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1. Institute of Millet Crops, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang 050035, China; 2. Cereal Crops Research Laboratory of Hebei Province, Shijiazhuang 050035, China; 3. National Foxtail Millet Improvement Center, Shijiazhuang 050035, China; 4. National Engineering Research Center of Semi-arid Agriculture, Shijiazhuang 050000, China

Abstract Quinoa (Chenopodium quinoa Willd.) is native to South America, and its grains are mainly used. In recent years, using quinoa seedlings as a vegetable have become more and more popular. In this paper, the biological characteristics, nutritional ingredients and health functions of quinoa were introduced in detail, and on the basis of experiments and production, a set of scientific cultivation techniques was summarized to promote the large-scale cultivation of this characteristic vegetable.

Key words Quinoa, Characteristic vegetable, Health food

1 Introduction

Quinoa (ChenopodiumquinoaWilld.), native to the Andes in Bolivia, Ecuador, Chile and Peru in South America, has more than 5 000 years of planting history and is the main traditional food of the Inca indigenous inhabitants. It is called the "mother of food", "mother of the grain" and "the real gold of the Andes" by the Incas. Its grain and seedlings can be eaten. Quinoa is recognized worldwide for its high nutritional value and many development and utilization values. The United Nations Food and Agriculture Organization (FAO) believes that quinoa is the only single plant that meets the basic nutritional needs of the human body, and officially recommends it as the perfect nutritious food[1]. In 1987, quinoa was first introduced to China, and the planting area has been increased gradually since 2010. With the cultivation of quinoa, the edible value of quinoa seedlings has been more and more widely recognized, and quinoa is also rich in nutrients. In this study, the characteristics of quinoa were studied firstly, and based on experiments and production, a set of scientific cultivation techniques was summarized to promote the large-scale cultivation of this characteristic vegetable[2].

2 Biological characteristics

2.1 Morphological characteristicsQuinoa is an annual herbaceous dicotyledon of the genusChenopodium, Amaranthaceae. It is an allotetraploid with 36 chromosomes. The roots are straight roots, and the main root is developed and coarser, while the lateral roots are less developed; the plants are branched; the leaves are like duck feet, and the leaf margins are corrugated; the young leaves are green, and some have purple or red[1].

2.2 Growth habitsQuinoa is tolerant of cold, drought, salt and alkali, and frost. It can grow when relative humidity is 40%-80% and temperature is 0-38℃. The optimum planting temperature is 14-20℃, and it can be tolerant of mild frost (-1.0-0℃). It can also grow when soil pH is 5.5-8.5. It grows well in sand loam and loam, and can also grow in the limit soil with poor drainage and low natural fertility[1].

3 Nutritional ingredients and health characteristics of buckwheat

Quinoa contains protein, fat, carbohydrate, crude fiber, carotene, vitamin B1 and B2, Vc, and various inorganic elements such as calcium and iron. It also contains volatile oil, alkaloids, and so on. In addition to being as food, it can be used as medicine. It is cool in nature and sweet in taste, and has medicinal effects of clearing heat, detoxicating, lowering blood pressure, and clearing damp[3].

3.1 Amino acidsThe total amino acid content of fresh quinoa can reach 2.38%, and that of dried quinoa is as high as 26.16%. Among them, the content of essential amino acids accounts for 48.52% of total amino acids, mainly containing 12 kinds of essential amino acids: histidine, isoleucine, leucine, lysine, cystine, threonine, phenylalanine, methionine, valine, arginine, tyrosine, aspartic acid, glutamic acid, serine, proline, glycine, and alanine[4].

3.2 FlavonoidsQuinoa contains flavonoids, and the content of flavonoids in dried quinoa is 12.41 mg/g. Flavonoids have many effects and strong resistance to oxidation. They can improve bone health, stimulate the secretion of osteoprotegerin, and remove oxygen free radicals from the body, and the ability to prevent oxidation is more than 10 times that of VE. Besides, they can slow down cell degradation and aging, reduce the incidence of cancer, and have certain health effects on people with high blood pressure and high blood fat[5].

3.3 VitaminsQuinoa contains VA, VB, VC, VD, VE, VKand other vitamins. Among them, it is abundant in VCand VA, and the content is 0.292 and 0.038 mg/g respectively. VCcan improve immunity and prevent cardiovascular disease. VAcan protects the retina and then vision, and prevents cataract. VEcan promote sex hormone secretion in men and women, prevent female abortion and improve fertility[6].

3.4 Mineral elementsQuinoa is very rich in mineral elements, including Ca, Na, Mg, K, Fe, Cu, Zn , Al, P, Mn, Co, Ti , Cr and other essential mineral elements. Therefore, eating more quinoa can effectively alleviate the deficiency of trace elements. The trace elements such as zinc (Zn) and manganese (Mn) in quinoa have the effects of improving immunity and preventing cancer. It also have a certain health care function for middle-aged and elderly people with calcium deficiency[7].

3.5 Plant fiberQuinoa contains a large amount of soluble fiber. Eating quinoa can promote intestinal peristalsis, prevent constipation, improve intestinal flora, and improve rectal cancer, appendicitis, hemorrhoids, varicose veins of lower extremities and other diseases. It can make people feel full, help obese people to lose weight, and be used as diet food. For diabetics, it can improve sugar tolerance and regulate blood sugar level[8].

4 Cultivation techniques

4.1 Cultivation seasonIn a plain, quinoa seedlings can be planted all year round. Since quinoa likes cold, it can be planted in spring and autumn, and the best sowing time is from April 5 to May 20 or from August 15 to September 15. If it is planted in summer, it is necessary to use a sunshade to avoid exposure of quinoa seedlings to strong sunlight, and measures such as irrigation and ground cooling should be paid attention to. In winter, it should be planted in a greenhouse.

4.2 Soil preparation and fertilizationThe plots planted with quinoa seedlings should have fertile soil and convenient irrigation and drainage. The base fertilizer of quinoa is applied once when quinoa seedlings are planted. Before the sowing of quinoa seedlings, 45-60 m3/ha of decomposed organic fertilizer and 375-450 kg/ha of ternary compound fertilizer (the ratio of N, P and K is 15∶15∶15) are mixed well and broadcast to be as base fertilizer. Afterwards, deep tillage is conducted at a depth of 20-25 cm, and soil is leveled and harrowed to improve soil physical properties and cultivate soil fertility.

4.3 GerminationQuinoa seeds are soaked in warm water at 35-50℃ for 6-8 h. When it is planted in spring, autumn and winter, the seeds can be directly sown after being soaked in warm water, and do not need to be refrigerated. In comparison with the seeds refrigerated, the germination time and germination rate are not much different. However, when it is planted in summer, the the germination of the seeds that are not refrigerated is obviously later than that of the seeds refrigerated, and the germination rate is lower. Therefore, if it is planted in summer, it is best to refrigerate the seeds for 3-4 h at (5±2)℃ after the seeds are soaked in warm water.

4.4 SowingThe germinated quinoa seeds are mixed with the cooked cereal seeds at a ratio of 2:1 and then sown. A plot of land is watered well before sowing, ditched and sown. The ditch depth is 2-4 cm, and the row spacing is 15-20 cm. They are covered with fine soil (0.5-1.0 cm) after sowing, and the amount of quinoa seeds sown is 30.0-37.5 kg/ha.

4.5 Watering and topdressingIt is generally not necessary to water quinoa seedlings before emergence, and it is necessary to keep the soil moist after emergence, which is conducive to the growth of quinoa. When a quinoa plant has 2-3 true leaves, soil should be loosened shallowly to weed and preserve soil moisture. In the seedling stage, quinoa plants grow slowly, and base fertilizer can generally meet their. When the seedlings have 5-6 true leaves, topdressing (150-225 kg/ha of ammonium sulfate) and watering are performed. The growth period of quinoa is short, and enough nitrogen fertilizer can make the plants grow vigorously and achieve high yield.

4.6 Prevention and control of plant diseases and insect pests

After quinoa seeds are sown, a pesticide is mixed with bran or soil and then scattered on the sown seeds to prevent cockroaches and other underground pests from harming the seedlings. Quinoa has fewer pests and diseases, and pesticide is not used throughout the growth period. In the early stage of downy mildew and anthracnose, it can be sprayed with 75% chlorothalonil solution diluted by 600 times and 50% carbendazim solution diluted by 700 times. For aphids, rapeseed meal, and leaf miner, it can be sprayed with 10% imidacloprid solution diluted by 2 000 times or 2% avermectin solution diluted by 2 500-3 000 times. The use of pesticides is stopped 10 days before harvesting.

4.7 Timely harvestingQuinoa can be harvested many times after being sown one time. When the height of the seedlings is above 15 cm, the harvesting can be started in batches. The big seedlings are harvested firstly and evenly, so that the remaining plants have substantially equal nutrient areas and grow sufficiently to prolong the harvest period and increase the yield. The general harvest period is 30-60 days after sowing.