Linum usitatissimum (Flax) Cultivation

Cultivation
Propagation is usually by seed. Flax may also be propagated vegetatively from stem cuttings. Seed is recovered from fiber crop. Plump and disease-free (resistant to flax wilt) seed should be selected. All dirt, chaff, and shrunken seeds must be removed as they may carry disease. Chemicals may be used to treat the seed before planting. Sow seed 1520 days before the last average killing frost data of the area, which is the same date as for sowing spring wheat. In Minnesota and North Dakota, flax seed sown in April or early May yields best. In Texas, flax is fall-sown in November or early December, and fits well into rotations with cotton, sudangrass, grain sorghum or vegetables. Rate of sowing seed varies from 3 kg/ha for seed production to 160 kg/ha for fiber production. Seed sown in rows 11.5 to 75 cm apart in various countries, depending on whether plant is grown for fiber (closer) or seed (each plant given more room). In some sections flax and spring wheat are seeded together and the resulting threshed crop separated by screening with a fanning mill. Yields are increased and weeds are better controlled by seeding with a mixture of 2 or 3 pecks of wheat seed with 2845 kg of flaxseed per hectare. Flax germinates at a lower temperature than many of the grassy weeds that may become troublesome later. A well-prepared firm seedbed will ensure sowing at the proper depth and this will result in prompt and uniform germination. Flax should be sown at depth of 2.53.2 cm with a grain drill rather than with a broadcast-seeder. However, in some countries, seed is broadcast and harrowed in. Fall plowing flax fields is preferable as it allows soil to settle. Soil should be packed by rolling, disking, harrowing and surface leveled before planting. In Texas fall-sown flax is used to eradicate Johnsongrass from fields as the flax grows while the Johnsongrass is dormant and takes over the area so the Johnsongrass cannot get a foothold. Flax responds well to irrigation, especially light irrigations as it is a shallow-rooted crop. When crop begins to ripen, irrigation should be withheld to hasten maturity. If soil is kept wet, blooming,may continue indefinitely. Total water applied usually 9,00012,000 cu m/ha; 110 irrigations may be necessary per season. Very little added N is needed, only 20 kg/ha, except in irrigated California crops where need for all fertilizers in higher. Compared with other crops, flax requires relatively small amounts of nutrients. In other countries, such as Sweden, a complete NPK fertilizer is used, 300400 kg/ha; in The Netherlands, 2040 kg/ha of N used, and P and K added as required. Heavy manuring can produce heavy yields, but there is an accompanying fall in the quality of the fiber. The aim in fertilizing is to improve the yield without causing corresponding fall in quality. Direct organic manuring should be avoided when fiber flax is grown on well-cultivated soils that are amply supplied with nutrients. Organic manures, such as farmyard manure, are best applied to the preceding crop. Microelements may be needed on a particular soil, and should be added after a soil test. Various rotation plans are followed in different countries in which 611 years intervene between flax plantings on a given piece of land.

Harvesting
Most flax cvs mature in 90120 days, but some winter-planted cvs require more than 200. Flax seed may be harvested in the same manner as wheat. Probably two-thirds of the crop is combined, and may be harvested with a grain binder, with a swather (windrower) or by direct combining which is the cheapest method and is entirely satisfactory, when the flax is thoroughly dry and free of weeds. Care in threshing necessary to prevent cracking of seed for propagation. Maturity of flax is judged by the color of the bolls (seed capsules) rather than by the color of the straw. Crop ripe enough to harvest when 90% of bolls have turned brown, although crop can be pulled at beginning of seed ripening, since immature seed bolls mature after harvest and produce viable seed. Static electricity is sometimes a problem in harvesting, and may occur at high temperatures (38C) and low humidities. Seeds cling together and to combine; screens may get clogged and serious seed loss can result. Harvest must be delayed until humidity increases slightly or temperature is low enough to prevent it. For storage, seed must have a low moisture content, 810%. When crop is grown for the fiber, it is harvested with a special pulling machine or may be pulled by hand as is done in Europe; machines are still not entirely satisfactory. The pulled flax is shocked in the field until dry, when the seed is threshed in such a way as to prevent the breaking of the straw. Stems are harvested when the lower two-thirds of stem have turned yellow and the leaves have fallen from it, about 1 month after the appearance of first flowers. Straw is then retted, by bacterial fermentation, to remove gums and resins from the fiber. Retting may be simple exposure of the straw to the weather for 23 weeks, depending, on weather; it may take up to 8 weeks, or until the dew and rains have removed the resins and the fiber is loosened, or more complicated methods of soaking in water for about a week under specific regulation of time and temperature. It can also be done chemically, but these methods cost more. When straw has been properly retted, it is dried, broken and scutched to separate the fiber from the bark and stems, after which it is baled and is then ready to be manufactured. Fibers are about 50 cm long average, but may vary from up to 1 m. Flax fibers are in the cambium layers of the plant, and are bast or phloem fibers. They occur in bundles in the pericycle; each bundle containing about 1040 individual fibers. Each stem contains about 30 fiber bundles forming a ring around the stem. Retted flax contains about 64% cellulose, 17% hemicellulose and 2% lignin. Before straw is retted, seed capsules are removed, (called "rippling"), usually by machine. One ton of fiber flax yields 100 kg of seed. It is possible to extract fiber from flax straw without retting, (called "green flax"). After straw is deseeded, it is taken directly to the breaker and the scutcher. This fiber has a considerable amount of extraneous matter attached, making it necessary to degum before spinning the fiber. This method usually results in a higher production of short tow fiber than there is with retted flax fiber.

Yields and Economics
Fiber yields run 2001200 kg/ha. Seed production figures underate seed yields of 220 to 2820 kg/ha, but locally yields can be much higher. Record seed yields in the U.S. range from 2460 kg/ha in the northern States to 4390 kg/ha for winter sowings in Arizona/California (Dybing and Lay, 1981). According to Agricultural Statistics 1981, yields of flaxseed per harvested acre range between 7.913.7 bushels per acre (roughly 25.4 kg/bushel) with the average farmers price of $2.38 to $9.67 per bushel. Production figures for most countries fall under 1 MT/acre = 2.5 MT/ha, but in 1980 Mexico, Uruguay, and Egypt exceeded this. Flax straw average yields range from 57 MT/ha. As indicated by the use of flax for fiber and linseed oil, this crop is and has been for a long time, a very important crop in the economics of many nations. It is grown in many countries as an important crop. In the United States it is grown in the North Central States and in the Imperial Valley of California. For flax seed, the main producers are Argentina, United States, Canada, USSR, India, and Uruguay; for flax fiber, USSR (6570% of world production), France, Poland, Belgium, The Netherlands. The major consumers are United Kingdom (imported 37,000 tons of flax fiber and tow in 1968), West Germany, Italy, France, and Belgium. Present world production 725 thousand MT fiber grown on 1,729,000 ha.

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