In the current process of welsh onion cultivation, due to unreasonable aspects such as chemical fertilizers, pesticide application and management techniques, there have been cases where the planting area has increased but the yield and quality have decreased. The nine factors that are not conducive to the high yield of green onions and the corresponding control measures will be sorted out for the reference of the majority of onion growers.
1. Severe diseases caused by various diseases According to the survey, it is generally more than 15 years that the continuous cropping of scallions is heavy. The diseases of tinea sclerophylla, root rot, verticillium wilt, purple spot and so on have different degrees of occurrence in different growing stages of scallion. , directly affect the quality and yield of green onions. Control measures: (1) Green onions must be planted with onions and garlic for 3 to 4 years, which can effectively reduce the occurrence of pests and diseases. (b) Increase the use of fully cooked organic fertilizers, focusing on the use of nitrogen, phosphorus, potash fertilizers, and trace element fertilizers. (c) Deep ploughing of onion fields before winter, followed by winter irrigation.
Second, improper use of herbicides in the onion fields with 48% trifluralin EC closed the ground for weeding, if the method is not correct or the concentration is too high, the dose is too large, will affect the normal growth of small onion seedlings, but also cause the emergence of not Qi or not emergence. If 2,4-D EC is used in adjacent plots of onion fields, the liquid will drift to the onion fields and will inhibit the normal growth of small onion seedlings. In the plot of continuous cropping of wheat and onions, excessive use of 2,4-D EC or use of herbicides in the former barley fields will inhibit the normal growth of scallion seedlings in the onion field. Prevention and control measures: 33% of Shitian's cream can be used for weeding, 200 ml/mu, 50 to 60 kg water, spraying on the surface and closing the ground. As far as field herbicides are concerned, Shitian's supplements are safer and more effective. When herbicides are used in wheat fields, do not use drugs in windy weather. When there is no wind, ultra-low or directional spray methods should also be adopted to avoid the liquid floating to the onion fields. After the occurrence of phytotoxicity, remedial measures can be taken. Each 15 kilograms of water plus a raindrop on the 1st of the spring to add a solution to the damage, spray once every 3 to 5 days, and spray 2 to 3 times. Herbicides and antidotes can also be used to relieve phytotoxicity.
Third, the soil phosphorus element is too high, potassium deficiency, basal fertilizer, top-dressing irrational use onion fields only pay attention to the use of monoammonium phosphate, while ignoring the other elements of the input, especially the severely heavy land mass, can lead to phosphorus in the soil Excessive accumulation, soil compaction, inhibition of absorption of potassium, iron, zinc, copper and other elements of Welsh onion, resulting in imbalance in the proportion of nutrient elements, directly affect the quality and yield of green onions. The application of basal fertilizer and topdressing fertilizer is unreasonable, which can lead to excess of nitrogen, and the proportion of large, medium and trace elements is seriously out of balance. Prevention measures: (1) After soil testing, according to the phosphorus content of soil nutrients and the laws of phosphorus and potassium needed by welsh onions, determine the basic and recovery rates of phosphorus and potassium fertilizers; increase the use of trace element fertilizers. Basal nitrogen, phosphorus, potassium three elements should be 1:0. A ratio of 17:1.1 was used to match the organic fertilizer application. (2) Calculating the production of 5000 kg of fresh onions per acre with fertilizers, 6 kg of phosphorous elements, 13 kg of diammonium phosphate, 20 kg of potassium and 40 kg of potassium sulfate. It requires a one-time application of diammonium phosphate, potassium sulfate can be part of the base application, part of the topdressing. (C) pay attention to increase organic fertilizer, the general application of organic fertilizer per acre of 3000 to 5000 kg, the use of phosphorus in phosphate fertilizer is better. Topdressing should use nitrogen or potassium fertilizer combined with compound fertilizer or compound fertilizer. Generally, the proportion of nitrogen and potassium fertilizer is 1:0.3 to 1:0.4.
Fourth, the time for seedling cultivation is too late, and the time for transplanting is delayed. When the seedlings are sowed in spring, many farmers always sow when the temperature rises. The purpose is to make the onion seedlings stand up and be unearthed, which will save labor, labor, and land. In fact, this obviously shortens the growth cycle of green onions. If transplanting is delayed, it will be difficult for welsh onions to achieve high yields. In the field comparison, late-growing and late-planting green onions are 30% to 50% lower than the early-growing and early-planting onion fields under the same fertilizer and water conditions. Control measures: There is a close relationship between welsh onion high yield and early nursery and early transplanting. The onion sowing time is generally from March 5 to May 20. It can also be said that as long as the surface thawing is more than 5 centimeters, it can be planted, and it should be sooner rather than later. After the onion sowing, it should cover the mulch in time, and after emergence, it must control the watering. Onion seedling height 30 ~ 40 cm, diameter 1 ~ 1.5 cm thick, that is suitable for transplanting seedlings. Generally transplanting in the early June to early July should be late as soon as possible. Before the onset of the rainy season and the high temperature, the onion seedlings should be returned to green earlier, and the roots should form large roots earlier to lay a good foundation for the onion high yield.
Fifth, the depth of planting is too shallow and the height of earth is not enough. The farmer said that "deep green onion and light garlic" means that welsh onions must be planted deeply. The height of the lush green onions depends on the nature of the congenital species; on the other hand, it depends on the management of the fertilizer and the height of soil cultivation. It can be seen that soil cultivation also plays an important role in the high yield of welsh onions. Prevention and control measures: scallion colonization depth of 7 cm, can not be buried in the heart. Soil cultivation is an important measure to soften onion sheaths, prevent lodging, improve quality and yield. Practice has shown that the higher the soil, the longer the light blue, the lighter white tissue is also more white and full. The height of soil should be based on the height of light blue growth. After each soil cultivation, the soil should be tamped to prevent it from collapsing after rain or watering. Pay attention to soil should be carried out in the afternoon, to avoid the dew in the morning, when the humidity in the field, so as to avoid light blue, broken leaves and cause rot.
Sixth, the row spacing is not standardized, and the arrangement of the ridges to the unscientific short variegated varieties should adopt narrow rows of shallow ditch planting. When the long onion-white variety is less demanding on the light blue, narrow rows of shallow trenches can also be planted; when the quality and yield requirements are high, wide rows and deep trenches are used for planting. The plant spacing should also be determined according to the species, and cannot be generalized. There are many unfavorable factors in the east-west direction of onion ravine, which will affect the high yield of green onions. Prevention and control measures: The direction of the ditch and ridge should be north-south, so that the entire onion field is evenly distributed. This will reduce the fall of green onions caused by strong north winds in autumn and winter. In particular, heavy rain and windy weather, such as digging ridges to the east-west direction will cause the entire onion fields to fall flat. The spacing of the rows is based on the arrival of Bao Yezi and the five leaves. For example, the spacing is 60-65 cm and the spacing between the rows is 6-7 cm.
Seven, onion crops are not scientific, pest control is not timely Welsh onion diseases mainly include root rot and downy mildew; insect pests are rootworms and leaf miners are the most dangerous, if not timely and effective prevention and cure, welsh onion is difficult to achieve high yield . Prevention and control measures: Prevention should be the main method, and comprehensive prevention and control should be the principle. Commonly used agents for preventing and treating diseases: 75% of chlorothalonil 600 times, 50% of dexamethasone 600 to 800 times, 50% of carbendazim WP 300 times, and 50% of thiophanate powder 500 times liquid. General pest control agents: 50% of phoxim 1000 times, 2.5% of deltamethrin 3000 times, 2.5% of kungfu in 3000 times, 48% of 2500 times of emulsion . The above agents can be used alone, or they can be mixed and used alternately to prevent spraying once every 7 to 10 days and eradicating once every 3 to 5 days.
Eight, watering time is not reasonable If the water supply is sufficient, it is beneficial to adjust fertilizer with water and accelerate the growth of onion. However, it is not the better the moisture content. For example, when it is hot and rainy season, excessive water in the onion fields will cause severe occurrence of root rot of green onions. Failure to master the law of water requirement and watering time of green onions at various growth stages will affect the output of Welsh onion. Prevention and control measures: Drainage and irrigation works should be done well before welsh onion planting, drainage after rain should be timely, to prevent heavy rain filling the onion ditch, silt eyes, resulting in lack of oxygen onion root system, resulting in decay, and cause other diseases. After wilting onion and returning to green, it is generally not watered (except for dry years) in late July. In the middle and early August, the weather turns cool, light blue is in the initial stage of growth, the temperature is still high, and the water requirement is not high. Watering should be reduced. If the watering should be done in the early morning, do not water at noon, so as to avoid a sudden drop in ground temperature, affecting the growth of green onion roots, this period generally need to water 2 or 3 times. After the summer heat, the average daily temperature dropped below 24°C until the frost falls. The green onions enter the peak of growth. This period is when the weight of leaves and scallions of onion swiftly increase. The water requirement increases greatly and should be poured every 4 to 5 days. , And the amount of water should be large, long onion ditch or uneven green onion field C to build earthworms, so that the amount of water per ditch and uniform. Generally green onion leaves are upright, leaf color is light green, surface wax is thin, and the tube filled with glue indicates sufficient water; if the green onions are wilting, the leaves are drooping, the dark green leaves are dark, there is shrinkage, and the wax powder is thickened Slight water shortage; if the onion leaves yellow-green leaves, dry tip, thin and drooping leaves indicate severe water shortage. After the frost falls, the temperature drops, the onion basically grows into the light blue period, the water requirement decreases, but the soil needs to be kept moist, so that the slush is grouted, the leaves are hypertrophied, filled with glue, and not loose. This period can be watered 2 times. . Stop watering 10 days before harvest to facilitate harvesting and transportation.
Nine, the "onion is not wang" nutrition and reproductive growth habits are unfavorable factors Scallion in the growing season, if the disease by the pests and diseases, sustained high temperature, defertilization, dehydration and other factors, no matter how to strengthen management, shallots are not There will be a second peak of growth, which can generally reduce production by 30% to 70%. Prevention and control measures: (a) scientific and rational application of basal fertilizer, top dressing. (b) Prevention and control of pests and diseases should be based on prevention and integrated prevention and control. (c) Select herbicides and use them properly. (D) According to the different growing season of green onion, different water requirements for reasonable watering. (5) Timely drainage and cultivating after rain, in order to increase the air permeability of roots of Welsh onion. (6) Adding related foliar fertilizers in the liquid medicine for controlling pests and diseases will be conducive to robust growth of green onions and increase the ability of drought resistance, resistance to stigma, heat resistance and stress resistance of onion strains.
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