Technological directions of flax cultivation and its economic significance

Technological trends and economic importance of flax

Spinning crops are grown to obtain natural plant fiber, with cotton, jute, flax, and hemp holding leading positions in global production. Unlike cotton, which forms fiber on seeds, flax accumulates it in the stem. Almost all spinning crops provide seeds with a high content of technical and edible oil, as well as oilcake for livestock. Flax cultivation practice employs three production directions, each requiring a specific approach to harvesting.

Growing flax solely for fiber is carried out by harvesting during the flowering phase (green flax). Thin fiber for lace production is extracted from immature stems, with the fiber content in fiber flax stems reaching up to 33%, while oil flax stems contain almost half as much. When cultivating oil flax, the goal is the seeds, which yield up to 47% of valuable oil by weight. The short stems of oil flax are processed into tow, twine, rope, and coarse industrial fabrics.

The most common method is the combined approach — growing fiber flax for both fiber and seeds simultaneously. Harvesting in this case is carried out in the early yellow ripeness phase. This allows obtaining from 16% to 30% of high-quality fiber and collecting ripe seeds for oil extraction. The resulting fabrics are resistant to decay and wear, becoming stronger with increased humidity during use.

Flax production is practically zero-waste. Short fiber (tow and oakum) serves as wiping material and insulation, while flax shive, containing up to 64% cellulose, is used in the manufacture of construction boards, paper, and cardboard. After oil extraction, oilcake remains — a most valuable concentrated feed for young animals and livestock. Its nutritional value and mineral composition make this byproduct an important source of income for a flax-growing enterprise.

Nutritional value index of flax oilcake	Content (per 1 kg of feed) / share
Feed units	1.15
Protein substances	up to 36%
Digestible nitrogen-free substances	up to 32%
Oil	up to 12%
Calcium	4.3 g
Phosphorus	8.5 g
Carotene	2 mg

Yield potential and structure of sown areas

Global areas under oil flax amount to nearly 1 million hectares, with the main crops concentrated in the USA, Canada, Argentina, and India. CIS countries account for about 10% of this area, but at the same time, up to 60% of global fiber flax crops (1.5 million hectares) are concentrated here. Other major fiber producers include China, Poland, and the Netherlands. The average global fiber yield is 0.4 t/ha with a potential of up to 1.6 t/ha.

Belarus produces one-third of flax fiber in the CIS, providing 9% of the global and 16% of the European volume. Due to a decrease in economic motivation, the sown areas in the republic decreased and amounted to 80.7 thousand hectares (1.6% in the crop structure) in 2001. However, the high need for raw materials in the absence of own cotton bases returned strategic importance to flax. Today, the demand for flax products on the global market is growing steadily, despite the abundance of synthetics.

Domestic breeders have created new flax cultivars that surpass their predecessors in a complex of economically useful traits. According to data from experimental stations, when plants are provided with all nutrients, the potential of cultivars reaches 1.7–2.5 t/ha for fiber and 7–10 centners/ha for oil seeds. In the most favorable year of 2008, the average fiber yield in seed production plots was 17.2 centners/ha. Now, the industry faces the task of ensuring a gross fiber production volume of 60 thousand tons per year.

• Potential of domestic cultivars for fiber — 1.7–2.5 t/ha
• Potential for oil seeds — 7–10 centners/ha
• Target fiber yield — at least 10 centners/ha
• Target seed yield — 6–7 centners/ha
• Planned gross fiber production — 60 thousand tons per year

Cultivar potential and classification by maturity groups

Cultivar composition is a key factor in the profitability of flax growing. Modern breeding is aimed at creating fiber flax cultivars with high resistance to lodging, excellent fiber quality, and high adaptability to adverse weather conditions. The correct choice of seed allows for a significant increase in productivity without additional costs.

• Number of fiber flax cultivars in the register — 30
• Number of oilseed flax cultivars in the register — 2
• Number of cultivars bred by the specialized institute — 12

As of 2010, 30 fiber flax cultivars have been approved for the state register, including Aley, Borets, Blakit, Velich, Zador, Zakaz, Yitka, Iva, Levit, Ritm, Tabor, Fort, Yarok, as well as 2 oilseed flax cultivars — Lirina and Rucheek. Of these, 12 cultivars were developed by breeders at the specialized research institute. In the structure of commercial crops for 2007, the main share was distributed among five key cultivars.

Cultivar	Share in the cropping structure, %
Mogilevsky	30.7
K65	14.5
Dashkovsky	14.4
Lira	10.6
E68	9.6

New breeding achievements show high productivity in fiber yield. According to the results of tests at experimental stations, promising cultivars significantly exceed standard performance. Yield data for the new cultivars are presented in the table.

Cultivar	Fiber yield at experimental stations, centners/ha (%)
Zakaz	66.9
Ritm	62.0
Mogilevsky	61.2
Belita	61.1
Fort	59.8
Lida	58.3
Bonet	58.2
Aley	57.3
Iva	56.1
Borets	54.5
Vita (standard)	53.3

To optimize the harvesting campaign and reduce the load on machinery, crops must be formed from cultivars of different maturity groups. Categorization by maturation rates allows for the scheduling of desiccation and pulling. Based on the duration of the growing season, three groups are distinguished:

• Early-maturing cultivars: Vesna, Leto, Ritm, Praleska;
• Mid-maturing cultivars: Aley, Blakit, Zgoda, Niva, Rodnik, Fort;
• Late-maturing cultivars: Belinka, Vasilek, Zakaz, Laura, Mogilevsky, Pramen.

Biological characteristics and cultivation requirements

Fiber flax crops are demanding of climate and responsive to the soil texture. The crop shows the best results on loamy soils in regions with a moderately warm and humid climate. Flax has strict requirements for the acidity of the soil solution.

The crop has a rich history of cultivation, dating back to the Bronze and Iron Ages. Wild flax served as a source of oil and fiber in Egypt, India, China, Mesopotamia, and Transcaucasia 4–5 thousand years BC. In Slavic lands, flax spread in the X–XIII centuries, and Novgorod and Pskov became recognized centers of the flax trade. A state decree in 1711 stimulated the development of flax production in all provinces, which made the country the world's leading exporter of fiber by the beginning of the XX century.

In botanical classification, the genus Linum of the family Linaceae unites more than 200 species. Only common flax (Linum usitatissimum L.) is of practical interest for agriculture. Narrow-leaf flax (L. angustifolium L.), wild-growing thickets of which are found in the mountain subtropics of Asia and in northern Spain, is considered the likely ancestor of cultivated forms.

Each subspecies has its own biological characteristics and purpose. The Mediterranean subspecies (subsp. mediterranium) consists of short plants up to 50 cm with large seeds weighing 10–13 g. The intermediate subspecies (subsp. transitorium), with a height of 50–60 cm, has a thousand-seed weight of 5–6 g and is cultivated for oil in the south of Ukraine, in Crimea, Transcaucasia, and Kazakhstan. The Eurasian subspecies (subsp. eurasiticum) is the most common in production and is distinguished by small seeds weighing 3–5 g.

Depending on the agricultural focus, the Eurasian subspecies is divided into two main production groups. Fiber flax (elongata) forms a stem 60–175 cm high with minimal branching and a small number of bolls (2–3 in dense sowing, up to 6–10 in the average), ensuring a high yield of long fiber in moderately warm and humid climates. Intermediate flax (intermedia), 55–65 cm high, has 15–25 bolls, provides 16–18% of total fiber (including 13–14% scutched fiber), and is grown for seeds in the forest-steppe part of Ukraine, Kursk, Voronezh, Kuybyshev, Saratov regions, Bashkiria, Tataria, the North Caucasus, and partially in Siberia.

Stem anatomy and characteristics of flax varieties

To obtain high-quality raw materials, it is important for an agronomist to distinguish the morphological features of flax types. Flax-curly (rogachik, brevimulticaulia) has a short stem 30–45 cm high, which branches at the base and along its entire length. It produces from 35 to 50 bolls. This variety is cultivated to obtain seeds with an oil content of 32–47%, whereas its fiber is short and of low quality. The crop is adapted to the conditions of Central Asia and Transcaucasia, preferring a dry, warm summer with an abundance of sunny days.

Prostrate flax (prostrata) forms multi-stemmed bushes that are spread on the ground before flowering and rise during flowering. Its long shoots are suitable for obtaining fiber, however, cultivation volumes in Azerbaijan, Armenia, and Dagestan are extremely limited.

In industrial fiber production, the anatomical structure of the fiber flax stem is of key importance. In cross-section, it consists of an epidermis with a waxy coating, cortex, cambium, xylem, and pith with a central cavity. Bast fibers are located in the cortex in bundles or as a continuous cylinder consisting of cells 40–60 mm (up to 120 mm) in length and 20–30 mm in diameter. The quality of the raw material is uneven: at the base of the stem, the fiber is coarse and partially lignified, while the most valuable part (26–31% of the stem mass) is concentrated in the middle zone — from the cotyledons to the first branch of the inflorescence.

• Oil content of oilseed flax seeds — 32–47%
• Fiber yield in the middle part of the stem — 26–31%
• Length of high-quality fiber flax stem — more than 70 cm
• Diameter of high-quality fiber flax stem — 1.0–1.5 mm
• Number of bolls in the fiber flax inflorescence — 2–10 pcs.
• Duration of field flowering — 6–10 days

In dense crops, fiber flax grows as a single tall stem with a short umbellate inflorescence of 2–10 seed bolls. Leaves up to 40 mm long and 2–4 mm wide are arranged spirally and fall off upon ripening. The regular-shaped flowers have five stamens and five anthers.

Most often the petals are blue (such plants are the most productive), more rarely — pink or white. Flax is self-pollinating, although cross-pollination by bees is also possible. Field flowering takes 6–10 days: on clear days, buds open at 5–6 a.m., and by 10 a.m. the petals fall off. The formed fruit is a spherical five-celled boll measuring 8.3 × 5.7–6.8 mm.

Agroclimatic requirements and crop nutrition regime

To obtain a high yield of fiber flax, moderate spring-summer temperatures with alternating rain and clear weather are necessary. Seeds germinate at 5 °C, and seedlings are capable of withstanding short-term frosts down to −3...−5 °C. At the seedling stage, an air temperature of 9–12 °C is optimal, and 16–18 °C is required for subsequent growth and development.

Growing season of fiber flax lasts 75–85 days, increasing to 100 days or more in cold, rainy weather. The light development stage takes 20–28 days at an optimal temperature of 12–15 °C, while the vernalization stage passes in 5–10 days. The sum of active temperatures during the growing season is 1600–1800 °C (specifically for fiber flax — 1100–1500 °C).

The poorly developed root system of fiber flax limits its ability to absorb nutrients from the soil. Furthermore, nutrient uptake occurs over a compressed period. During the period from the "fir-tree" stage to the end of flowering, plants absorb two-thirds of all nutrients required for the entire growing season.

Development stage	Stage duration, days	Nitrogen uptake, %	Phosphorus uptake, %	Potassium uptake, %
"Fir-tree"	22	36	15	12
Budding	28	48	65	59
Flowering and ripening	16	16	20	29

The crop is demanding regarding soil conditions. For normal development, flax requires fertile areas with a humus content of about 2%, free from weeds, sufficiently moist, and well-aerated. In the conditions of Belarus, cultivated sod-podzolic medium and light silty loams with a slightly acidic reaction (pH 5.6–6.0) and a low degree of podzolization are considered best for cultivation.

Crop rotation rules, soil preparation, and balanced nutrition

Fiber flax is demanding regarding predecessors. It is best to place it after row crops (potatoes, sugar beet, corn), grain legumes, winter cereals, and perennial grasses. However, avoid sowing directly on a clover sod on cultivated and fertilized soils. Excess nitrogen nutrition in this case leads to plant lodging and the production of coarse, branching fiber. At the same time, after perennial grasses, flax yields excellent harvests and is less frequently affected by fusarium.

Compliance with the phytosanitary interval is a rule for flax growers. It is permitted to return the crop to the same field no sooner than after 5–6 years, otherwise soil exhaustion is inevitable. Dangerous pathogens accumulate in the soil and crop residues, causing fusarium wilt, anthracnose, septoria, polysporosis, sclerotinia, gray rot, rust, and bacterial diseases. Flax itself depletes the land only slightly: wheat, rye, and buckwheat grow excellently after it, and with the application of fertilizers — potatoes and beets.

Field preparation begins long before sowing. On fields with a shallow arable horizon, its depth should be increased gradually 2–3 years before sowing flax, necessarily combining this process with the application of organic and mineral fertilizers. Spring tillage of winter-ploughed fields should create a leveled, well-loosened, and weed-free seedbed, while preserving soil moisture in the seed layer. Only readily available forms of mineral fertilizers are applied for flax.

Soil type by nitrogen content	Recommended element ratio (N:P:K)
Nitrogen-poor	1 : 2 : 3
Nitrogen-rich	1 : 3 : 4

The weak root system of flax requires intensive nutrition in a short timeframe. The plant absorbs the bulk of its nutrients at the very beginning of the growing season. Nitrogen deficiency is indicated by light-green leaves, but its excess delays the growing season, increases stem diameter, and causes lodging. Phosphorus stimulates root development at the start, while potassium is responsible for the formation of bast bundles and fiber quality. On limed soils, flax often suffers from boron deficiency, which causes the fiber to become coarse and brittle.

Nutrient	Share of total uptake by the beginning of flowering, %
Nitrogen (N)	up to 85
Phosphorus (P)	65–80
Potassium (K)	70–90

Seed treatment before sowing and optimal field operation timing

Protection of the future harvest begins 2–5 days before sowing with seed coating (pelleting). This method allows for the reliable attachment of preparations to the seed surface, reducing their application rate and ensuring the safety of seedlings. For seed treatment, preparations such as Vitavax, Vitaros, Maxim, Lamador, Phenoram Super, Royalflo 42S, and other approved fungicides are used.

Introducing additional components into the tank mixture significantly improves protection efficiency. The addition of Merkuran reduces seedling damage by flea beetles and wireworms by 2 times. The application of a complex of microelements during coating reduces the toxic effect of excess calcium in the soil, helping to obtain high-quality, flexible fiber.

Sowing begins immediately after the soil matures, once it warms up to the seeding depth seeding depth of 6–8 °C. Flax seeds are capable of germinating at a temperature of 3–5 °C, and young seedlings can withstand short-term frosts down to −3…−4 °C without losses. The optimal temperature regime for plant growth and development lies within 15–18 °C. As a moisture-loving crop, it is especially in need of water during the budding and flowering phases, but excess moisture during ripening is dangerous due to lodging.

Early sowing provides the flax grower with important technological advantages. Plants manage to form true leaves before the mass emergence of the flax flea beetle and suffer less from pathogens. In addition, early crops mature at the optimal time, which allows for high-quality dew retting of the straw in August.

• Soil temperature for the start of sowing — 6–8 °C
• Frosts tolerated by seedlings — down to −3…−4 °C
• Optimal growth temperature — 15–18 °C
• Sowing dates in Belarus conditions — 1st decade of May
• Return interval in crop rotation — 5–6 years

Seeding rates, crop maintenance, and pest control

Plant stand density directly determines the yield and quality of flax products. The standard seeding rate ensures an optimal feeding area, but for an increased yield of long fiber, the crops are thickened. When calculating sowing parameters, it is important to strictly observe the seed placement depth and row spacing.

• Standard seeding rate — 100–120 kg/ha
• Thickened seeding rate — 140–150 kg/ha
• Stand density — 2.6–2.7 thousand plants per 1 m²
• Seeding depth — up to 3 cm
• Row spacing — 7.5–9 cm (4.5–5 cm is better)

Sowing is performed using narrow-row flax seeders. Under favorable conditions, crop seedlings appear on the 4th–6th day after sowing. During this period, flax grows slowly and shades the soil poorly; therefore, weeding is a mandatory maintenance measure. Without timely protective measures, weeds can reduce the yield of flax products by 15–20% on average, and up to 50% in cases of high field weediness.

The main danger during the seedling stage is the flax flea beetle, which destroys the cotyledons and the growing point. Hot and dry weather contributes to a sharp increase in the activity of this pest. Agrotechnical practices (compliance with crop rotation, timely autumn ploughing, and early sowing) reduce the threat but do not guarantee complete safety. To control the pest 1–2 days before emergence, perform edge spraying of the field to a width of 30–50 m using insecticides such as Decis, Fastak, Sumi-Alpha, Karate, or Buldock.

In the event of mass pest outbreaks, crops are treated with insecticides at a dose of 0.5 to 1.5 kg/ha with a water consumption of 300–800 l. During this period, flax can be infested by both specialized pests (flax flea beetle, flax bollworm, flax thrips) and polyphagous ones (crane fly, silver Y moth, flour mite). For weed control, herbicides 2M-4X and Dicotex-80 are used. The choice of preparations must strictly comply with the "Catalog of Pesticides and Fertilizers Permitted for Use in the Republic of Belarus," taking into account the species composition of weeds in a specific field.

Protection against diseases is just as important as weed control. Every year, crops are affected by Fusarium wilt, anthracnose, Septoria leaf spot (pasmo), as well as calcium chlorosis, which develops in over-limed soils with a deficiency of boron and zinc. To prevent harvest losses, it is necessary to carry out preventive measures in a timely manner.

1. Observe crop rotation and return flax to the same field no earlier than 6–7 years later.
2. Apply balanced, optimal doses of fertilizer for the crop.
3. Carry out thorough cleaning and chemical seed treatment of the seed material.

During the growing season, to combat diseases, crops are sprayed during the "fir tree" and budding phases with one of the fungicides: benomyl, fundazol, derozal, or kolfugo super. This helps to stop the spread of infection in the early stages. The use of fundazol provides a pronounced economic effect, increasing fiber yield by 10–12%.

Harvesting dates and flax maturity phases

The timing of harvesting operations depends directly on the economic purpose of the crops. The condition of the stand, leaves, and seeds determines the readiness of the flax for harvesting. There are four successive phases of crop maturity, each of which has its own technological features.

• Green maturity (green flax). The stems and capsules remain green, and the leaves begin to turn yellow only in the lower third of the stem. The seeds are soft, in the milk stage of maturity. The fiber is already formed, but its elementary fibrils are not yet filled. Harvesting in this phase yields fine, shiny, but less durable fiber, which is used for the production of cambric or lace.
• Early yellow maturity. The stem stand acquires a light yellow hue. The leaves in the lower third of the stem turn brown and fall off, the rest turn yellow and wilt, and the green color remains only at the top. The capsules are covered with green veins, and the seeds reach waxy maturity (yellow or brown color). The fiber in this phase is soft, silky, and quite durable. The seeds ripen in the capsules during the drying of the pulled flax and are suitable for sowing and technical purposes.
• Yellow maturity. Occurs 5–7 days after early yellow maturity. The entire field turns yellow. The leaves of the lower half of the stem turn brown and fall off, and the upper ones turn yellow and wither. The capsules turn yellow and brown, the seeds inside them harden and acquire a light brown color. The fiber in the lower part of the stem begins to coarsen and lignify.
• Full maturity. The stems and capsules turn brown, and the leaves fall off almost completely. The seeds are fully ripe, hardened, and rattle when the capsules are shaken. The fiber over-ripens, lignifies, loses elasticity, and becomes stiff and dry.

After flax pulling with flax pullers or flax combines, the stage of primary processing of raw materials begins. The main task at this stage is to correctly distribute the straw flows and prevent the loss of the harvest. Threshing of fiber flax is carried out in two ways: either the capsules are combed and flattened, or they are flattened directly on the stems, separating the seeds from the resulting heap.

1. Additional sorting: the straw is separated by quality before the start of threshing.
2. Threshing: seeds are extracted using one of two technological methods.
3. Sending for processing: the threshed straw is immediately sent to the flax mill, for retting, or for field curing.

During the retting process, pectin-degrading bacteria (in the water method) or fungi (in the dew method) lyse the pectin substances that bind the fiber to the woody part of the stem. The preservation of the fiber's structure and the strength of the future fiber depend on the correct selection of the regime. The speed of this process directly depends on the chosen retting method.

Retting type	Duration
Cold water	10–25 days
Warm water	3–6 days
Chemical	a few hours

The final stage of obtaining raw fiber is the mechanical separation of the wood (shive) from the bast part. First, the stems are passed through breakers to crush the shive, and then the obtained raw material is cleaned of its residues on scutching machines. The quality of the finished long scutched fiber is assessed according to GOST. The higher the assigned fiber number, the lower its consumption will be for the production of one square meter of fabric.

Economic importance of cotton

Cotton firmly holds first place in global consumption of spinning raw materials. In CIS countries, it is traditionally called "white gold" due to its exceptional national economic importance. The fiber serves as a basic raw material for the cotton and cellulose industries.

The spheres of application for cotton fiber depend on its length:

• Long-staple cultivars: used for the production of cambric, marquisette, tracing paper, tire cord, as well as high-grade sateen, chintz, and fustian.
• Blended fabrics: fiber is mixed with wool for the production of fine semi-woolen fabrics.
• Short fiber: used for the manufacture of special jersey, decorative and linen fabrics, blankets, and waffle towels.

Linter — the fuzz from seeds and short, broken fiber — is processed separately. It is used to produce:

• medical cotton wool and bandages, technical wicks, and artificial felt;
• cellulose, collodion, cellophane, and celluloid;
• artificial silk, photographic and cinematographic film, lacquers, and paper;
• gunpowder for military purposes.

Cotton seeds make up about 65% of the total weight of harvested raw cotton. This is a vital by-product of crop processing, rich in vegetable fats. The oil obtained is used in the food industry for canning and margarine production, and is also sent to soap factories as a technical raw material.

Indicator	Value
Seed oil content	18–27 %