Most flax cvs mature in 90–120 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 (38°C) 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, 8–10%. 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 2–3 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 10–40 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 200–1200 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 7.9–13.7 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 5–7 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 (65–70% 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.
Return to Main Menu