat (Tr. vulgare Host.),
• durum wheat (Tr. durum Desf.),
• Polish wheat (Tr. polonicum L.),
• turgidum wheat (Tr. turgidum L.),
• Vavilov wheat (Tr. vavilovii Jakubz.),
• carthlicum wheat (Tr. carthlicum Nevski),
• dwarf wheat (Tr. compactum Host.),
• sphaerococcum wheat (Tr. sphaerococcum Perc.),
• turanicum wheat (Tr. turanicum Jakubz.),
• amplissifolium wheat (Tr. amplissifolium Zhuk.),
• fungicidum wheat (Tr. fungicidum Zhuk.).

The remaining 11 species are considered hulled (glumaceous) wheats:

• wild einkorn (Tr. aegilopoides Link.),
• cultivated einkorn (Tr. monococcum L.),
• wild emmer (Tr. dicoccoides Aar.),
• emmer (Tr. dicoccum Schubl.),
• spelt wheat (Tr. spelta L.),
• Abyssinian wheat (Tr. aethiopicum Jakubz.),
• araraticum wheat (Tr. araraticum Zhuk.),
• Urartu wheat (Tr. urartu Thum.),
• Zanduri (Tr. timopheevii Zhuk.),
• Colchian emmer (Tr. paleo-colchicum Men.),
• Macha wheat (Tr. macha Dek. et Men.).

Winter, spring, and facultative (dual-purpose) wheats are distinguished.

Winter wheats require a fairly long period of exposure to low temperatures at an early stage of development (i.e., vernalization) for normal fruiting. Winter wheat is sown in autumn and harvested the following summer. It is the most widespread wheat worldwide. Beginning its development earlier than spring wheat, which is sown in spring, winter wheat matures faster and provides a higher yield.

Facultative forms require only brief cooling during the same initial stage of ontogenesis for normal fruit set, while spring wheats develop and fruit normally if the entire period of initial development occurs at temperatures above 0 °C.

The names themselves — soft (common) and durum (hard) wheats — aptly characterize the differences between them.

Durum wheat has the following morphological and biological traits: the ear is coarse, dense, and bearded; the two-row side of the ear is wider than or equal to the face side. The awns are long, extended parallel upwards. The glumes are rigid and hard. The grain is elongated, vitreous without a tuft, tightly enclosed in flowering and glume scales, and does not shatter upon maturity. The stems of durum wheat species are taller than those of common wheat; the straw under the ear is completely filled with parenchyma or has a narrow lumen. The leaves are smooth and leathery. The plants are resistant to lodging and shattering, and are less affected by pests and diseases (rust, powdery mildew, loose and covered smut), although they have no immunity to these pathogens. In wet years, durum wheats can be affected by ergot.

Among durum wheat species, mainly spring forms are used in production, which cover about 4 million hectares in Russia. Facultative forms are rarer. In the 1950s, in the USSR, at the Selection and Genetics Institute (Odessa), the winter durum wheat 'Michurinka' was created for the first time, possessing high yield and baking qualities; subsequently, other winter durum wheat cultivars were developed. Durum wheat is represented by forms with both a very short vernalization stage (5 days) and a very long light stage — up to 40—45 days.

Durum wheat cultivars are also cultivated in North and South Africa, Australia, Spain, France, Italy, Turkey, and in the steppe regions of the USA, Canada, and Argentina.

Biological features of soft and durum wheat

Soft wheat possesses unique ecological plasticity, which allows it to be cultivated in a wide variety of zones — from the Non-Chernozem region and forest-steppe to the solonetzic soil of semi-deserts. When working with this crop, it is important for an agronomist to consider the features of its structure: the culm is hollow, the leaves are pubescent, and the glumes do not tightly cover the grain. Because of this, soft wheat is easily threshed, but sheds quickly if left standing in the field too long. The awns on the spike are either completely absent or do not exceed its length.

Winter forms of soft wheat are sown in regions with a moderately cool climate, stable snow cover, and relatively mild winters. In zones with severe winters and a continental climate, spring wheat is grown. The development of winter crops is strictly tied to the temperature regime and moisture availability.

• Temperature for onset of growth — 3–4 °С
• Moisture requirement for seed swelling — 45–50% of dry grain mass
• Time to reach tillering at 12–15 °С — 15 days
• Growing season (including wintering) — 275–350 days
• Sum of positive temperatures during the growing season — 1850–2200 °С
• Temperature for flowering and fertilization — 12–30 °С

Winter wheat effectively uses spring and autumn moisture, but the peak of water consumption occurs during the period from shooting to flowering. Compared to winter rye, it is more drought-resistant and heat-tolerant, yet it places higher demands on soil fertility and the quality of predecessors. Due to weak tillering, wheat shades the soil less and is more strongly suppressed by weeds, so it is placed in fields clean of weed vegetation. Spring wheat develops slowly during the first 15 days of the growing season — this period is critical for the crop, when the sowings are in acute need of care, mineral nutrition, oxygen, and moisture.

Durum wheat is divided into two key subspecies. The Mediterranean subspecies is characterized by late maturity, long awns, a large spike, and large grain. The Abyssinian subspecies consists of early-maturing, short-stature plants with weak tillering.

Technological properties of grain and classification

Wheat varieties are classified by external signs: the presence of awns, pubescence of glumes, and the color of the spike, awns, and grain. Most soft wheat cultivars belong to the erythrospermum, ferrugineum, lutescens, albidum, milturum, and caesium varieties. Among durum wheat, the hordeiforme and melanopus varieties predominate. In commercial classification, grain is divided into types based on botanical and biological traits, as well as into subtypes based on color and general vitreousness, which directly determines its future industrial use.

Wheat grain is distinguished by a high endosperm content (80–84%), which guarantees a high yield of high-grade flour during processing. Wheat flour is rich in vitamins B1, B2, PP, as well as calcium, phosphorus, and iron. In terms of nutritional properties, wheat bread exceeds rye bread in caloric value and content of easily digestible protein.

Indicator (per 1 kg of bread or in dry matter)	Wheat bread	Rye bread
Energy value, kcal/kg	2000–2500	about 1800
Protein content in dry matter, %	16–17	14–15
Protein digestibility, %	95	—
Carbohydrate content, %	77–78	—
Lipid content, %	1.2–1.5	—

Physical properties of flour determine its purpose. Soft wheat flour is white, finely milled; its gluten consists 80% of gliadin and glutenin, which makes the dough elastic and stretchable, allowing it to rise well. However, products made from such flour lose their shape and fall apart in hot water. Durum wheat flour has a yellowish tint and a pronounced granular structure, and the dough made from it is stiffer and requires less flour during kneading. Due to its short and elastic gluten, durum wheat is indispensable for the production of pasta that retains its shape during cooking, as well as for semolina and confectionery products.

The final baking qualities of the finished product directly depend on the volume and properties of the gluten. When evaluating breeding cultivars, the baking strength of the flour plays a key role. This indicator refers to the specific work of deformation of one gram of dough, expressed in ergs.

Varietal composition of wheat and yield potential

Flour strength determines the baking qualities of wheat. Cultivars with high technological grain properties are classified as strong. The quality of raw materials in this group is evaluated by protein content, grain vitreousness, and the physical properties of gluten — elasticity and extensibility.

• Protein content in strong wheat — no less than 16%
• Grain vitreousness — no less than 70%
• Flour strength of very strong cultivars — more than 400 ergs
• Flour strength of strong cultivars — 301–400 ergs
• Flour strength of medium cultivars — 221–300 ergs

Strong spring cultivars include wheat-couch grass hybrids. The strong winter wheat group includes the cultivars Novoukrainka 83, Bezostaya 1, Bezostaya 4, Mironovskaya 808, and Saratovskaya 29. The basis of wheat production in the Russian Federation is soft wheat, which occupies 90% of the sown area and is used for baking bread, confectionery, and partially for pasta flour. Hard wheat accounts for 10% of the area; its grain is used for the production of pasta flour and serves as an improver for weak batches of soft wheat.

In the geographical structure of the winter crop acreage, almost half of the area of the CIS countries is in Ukraine. In recent years, winter wheat has also been actively cultivated in the non-chernozem zone of Russia and Belarus. The average yield of the crop in the Russian Federation in the period 2003–2005 was 30–40 centners/ha. In the Republic of Belarus, winter wheat occupies 70% of the sown area of the agro-industrial complex.

Winter wheat breeding is focused on creating cultivars with a multi-flowered productive ear, high baking qualities, and resistance to lodging and pathogens. When creating new cultivars and triticale, breeders use the genetic potential of proven cultivars such as Leningradka, Mironovskaya 808, and the short-stemmed, non-lodging cultivar Dalchik. In total, 26 cultivars of winter wheat are cultivated in production, more than half of which are cultivars of domestic breeding: Suzor’e, Prem’era, Uzlet, Kapylanka, Garmonija, Legenda, Karavay, Bylina, Sjuita, Shchara, Zavet, Spektr, Sanata, Fantazija, and Hrodzenskaya 7. Farms also use foreign cultivars: the German Dekan, Kubus, Lars, Sukces and the Polish Sakva, Tanacja.

Among the cultivated cultivars, there are various maturity groups:

• early-maturing — Shchara;
• medium-maturing — Kapylanka, Sanata, Lars;
• medium-late-maturing — Zavet, Prem’era, Uzlet, Spektr;
• late-maturing — Garmonija, Legenda, Karavay, Bylina.

The cultivars Bylina, Legenda, and Kapylanka are included in the list of the most valuable in terms of grain quality for baking. Productivity indicators of winter and spring cultivars according to test data are given in the tables below.

Test results for winter wheat cultivars (data for 2006–2007)

Cultivar	Average yield, centners/ha	Maximum yield, centners/ha	Agronomic characteristics of cultivars
Dekan	80.8	108.4	Good winter hardiness, short stem, low lodging, medium resistance to powdery mildew, septoria, snow mold, and root rots.
Kubus	80.1	107.9
Tonacja	78.3	107.3
Lars	70.3	97.8
Fantazija	68.8	93.6

In trials at the agricultural experimental station, an average spring wheat yield of 89.5 centners/ha was obtained. Data on the yield of promising cultivars are shown in the table:

Test results for promising spring wheat cultivars

Spring wheat cultivar	Yield in experiments, centners/ha	Resistance to pathogens
Koksa	68.1	Medium resistance to powdery mildew, snow mold, and root rots.
Sofya	62
Toma	61

System of pre-sowing seed and soil treatment

Rust, smut, and root rots can significantly reduce wheat yield. Protective measures are based on the introduction of resistant cultivars and mandatory chemical treatment of seed material. Seed treatment is an economically efficient technique with low costs per hectare.

For reliable fixation of preparations on seeds, an encrustation method is used with the use of film-forming agents and adhesives. A 2% solution of NaCMC glue is used as a film-forming agent. This prevents the preparation from shedding during transport and sowing.

The selection of plant protection products for seeds is carried out in a strict sequence based on preliminary diagnostics:

1. Conduct a phyto-examination of seed material to accurately determine the species composition of pathogens and the degree of batch infestation.
2. Form a list of effective seed treatments whose spectrum of action covers the detected complex of pathogens.
3. Choose the most economically advantageous product from the list of permitted preparations.
4. Carry out seed treatment with the addition of adhesives or film-forming agents.

The system of basic and tillage pre-sowing soil treatment for winter wheat is determined by the type of predecessor, field weediness, and specific soil and climatic conditions. The quality of seedbed preparation is of decisive importance for overwintering and the development of seedlings. Proper tillage ensures uniform emergence and an optimal start for plants in the autumn period.

Predecessors, tillage, and nutrient system

The choice of predecessors and the quality of soil preparation directly determine the overwintering potential of winter wheat. The crop is demanding regarding soil conditions: it produces the most stable yields on fertile, sufficiently moist, and weed-free dark chestnut soils with a neutral reaction (pH 6–7.5). In the Non-Chernozem region, wheat is successfully cultivated on weakly podzolic, grey forest, and medium-loam soils.

In crop rotations, the structure of predecessors depends on the cultivation zone. In regions with insufficient or unstable humidity, bare (black) fallows remain the best choice. Where moisture is sufficient, winter wheat is sown after catch-crop fallows — following a vetch-oat mixture, perennial grasses, lupine for green forage and silage, peas, or early potatoes.

The tillage technology for winter wheat depends on the preceding crop and the level of weed infestation in the field:

1. After perennial grasses and annual crops: tillage begins with mandatory disking in two directions using disk harrows for high-quality sod cutting and moisture conservation. Then, stubble breaking, deep ploughing with a pre-plough, and harrowing are performed. As weeds appear, the field is cultivated with simultaneous harrowing.
2. After row crops (on weed-free fields): cultivation to a depth of 10–12 cm with harrowing is performed. In a dry summer, the field is additionally rolled with harrowing for better soil settling, while combined tillage implements are used in conditions of sufficient moisture.
3. On slightly weed-infested soils after a predecessor: complex processing is performed — cultivation to a depth of 5 cm, harrowing, and sowing. In spring, the crops are harrowed to conserve soil moisture.

Winter wheat is responsive to fertilizer, especially on poor podzolized soils. Yield growth here depends on enriching the soil with organic matter.

Type of fertilizer	Application rate, t/ha
Manure	2,5–3,0
Manure-phosphate compost	1,5–2,0

Among mineral fertilizers on poor soils, ammonium nitrate (20–40 kg/ha), superphosphate (20–30 kg/ha), and potash salt (15–20 kg/ha) are applied. Granulated superphosphate is also applied in rows during sowing along with the seed, which is most effective on sod-podzolic soils.

Nitrogen top dressing is distributed according to plant development phases:

• Spring (start of the growing season): root top dressing is carried out at a depth of 4–6 cm using grain seed drills; the application rate is 40–60 kg/ha.
• Tillering phase: root top dressing to stimulate shoot formation.
• Heading phase: foliar top dressing with ammonium nitrate or urea to increase protein and gluten content in the grain.

The necessity of applying micronutrient fertilizers is assessed based on the results of soil or visual diagnostics. In case of copper deficiency, plants acquire a light green color. Manganese shortage manifests as necrosis on leaves, weak root development, and increased susceptibility to disease. Micronutrient application is combined with seed treatment or spraying crops with fungicides, herbicides, and growth regulators.

• Copper: applied on sod-podzolic and grey forest soils.
• Manganese and zinc: applied on chestnut, light-loam, and drained peaty soils.

Biological characteristics and temperature regime

The growing season of winter wheat lasts from 240 to 320 days. Plants go through several critical development phases, the requirements of which for temperature and humidity differ significantly.

• Start of seed germination — 1–2 °C
• Optimal temperature for uniform emergence — 12–15 °C
• Seedling emergence (at 12–15 °C) — 7–9 days
• Optimal tillering temperature — 8–10 °C
• Critical frost without snow — -16...-18 °C

The tillering capacity of winter wheat ranges from 1 to 15 or more stems. Tillering occurs during the autumn and winter periods. The intensity of shoot formation increases with good soil moisture availability and the application of nitrogen fertilizer. By the end of the autumn growing season, 4–5 shoots are formed on average from the tillering node.

The success of overwintering depends on the degree of root system development and the presence of snow cover. By the beginning of winter, the wheat root system is capable of reaching a depth of up to 1.5 m. In snowless winters, temperatures below −16...−18 °С are fatal for crops. At the same time, frost resistance strongly depends on the cultivar: for example, the winter wheat cultivar Mironovskaya 808 can withstand winter frosts down to −30 °С without damage.

Common wheat varies significantly in height: from the short-stemmed domestic cultivar Dalchik (about 45 cm) to tall forms reaching 200 cm. Its long stem is hollow and consists of 5–6 internodes, which often causes such plants to lodge.

The growing season of spring cultivars depends heavily on the response to day length (the light stage lasts from 5 to 25 days or more) and the geography of cultivation. Early-maturing cultivars ripen in 70 days, while late-maturing ones require up to 120–130 days.

Spring wheat is demanding in terms of nutrition and soil quality. On relatively poor sod-podzolic lands, liming is mandatory, and organic-mineral mixtures are applied. The best yields are obtained on neutral and slightly acidic soils. Insufficient soil moisture, high acidity, and seed contamination lead to weak and uneven emergence.

The best predecessors for spring wheat in crop rotation are clean fallows (especially in the steppe zone) or fields after occupied fallows where perennial legumes predominated.

To accumulate and retain moisture in the fields, snow retention is carried out. An important technique is also the retention of meltwater using deep ridged autumn ploughing.

The fertilization system for spring wheat is structured according to the following scheme:

1. Application of organic fertilizers (manure, peat-manure compost) before primary tillage.
2. Application of phosphorus and potassium mineral fertilizers in the autumn before primary tillage.
3. Application of nitrogen fertilizers in the spring before cultivation (in arid zones, the full fertilizer rate is incorporated during ploughing or applied during sowing along with the seed).
4. Top dressing with nitrogen fertilizers during the tillering stage.

Sowing, Plant Protection, and Harvesting Technology

Spring wheat belongs to crops with the earliest sowing dates. Delaying sowing leads to a sharp drop in yield. Sowing is carried out using narrow-row or cross-sowing methods — this makes the stand more resistant to lodging and reduces thinness of the crop. On heavy and medium loams, the sowing depth is 3–4 cm. When sowing on peat-bog soils, rolling before and after the seed drill is mandatory.

Crop care includes harrowing, rolling, and protection from weeds, pests, and diseases. Treatment schemes:

• Against annual grass and broad-leaved weeds: spraying with herbicides "Kugar" or "Marafon" 2 days after sowing (before emergence) or at the crop's tillering stage.
• Against sow thistle, chamomile, and knotweed: spring spraying with the product "Lontrel 300" at the wheat tillering stage.
• Against cereal thrips on winter wheat: treatment with insecticides "Aktellik" or "Karate" during the booting stage.
• Against powdery mildew, rust, and septoria on winter wheat: application of fungicides "Rex", "Sportak", or "Tilt".

Harvesting of winter wheat should take place within a tight timeframe — 6–7 days to avoid grain losses. In the wax ripeness stage, a two-phase (separate) harvesting method is used; in the full ripeness stage, direct combining. The choice of method depends on the field size, density, and height of the stand. Spring cultivars are harvested using a single-phase or two-phase method at a grain moisture content of at least 15–20%.

• Spring wheat growing season — 75–115 days
• Application rate for narrow-row sowing — 7–7.5 million viable seeds/ha
• Application rate for row sowing — 6–6.5 million seeds/ha (2–2.5 centners)
• Sowing depth on loams — 3–4 cm
• Winter wheat harvesting period — 6–7 days
• Grain moisture content during harvesting — at least 15–20%