Flax

Economic importance

The stem of flax contains 20–30% bast fiber, and in highly productive varieties even more. Flax fiber is characterized by high technological properties: strength, flexibility, fineness, etc. It is twice as strong as cotton fiber, three times as strong as wool, and inferior only to silk.

Flax fiber is used to produce household, technical, container, and packaging fabrics. From 1 kg of fiber, 10 m² of batiste or 2.4 m² of linen, 1.6 m² of technical fabrics, or 1 m² of tarpaulin are produced. Linen fabrics are wear-resistant and resist rotting. They are in demand throughout the world.

In fabric production, flax fiber is considered one of the best components when used together with chemical fibers.

Flax seeds contain 35–42% by seed weight of a well-drying oil, which is used in the production of paints, varnishes, drying oil, in the soap-making, paper, electrical engineering, and other industries, as well as in medicine and perfumery. A minor part of flaxseed oil is used for food purposes.

Flax cake serves as a good concentrated feed for livestock. 1 kg corresponds to 1.15 feed units. It contains 6–12% fat and up to 30 (36)% digestible protein.

When retted straw is processed into fiber, short spinning fiber (tow) is obtained, used for making sack and packaging fabrics, as well as non-spinning fiber (tow), which is used for making ropes, twine, and as caulking material. Shive (stem wood) serves as raw material in the production of cardboard, ethyl alcohol, acetic acid, acetone, and other materials; it is used for the production of building boards (shive boards) and insulating materials.

Stem wood can serve as organic fertilizer and be used as fuel.

Flax has medicinal importance.

The share of flax straw in the fiber flax harvest is 70–75%, and with high yields about 80%. Seeds account for 10–15% (up to 30% in seed-growing crops) and chaff for 10–15%. The yield of retted straw from the flax straw harvest averages 70%.

History

Flax is one of the oldest agricultural crops. It was known in India, China, Egypt, Mesopotamia, and Transcaucasia 4–5 thousand years BCE. It is assumed that the homeland of this crop is Southwestern and Eastern Asia, as well as the Mediterranean.

On the territory of Russia it was grown in ancient times. As early as the 12th century, flax was grown in the Novgorod and Pskov principalities. Fabrics and other products were made from flax, which were used not only to satisfy their own needs but also for exchange. In the 15th century, the volume of exports of flax fiber and seeds to other countries reached large proportions. In the 16th century, the first rope factory was built in Russia. In 1711, Peter I issued a decree on expanding flax crops, and somewhat later a decree appeared on flax seeding rates. At the same time, state linen factories were built, producing wide linen cloth for sails and other needs. Until the end of the 18th century, flax fiber occupied first place among Russian goods intended for export.

On the world market, Pskov, Novgorod, Kashin, and Kostroma flax were especially famous. At the beginning of the 20th century, the Russian Empire was the main supplier of flax fiber.

Before the widespread introduction of sunflower in the Russian Empire, oil flax served as the most important source of vegetable fat and feed cake.

Cultivation areas and yields

The area sown to fiber flax in the world in the mid-1980s was 1.5 million ha, with more than 70% of the world area (1.06–1.1 million ha) concentrated in the USSR.

Significant sown areas exist in the Netherlands, Belgium, France, England, Germany, Czechia, Slovakia, Poland, Romania, and on limited areas also in Canada, the USA, and Japan.

The area sown to oil flax in the world was 1.06 million ha. The USSR accounted for 10% (90 thousand ha) of the world areas. Large areas were in Argentina, the USA, Canada, and India.

Fiber flax is grown in Russia in areas with a humid and moderate climate; oil flax in drier and warmer areas. The main crops of fiber flax are located in the Non-Chernozem zone (Tver, Smolensk, Yaroslavl, Vologda, Pskov, Kostroma, and other oblasts), as well as in Belarus, Ukraine, and the Baltic countries.

In the early 2000s, the area occupied by fiber flax in Russia was 120 thousand ha. From 1970 to 2000, sown areas sharply decreased: in 1970 — 727 thousand ha; 1980 — 595 thousand ha; 1990 — 418 thousand ha; 2000 — 108 thousand ha. The gross harvest of flax fiber also sharply decreased: from 207 thousand t in 1971–1975 to 52 thousand t by the early 2000s.

Oil flax crops in Russia are located in the Central Chernozem zone, the Volga region, Western Siberia, as well as in Kazakhstan, the steppe part of Ukraine, Tajikistan, Uzbekistan, Kyrgyzstan, and Armenia.

The yield of flax fiber in 1976–1980 in the USSR averaged 3.4 dt/ha, in 1984 — 3.8 dt/ha. In terms of gross flax fiber harvest, the USSR occupied first place in the world. The maximum yield was obtained in Pochinkovsky district of Smolensk oblast (1983) on an area of 9 thousand ha and amounted to 7 dt/ha of fiber and 4 dt/ha of seeds.

Botanical description

The genus Linum of the family Linaceae (Linaceae) includes more than 200 species, which are distributed in temperate and subtropical regions of all parts of the world. These are mainly annual, sometimes perennial herbaceous plants.

On the territory of Russia and the countries of the former USSR, 40–45 flax species occur. Among them, common cultivated flax — Linum usitatissimum L. — is of agricultural importance.

According to modern classification, common flax is divided into five subspecies, of which only 3 are of greatest importance in Russia:

• Mediterranean subspecies — subsp. mediterranium Vav. et Ell. Plants are short (up to 50 cm). Flowers, capsules, and seeds are large. Weight of 1000 seeds is 10–13 g. Cultivated in Mediterranean countries.
• Intermediate subspecies — subsp. transitorium Ell. Plants of medium height (50–60 cm). Flowers, capsules, and seeds are medium-sized. Weight of 1000 seeds is 6–9 g. Distributed as an oilseed crop in southern Ukraine, Crimea, Transcaucasia, and Kazakhstan.
• Eurasian subspecies — subsp. eurasiaticum Vav. et Ell. Plants varying in height and branching. Flowers, capsules, and seeds are small. Weight of 1000 seeds is 3–5 g. The most widespread subspecies in cultivation. Cultivated in Europe and Asia.

The Eurasian subspecies is also divided into 4 groups of varieties:

• Fiber flax (elongata). Tall (from 60 to 120 (175) cm) single-stemmed plants, branching only in the upper part. Stems are light green or grayish green. Leaves are lanceolate, sessile. Flowers are regular, pentamerous, with blue, pink, or white petals. Five stamens with blue, orange, or yellow anthers. Pistil with a five-locular ovary and five styles. Fruit is a five-locular capsule, divided by septa into ten half-locular cavities. One seed develops in each half-locular cavity. Seeds are flat, ovate, brown or brownish. On one plant, depending on sowing density, 2–3 to 8–10 seed capsules are formed. The root system of fiber flax is poorly developed, consisting of a main taproot and fine delicate branches located in the upper soil layer, mainly in the arable layer.
• Fiber flax is cultivated in areas with a moderately warm and humid climate.
• Curly flax, or horned flax (var. brevimulticaulia). A short (30–50 cm) plant with a strongly branching stem at the base and a large number of capsules (from 30–35 to 50–60 or more). Seeds are larger than those of fiber flax. Weight of 1000 seeds is about 8 g. Cultivated for oil production in the countries of Central Asia and Transcaucasia.
• Intermediate flax, or intermediate flax (var. intermedia). Plants of medium height (50–70 cm), 1–2-stemmed. Usually there are more capsules than in fiber flax (10–25). More often cultivated for oil, less often for oil and fiber, in the Central Chernozem zone (Kursk, Voronezh oblasts), in the Volga region (Samara oblast, Bashkortostan and Tatarstan), partly in Siberia, Ukraine, the North Caucasus, and Kazakhstan.
• Creeping flax (var. prostrata). Plants with numerous stems creeping until flowering. By the beginning of flowering, the stems rise and reach a height of 100 cm or more. Cultivated as a winter crop on limited areas in Transcaucasia.

Flax forms determine the directions of cultivation: dual-purpose — for fiber and seeds (fiber flax) and seed-purpose (curly flax). Intermediate flax occupies an intermediate position, usually approaching curly flax. In Russia, over 85% of all flax crops are fiber flax, or spinning flax.

Technological properties of flax fiber

In the stems of fiber flax, 20–30% is fiber, which consists of cellulose (88–90%), pectin (6–7%) and waxy (3%) substances, and ash (1–2%). The share of fiber in the lower part of the stem is only 12%, and its quality is low (thick, coarse, partly lignified). In the middle part of the stem, the fiber share reaches 35% and is distinguished by higher quality (fine, strong and long, with the smallest internal cavities and thick walls). In the upper part of the stem, the amount of fiber decreases to 28–30%, and the quality is somewhat worse (the fibers have a larger lumen and thinner walls).

Bast fibers are located in the parenchyma tissue of the stem bark in the form of fibrous or bast bundles, which consist of many individual cells called elementary fibers.

Elementary fibers are elongated cells with pointed ends, 15–40 mm long and on average 20–30 µm thick. The fibers are firmly glued by pectin into a fibrous bundle. Each bundle may contain 25–40 fibers. The fibrous bundles are arranged in a ring, 25–30 bundles along the periphery of the stem. The bundles, joining with each other, form a band of technical fiber.

The length of the bast bundles is determined by the total length of the stem and its technical length, that is, the length from the trace of the cotyledon leaves to the beginning of branching (the first branch of the inflorescence). Tall stems more than 70 cm long have a greater technical length, contain longer elementary fibers and longer technical fiber. Thin stems (1–1.5 mm) give fiber of higher quality, since their elementary fibers have thick walls and a relatively small internal cavity, which makes it possible to obtain strong and flexible fibers.

The quality of flax fiber is characterized by technological properties: strength, flexibility, fineness, luster, elasticity, softness, purity, soundness, and spinning ability. The overall assessment of fiber quality is determined by comparing the fiber with standard references. The higher the number of flax fiber, the less it is consumed to produce 1 m of fabric. High-quality fiber should be long, thin-walled, without a large cavity, smooth, and clean.

Biological characteristics

Vegetation

The following development phases are characteristic of flax:

• emergence;
• beginning of stem elongation (“fir-tree”);
• budding;
• flowering;
• ripening (sometimes subdivided into fruit formation, seed ripening, full ripeness).

Under favorable conditions, flax seedlings usually appear 5–6 days after sowing.

In the emergence phase, the flax plant has two cotyledon leaves with a small bud between them. In the “fir-tree” phase, the plant reaches a height of 10 cm, with 5–7 pairs of true leaves formed on the stem. These two phases (about 1 month after emergence) are distinguished by slow stem growth in height but rapid development of the root system.

Then flax enters a period of intensive plant growth in height (increments of 3–5 cm per day). This period lasts 12–20 days and ends with the beginning of budding, at which plant growth slows to 0.5–1 cm per day and almost stops by the end of flowering. All agronomic practices aimed at inhibiting this process lead to elongation of the stem and improvement of fiber quality.

During ripening, rapid lignification of plant stems and formation of seeds in capsules occur.

According to data from the Department of Crop Production of the MAA named after K. A. Timiryazev, for the variety Svetoch, the period from sowing to emergence is 6–7 days. The “fir-tree” phase begins 26–28 days after sowing, budding — after 54–56 days, flowering — after 60–62 days. The growing season lasts on average 82–84 days. For various varieties, the growing season is from 70 to 100 days.

Crop rotation

When using high and intensive agrotechnologies for cultivating fiber flax, the preceding crops can be winter cereals, grain legumes, potato, maize, sugar beet, and the layer or turnover of the layer of perennial grasses.

In Western Europe (Belgium, the Netherlands, etc.), clover is considered a poor preceding crop for flax, since due to excess nitrogen it lodges, and the straw becomes coarse and branching.

Frequent return of flax to its former place in crop rotation leads to accumulation in the soil of harmful microorganisms and specific weeds, which affects yield. This phenomenon is called “flax fatigue.” It is returned to its former place after 7–8 years.

Intermediate crops of the family Brassicaceae (rapeseed, colza, oil radish, etc.), which are used as green manure or for green fodder, are of important agronomic importance. These crops are sown after harvesting early cereals.

Fiber flax is considered a good preceding crop for winter and spring cereals, buckwheat, beets, and potatoes.

Good preceding crops for oil flax are fallow land, the layer of perennial grasses, winter cereals, maize, grain legumes, melons, and other row crops.

Fertilizer system

Flax has high requirements for soil fertility. Thus, according to numerous data from the All-Russian Flax Research Institute and other experimental institutions, when applying complete mineral fertilizer, the yield of fiber flax straw increases by 0.4–0.8 t/ha or 40%, and seeds by up to 30%. In addition, the quality of flax fiber improves.

Flax uses mineral fertilizer nutrients differently: easily hydrolyzable nitrogen is assimilated by about 30–90%, phosphorus by 10–25%, potassium by 26–40%; from the soil, respectively: nitrogen — 20–30%, phosphorus — 6–13%, potassium — 12–13%. Under conditions of sufficient moisture in the soil, it is recommended to take the upper gradation.

Nitrogen helps increase the content of long fiber in the harvest. However, its excess lengthens the growing season of plants, leads to lodging of crops, and increases susceptibility to diseases, which ultimately noticeably reduces yield and fiber quality. Flax plants are especially sensitive to nitrogen deficiency in the “fir-tree” phase, and the greatest demand occurs during the “fir-tree”–budding period.

Phosphorus is very important in the period from emergence to the “fir-tree” phase (5–6 pairs of true leaves). Sufficient phosphorus nutrition accelerates ripening and increases the yield of seeds and fiber. When choosing forms of phosphorus fertilizers, it is necessary to take into account their effect on increasing soil acidity, to which flax is very sensitive.

Potassium helps increase the number of elementary fibers in the stem, increases the yield and quality of flax fiber, reduces the risk of plant lodging, and mitigates the negative effects of excess nitrogen fertilizers. The greatest demand for potassium occurs in the first 3 weeks of plant growth and in the budding phase.

The removal of nutrients with 1 t of straw and seeds averages 10–14 kg of nitrogen, 4.5–7.5 kg of phosphorus, and 11–17.5 kg of potassium.

On sod-podzolic soils, the increase in straw yield is 5–7 kg per 1 kg of a.i. of fertilizer.

When developing a fertilizer system for flax, it is necessary to take into account the weak ability of the root system to assimilate nutrients from the soil and the high sensitivity to high concentration of the soil solution, as well as the short growing season.

Applying 30–40 t/ha of manure together with phosphate rock (400–600 kg/ha) and potassium chloride (150–200 kg/ha) under the preceding winter or row crops increases yield by 25–30%. As green fertilizer, lupine, serradella, vetch, and rapeseed can be used, which are grown in post-harvest crops. Manure and composts are not applied directly under flax, as this leads to lodging of crops.

According to recommendations of the All-Russian Flax Research Institute, for flax following spring cereals (barley, oats, spring wheat), with their planned grain yield up to 2.5 t/ha, 30 kg of nitrogen (or 100 kg/ha of ammonium nitrate) is applied. After cereals with a planned yield from 2.5 to 3.5 t/ha, it is recommended to apply 20–25 kg of nitrogen (or 60–70 kg of ammonium nitrate). With a planned grain yield of more than 3.5 t/ha — 15–17 kg of nitrogen (or 50 kg/ha of ammonium nitrate).

When placing flax after clover with a hay yield of 3.0–4.0 t/ha, it is recommended to apply no more than 15–17 kg of nitrogen under flax, and with a hay yield of 4.5–5.0 t/ha, nitrogen under flax is not recommended. The rate of nitrogen application on drained peatlands is reduced, while phosphorus and potassium are increased.

The recommended ratio of nutrients in complete mineral fertilizer for flax is NPK — 1 : 2 : 3 on soils poor in nitrogen, and 1 : 3 : 4 on soils rich in nitrogen; on weakly cultivated soils — 1 : 2 : 2, on medium cultivated — 1 : 3 : 3, on highly cultivated — 1 : 4–6 : 4–6.

In addition to ammonium nitrate, urea, ammonium sulfate, or compound fertilizers — nitroammophoska, nitroammophos, and ammophos — can be applied under flax. 100 kg of nitroammophoska corresponds to N_12–15P_12–15K_12–15, nitroammophoska — N ₁₆P ₁₆K ₁₆ (NPK ratio 1 : 1 : 1), ammophos — N _11–12P _36–52. The application rate of compound fertilizers per 1 ha is determined by nitrogen, and the missing amounts of phosphorus and potassium are supplemented with superphosphate and potassium chloride.

Under flax, in addition to simple superphosphate, double superphosphate (P _34–45) and boron superphosphate containing 19–20% phosphorus and 0.2–0.3% boron can be used.

For rational use of mineral fertilizers, the All-Russian Flax Research Institute recommends applying nitrogen, phosphorus, and potassium under flax taking into account their content in the soil and the planned yield of flax products (table). At the same time, the recommended fertilizer rates must be adjusted taking into account zonal features.

On strongly acidic soils with pH less than 5.0, it is better to replace superphosphate with a mixture consisting of three parts phosphate rock and one part superphosphate, and on medium acidic soils (pH 5.5) — a mixture of equal parts phosphate rock and superphosphate.

Part of the total rate of phosphorus fertilizers is applied at sowing in rows in the form of granulated superphosphate at the rate of 50 kg/ha on commercial crops and 20 kg/ha on seed-growing crops.

Of potassium fertilizers, potassium chloride (56–60% K₂O), potassium sulfate (48% K₂O), and potassium salt (30–40% K) can be applied under flax. On sandy loamy soils with magnesium deficiency, it is advisable to apply potassium magnesia (K₂O 28–30% and MgO 8–10%).

To correct the developed zonal average fertilizer rates for flax, the ARRI FAS recommends using correction coefficients taking into account the planned harvest and nutrient content in the soil.

Nitrogen fertilizers are applied under flax in spring, potassium and phosphorus — in autumn, before autumn plowing or immediately after it. On soils with a low content of mobile forms of phosphorus and potassium, as well as on heavy cohesive soils, phosphorus-potassium fertilizers are recommended to be applied in two doses: half in autumn, before autumn plowing, and the second half in early spring, before spring soil treatment.

The main mineral fertilizer is applied broadcast using special fertilizer seeders with disc-type sowing apparatus RTKh-4.2A. Granulated superphosphate is applied at sowing in rows with combined seeders SZL-3.6.

Top dressing during plant vegetation gives a good effect. Ammonium nitrate or ammonium sulfate can be used for top dressing. The consumption rate is N_20–30, superphosphate — P30–40, potassium chloride — K30 or compound fertilizers. Top dressing begins when plants are 6–8 cm high or 20 days after emergence. Delay in nitrogen top dressing can lead to stretching of the flowering duration and uneven ripening. Often top dressing is done only with phosphorus fertilizers.

Of micronutrients, flax is most in need of boron. Boron datolite or boron-magnesium fertilizer is applied in spring before cultivation at the rate of 20–30 kg/ha (Vavilov; according to other recommendations 40–70 kg/ha of boron, Kolomeychenko). In addition to these fertilizers, when boron is deficient in the soil, boron superphosphate can be used in rows at sowing in an amount of 50 kg/ha. Boron reduces the negative effect of lime on flax plants and reduces plant damage by bacterial diseases. Boron fertilizers are recommended to be applied on limed, podzolic, and waterlogged soils, as well as during the development of new lands.

Copper micronutrients should be used when growing flax on peatlands at the rate of 25 kg/ha of copper sulfate or 250–500 kg/ha of pyrite cinders.

Sod-podzolic soils of the flax-growing zone, characterized by increased acidity, are subject to liming. Experiments of the All-Russian Flax Research Institute showed that when lime is applied directly under flax in small amounts, the yield of flax fiber increases, but its quality noticeably deteriorates. Joint application of lime and boron somewhat eliminated the negative effect of lime. For this reason, liming of acidic soils in flax crop rotations is carried out under the cover crop of red clover or in the fallow field. The following rates of lime application are recommended at:

• pH 4.5 and below — 2.5–3 t/ha;
• pH 4.6–5.0 — 2–2.5 t/ha;
• pH 5.0–5.5 — 2 t/ha.

Lime is applied using mineral fertilizer spreaders 1RMG-4, RUM-8. Gaps when applying mineral fertilizers are not allowed; deviations from the specified application rate should be no more than 10%.

A good effect is given by additional application of wood ash under flax in addition to mineral fertilizers: for every 100 kg of fiber, 100 kg of ash.

Manure or peat-manure compost is usually not applied directly under flax, as this can lead to lodging of plants, unevenness, and weediness of crops. However, under conditions of intensification of flax growing, the role of organic fertilizers in flax crop rotation increases. According to research, manure and composts in flax crop rotation are optimally applied in two fields — under potato or other row crops and under winter or spring cereals with undersowing of perennial grasses. In this case, mineral fertilizers should be applied under crops annually.

According to data from the All-Russian Flax Research Institute, to ensure high yields of all crops included in flax crop rotation, it is necessary to apply annually on cultivated sod-podzolic soil at least 10–13 t/ha of organic fertilizers and 1 t/ha of standard mineral fertilizers.

The application of organic (20 t/ha of manure) and mineral (N ₃₀P ₄₅K ₄₀) fertilizers under oil flax significantly increases yield. In this case, phosphorus-potassium fertilizers are applied under autumn plowing, and nitrogen fertilizers under pre-sowing cultivation. At sowing, it is also recommended to apply superphosphate or nitroammophoska in rows at the rate of P15–20, which increases the yield of oilseeds by 0.3 t/ha.

Soil cultivation system

Sowing

Crop care

Care for commercial fiber flax crops consists of:

• post-sowing rolling;
• harrowing (when a crust forms);
• control of weeds and pests.

The listed agronomic measures are carried out taking into account specific conditions.

Harrowing to destroy the soil crust is carried out with light sowing, rotary, or net harrows, as well as ring-spur rollers.

In addition to agronomic measures, the most important methods of crop care include the use of chemical means of controlling weeds, pests, and diseases of flax. The damage they cause to fiber flax can reach 30% or more in some years.

According to data from the All-Russian Flax Research Institute, the presence of more than 200 dicotyledonous weed plants per 1 m² of crops leads to a decrease in yield even with fertilizer application.

To control annual dicotyledonous weeds (white goosefoot (Chenopodium album), field pennycress (Thlaspi arvense), hemp-nettle (Galeopsis speciosa), field spurry (Spergula arvensis), wild radish (Raphanus raphanistrum), etc.), spraying with herbicides of the 2M-4X type, 2M-4X 80%, which are applied in an amount of 0.6–1.2 kg, is carried out. The consumption of working solution when spraying with boom sprayers ON-400 or others is 200–300 l, with aircraft — 150–200 l/ha.

The optimal phase of flax crop development for herbicide treatment is plant height from 5 to 8 (15) cm (“fir-tree” phase). During this period, leaves are located on stems at an acute angle (10–30°) and are often covered with a waxy coating, thus the negative effect of the herbicide on cultivated plants is noticeably reduced compared to treatment at later dates.

The greatest effect from spraying crops is achieved in clear and dry weather at an air temperature of 15–17 °C. Cool weather (12 °C) slows the penetration of the herbicide solution into weeds, while dry and hot weather enhances it, but at the same time causes wilting of flax.

According to data from the All-Russian Flax Research Institute, the use of herbicide 2M-4X (0.75 kg/ha) in a mixture with ammonium nitrate (9 kg/ha) or urea (13 kg/ha) promotes good flax growth and more complete cleaning of crops from weeds. Joint use of herbicide and nitrogen fertilizer compared to treatment with herbicide alone increases the yield of flax seeds by 13–14% and fiber by 12.8–27.7%.

According to data from the Department of Crop Production of the MAA named after K. A. Timiryazev, the effect of spraying crops with herbicide 2M-4X (0.5 kg/ha) in a mixture with ammonium nitrate (12 kg/ha) is enhanced if micronutrients are added to the mixture (boron 0.25 kg/ha, zinc and molybdenum 0.1 kg/ha each). At the same time, the fiber yield increases by 1.5–2 dt/ha, seeds by 1.3–1.5 dt/ha. Such joint action of herbicide, ammonium nitrate, and micronutrients is associated with increased plant photosynthesis. In addition, infestation of flax with bacteriosis, fusarium, rust, and other diseases noticeably decreases.

Particular attention in flax-growing farms should be paid to the control of couch grass (Elytrigia repens), which on heavily infested areas can reduce the yield of flax fiber by 20–25% or more. To control this weed, sodium trichloroacetate (TCA) is used. The preparation is applied no later than the first half of September, as “awl” shoots of couch grass appear after stubbling the soil from under grain crops or disking the layer of perennial grasses. The consumption rates of sodium trichloroacetate on sandy loamy soils are 20 kg/ha a.i. (or 23 kg/ha of 90% preparation), on loamy soils — 30 kg/ha a.i. (or 34.5 kg/ha of 90% preparation). The same doses are used after autumn treatment.

According to the results of experiments of the All-Russian Flax Research Institute, application of 30 kg/ha of sodium trichloroacetate before plowing leads to the death of 78.1% of couch grass rhizomes, and the increase in fiber yield reaches 13.6%, seeds — 10.8%.

Another malicious weed of flax is flax darnel (Lolium remotum). Against it, the herbicide 40% triallate is used, which is applied 1–3 days before sowing or on the day of sowing before leveling the soil surface with harrows at the rate of 1.5–2.5 kg per 1 ha. Triallate reduces contamination of flax seeds with darnel by 90–96%.

Care for flax crops should include plant protection from pests, primarily the widespread flax flea. Against the flea, 1–2 days before emergence, edge and blockade treatments of crops are carried out with insecticides to the width of 3–4 aggregate passes. For treatment, the preparation phosphamide Bi-58 is used in an amount of 0.8 kg/ha. For these purposes, 80% chlorophos (0.8 kg/ha) can also be used.

When the number of flax flea is more than 10 individuals per 1 m² in dry and hot weather or more than 20 individuals per 1 m² in wet weather, treatment is performed using boom sprayers. Liquid consumption is 200–300 l/ha.

To control thrips, crops are dusted with 12% HCH dust (15–25 kg/ha) after the “fir-tree” phase.

Harvesting

The ripening phase in fiber flax is divided into four phases:

• green;
• early yellow (early);
• yellow;
• full.

Green ripeness (green flax) occurs after flowering ends. During this period, stems and capsules are still green; only leaves in the lower third of the plant begin to dry and turn yellow. When seeds are crushed, a milky liquid is released from them. Harvesting flax in the green ripeness phase gives fine and shiny but weak fiber. Such fiber can be used in the production of fine products (batiste, lace).

In the early yellow ripeness phase, leaves of the lower half of the plant stem fall off, the rest, except the apical ones, turn yellow. Green veins remain on the capsules. Seeds in the capsules acquire a green-yellow color and a yellow tip (waxy ripeness). Harvesting flax in this phase allows obtaining fiber of the best quality: soft, silky, and strong.

In the yellow ripeness phase, all leaves become yellow, only those at the top of the stem remain; capsules acquire a brown color, seeds — light brown. It usually occurs 5–7 days after the early ripeness phase. Fiber quality in the yellow ripeness phase begins to decline. The fiber of the lower part of the stem becomes coarse.

In the full ripeness phase, all leaves fall off, stems and capsules become brown. Fiber collected in this phase is of low quality: dry, hard, inelastic.

For timely harvesting of flax, desiccation can be used. This technique allows drying plants on the root and eliminating field drying and ripening of plants in sheaves. Desiccation is carried out in the early ripeness phase.

Harvesting fiber flax with combines usually begins 2–3 days after the onset of the early yellow ripeness phase (Karpets, 1984). Flax harvested during this period allows obtaining the greatest amount of long fiber of high quality. By this time, seeds are sufficiently formed and after ripening can be used for sowing (technical ripeness of flax).

Harvesting flax in the yellow ripeness phase is carried out when obtaining seeds of breeding varieties of fiber flax in seed-growing farms. In the full ripeness phase, oil flax is harvested.

The period of technical ripeness of fiber flax is 8–10 days, but in hot weather it may be shortened. Therefore, delay in pulling leads to significant yield losses: on average, for each day, fiber losses are 2–3%, seeds — 1.5%.

According to data from the Flax Growing Experimental Station of the MAA named after K. A. Timiryazev, harvesting flax at the end of the yellow ripeness phase led to a decrease in the yield of long fiber on average over 5 years by 14.2% compared to harvesting in the early yellow ripeness phase, and harvesting in the full ripeness phase — by 21.9%.

Flax harvesting is considered the most complex and labor-intensive work in flax growing — it accounts for 70–80% of all costs. Therefore, the use of effective flax harvesting technologies has important production and economic significance.

The traditional sheaf harvesting method, including pulling, field drying of sheaves in shocks, threshing on threshers, and manual spreading on the meadow, does not meet the tasks of flax growing development. A more progressive and effective method of harvesting flax is the well-developed and many-years-tested combine method.

The combine harvesting method allows performing several operations: pulling, combing seed capsules, loading the heap into transport vehicles, binding flax straw into sheaves using a binding apparatus for subsequent delivery to the flax plant (combine LKV-4A) or spreading it on the flax field in a strip to obtain retted straw (combine LK-4A).

Compared with the sheaf method, the combine method shortens flax harvesting time by 3–4 weeks, and labor costs — when spreading straw on the flax field by 1.5–1.7 times or when delivering straw in sheaves by 3–4 times. The efficiency of the combine harvesting method increases when using several combines.

According to data from the All-Russian Flax Research Institute, preparing flax retted straw on the flax field is almost comparable to the process of its retting on meadow retting grounds. Conditions on the flax field can be improved by undersowing perennial grasses under flax (meadow fescue, perennial ryegrass, white clover, etc.). The quality of retted straw in this case increases by 1–2 numbers.

When harvesting flax with combines LK-4A, straw is spread on the retting ground simultaneously with harvesting in optimal agronomic terms — 20–30 days earlier than with the sheaf method.

During the retting of straw, approximately every 8–10 days it must be turned using mounted turners OSN-1 for uniform retting and to prevent overgrowth of retted straw with grass. Lifting of retted straw begins when its moisture is no more than 20%.

Lifting flax retted straw with binding into sheaves is carried out with a mounted picker PTN-1. The use of the picker reduces labor costs compared to the manual method by 6 times.

With the combine harvesting method, a wet heap is obtained, which consists of 52–84% capsules, 2–7% seeds, 12–16% tangled fiber and other impurities. The moisture content of the heap is usually high — 60–65%, seed capsules 40–50%. To prevent spoilage of seeds in capsules, the heap is evenly loaded into drying sections with a layer of 1.1 m in floor dryers or 0.7 m in conveyor dryers and immediately dried to a surface moisture of 16–18%, using installations, for example, OSV-60 with air heater VG1T-400 or VPT-600. The temperature of heated air should be no higher than 45 °C. After 20–45 hours of drying, cold air is blown for 1.5–5 hours to reduce seed injury during heap processing. The following requirements are imposed on drying and processing: loss of seed germination should be no more than 2%, crushing — less than 1%, irreversible losses during processing should be no more than 3%. Threshing of the heap is carried out on a thresher-winnower MV-2.5A. Seed moisture before threshing should be 10±2%.

In fiber flax cultivation, bringing the seeds obtained during harvesting to sowing conditions is of great importance. For this, farms clean them on grain-cleaning air-screen machines SM-4, SOM-300, and electromagnetic machine SMSH-04. At flax seed stations, flow lines from a complex of machines and equipment for processing and preparing seeds for sowing are used for this.

Compliance with the technology of drying seeds intended for sowing is important, since loss of germination occurs due to death of the embryo under the influence of heating temperature above the maximum permissible. The sensitivity of the embryo to high temperatures increases with increasing seed moisture. For shaft-type dryers, optimal drying regimes have been determined (table).

Flax straw may remain on the farm for primary processing or be immediately delivered to procurement points and flax plants. For delivery to flax plants, straw must meet established requirements (GOST). Sheaves must be round or oval in shape with a diameter of at least 13 cm. Straw moisture (to absolutely dry mass) must be 19%; straw with moisture more than 25% is not accepted by flax plants. Permissible contamination is 5%; with contamination more than 10%, straw is also not accepted.

The quality of flax straw is determined by length (handful length), strength, bast content, suitability, color, and stem diameter. Depending on these properties, it may have the following numbers: 5.00; 4.50; 4.00; 3.50; 3.00; 2.50; 2.00; 1.75; 1.50; 1.25; 1.00; 0.75; 0.50. The quality of delivered straw is assessed in daylight by comparing selected samples with seasonal standard samples.

Industrial technology of fiber flax cultivation

The All-Russian Flax Research Institute, together with the Ukrainian Research Institute of Agriculture and the Belarusian Research Institute of Agriculture, developed an industrial technology for cultivating fiber flax, which has been introduced on more than a quarter of all commercial crops. The technology is designed to obtain at least 5.5–8 dt/ha of flax fiber and 5 dt/ha of seeds, in addition to reducing labor costs by more than 2 times.

The industrial technology includes:

• concentration of fiber flax crops in the farm in 2–3 crop rotations;
• placement of flax after grain crops;
• application in crop rotation of scientifically based rates of mineral and organic fertilizers;
• main soil cultivation of the semi-fallow type;
• improved pre-sowing soil treatment;
• sowing in optimal dates with seeds of classes I and II with a seeding rate of 18–22 million/ha of germinating seeds;
• application of an integrated system of measures to control diseases, pests, and weeds;
• pre-harvest desiccation;
• mechanized harvesting;
• sale of at least 50% of the harvest in the form of straw according to the “field–plant” scheme. At the same time, as the experience of the All-Russian Flax Research Institute has shown, roll harvesting technology deserves attention.

Organizational measures are based on contracting and the creation of harvesting-transport complexes for harvesting flax in optimal terms and reducing losses of flax products.

Technological operations are recommended to be performed with machines for:

• seed treatment PSSH-5, PS-10A, OPSH-15;
• fertilizer application — POU, RTT-4.2A, 1-RMG-4, LDG-10A, LGD-15A, BDT-3, PLN-8-40, PLN-4-35, PLN-3-35, KPS-4-03, ZKVG-1.4, RVK-3.6;
• sowing — SZL-3.6;
• harvesting — LK-4A, LKV-4A, PTN-1, OSN-1, PNP-3, PSP-3, VPT-600, TLN-1.5A, T-25A, MTZ-80, TAU-1.5, MV-2.5A, ML-2.8P, trailer 2PTS-4M.

Thus, intensive technology, using intensification factors, and despite significant capital costs during the development of the technology, allows the most rational use of resources and obtaining flax products with greater efficiency.

For example, on the Bolshevik collective farm in Torzhok district, using industrial flax technology in 1983, 9.2 dt/ha was obtained from a total area of 330 ha, with labor costs for obtaining 100 kg amounting to: seeds — 12.2 man-hours; straw — 2.5 man-hours; retted straw — 5.3 man-hours.

Features of oilseed flax agronomy

Oil flax is placed in crop rotation after fertilized winter crops, perennial grasses, grain legumes, maize, potato, and other crops.

Autumn cultivation is carried out as early as possible, before which soil stubbling is recommended. The main tasks of spring treatment include preserving moisture in the soil and controlling weeds.

When fertilizing oil flax, phosphorus and potassium fertilizers (30–45 kg/ha of phosphorus and potassium each) are applied under autumn soil cultivation, nitrogen (25–30 kg/ha of nitrogen) — under pre-sowing cultivation. According to data from the All-Russian Research Institute of Oil Crops, a good result is obtained by applying granulated superphosphate in rows at sowing. Seed yield increases by 2.9 dt/ha.

Oil flax is sown simultaneously with early spring crops. The sowing method is ordinary row or narrow-row. On weedy soils, wide-row sowing with 45 cm row spacing is used. The seeding rate is from 30 (for wide-row) to 80 kg/ha. For dual-purpose use of flax (for seeds and fiber), the seeding rate is increased by 10–15 kg. Sowing depth is 4–5 cm.

Harvesting oil flax for seeds begins in the full ripeness phase. Harvesting is carried out with grain combines. For dual-purpose use of the harvest — in the yellow ripeness phase with a cutting height of 10 cm and a reduced number of drum revolutions per minute to 800–1200. If flax straw is to be spread on the flax field, the bottom of the harvester is removed from the combines. If the straw is to be spread elsewhere, the combine collects the straw into heaps and then it is transported to meadows and distributed over the surface in a layer of no more than 15 cm. In wet and warm weather, flax stems can ret in 10–12 days.

Fiber is separated from retted straw using breakers and scutchers (construction tow). To isolate spinning fiber, the tow preparation machine KL-25A is used.

References

• Vavilov P. P., Gritsenko V. V., Kuznetsov V. S. et al. (1986). Plant Growing. Edited by Vavilov P. P. 5th ed., revised and enlarged. Moscow: Agropromizdat.
• Kolomeychenko V. V. (2007). Plant Growing/Textbook. Moscow: Agrobusinesscenter.
• Niklyaev V. S. (2000). Fundamentals of Agricultural Production Technology. Agriculture and Crop Production. Moscow: “Bylina.”