Soil hardening will lead to slow growth of sweet potatoes, and it is difficult to increase production even if more fertilizer is applied. Deep tillage can deepen the living soil layer, make the soil loose and mature, enhance soil nutrient decomposition, improve soil fertility, increase soil water storage capacity, improve soil permeability, and be beneficial to stem and leaf growth and deep root development, thus increasing sweet potato yield.
If the soil structure is good, the organic matter content is high, or the topsoil is thick, it should be turned deep, but generally not more than 40 cm. Too much deep turning can easily lead to reduced production. Generally, the yield of 30 cm deep ploughing is about 20% higher than that of shallow ploughing 15 cm. It is advisable to plough deeply in sunny days, and avoid farming when the soil is sticky and wet, so as not to cause soil hardening. Deep tillage should be combined with applying organic fertilizer and increasing soil organic matter to improve soil physical and chemical properties and soil fertility.
2), ridging
Sweet potatoes are mainly planted on ridges. Ridge cultivation has the advantages of increasing the surface area of the ground, increasing the light receiving area, increasing the interface between soil and atmosphere, large temperature difference between day and night, and being beneficial to soil moisture reduction and drainage in the field. When ridging, try to keep the ridge spacing consistent. If the width is uneven, the adjacent plants will get different nutrients, which will cause the dominant plants to grow excessively, while the weak plants may not get enough sunlight and nutrients, and the uneven growth will affect the yield.
The ridging methods of sweet potatoes in Hainan vary widely, and each has its own advantages and disadvantages. One of the ridging methods is to level the ridge top when ridging. After planting potato seedlings, the soil on both sides of the ridge is slightly raised, and the middle is made into a ditch shape, which is beneficial to watering and drought resistance at seedling stage, convenient for fertilization on both sides, good in water and fertilizer conservation, and convenient for gradually covering the soil to control weevil in the middle and late growth stage. However, it should be noted that planting sweet potatoes in this way is easy to plant potato seedlings too deep, some as deep as10 cm; Secondly, it is easy to cover the potato pieces too deeply when covering the soil in the later stage. When the roots grow in the deep layer of the ridge, they are in a state of poor hardening, poor water and heat, and poor ventilation, which is not conducive to potato production and potato pieces expansion, resulting in low yield. In addition, most of the ridge spacing is too wide, and some of them reach 1.5m, which fails to make full use of the land. Due to the slow growth of sweet potato seedlings and the late enclosure, it is not conducive to drought resistance, and the slow enclosure causes more weeding workers. In addition, if the ridge spacing is too wide, the number of seedlings per mu is small, which is not conducive to high yield. It is an important link in sweet potato production to cultivate potato seedlings by using the germination characteristics of potato blocks. Potato chips should be varieties with many root scars and many buds, and 100 ~ 250g potato chips with good quality in summer and autumn should be selected as seed potatoes. Various seedling raising methods can be adopted, such as artificial heating hotbeds, various fire pits, or brewing hotbeds and electric hotbeds that use microbial decomposition to release heat energy. There are cold beds, hotbeds covered with plastic film in the open field and seedlings collected to use solar radiation for heating. Covering the seedbed with plastic film can increase air temperature and humidity, which is beneficial to seedling growth, increase seedling yield and increase the weight of 100 seedlings by about 20%. In the process of seedling raising, high temperature should be used to accelerate germination in the early stage. During the 10 days from sowing to complete emergence, the temperature gradually decreased from 35℃ to 28℃. When the seedling height is about 15cm, the temperature gradually drops from 30℃ to 25℃. The suitable water-holding capacity of bed soil is 70 ~ 80%, and the initial water is insufficient, the root system stretches slowly, the leaves are small and the stems are thin, which is easy to form old seedlings; Too much water and insufficient air affect germination; Under high temperature and high humidity, potato seedlings are delicate and grow in vain. The seedbed temperature must be kept at about 20℃ and the relative humidity is 60% within 3 ~ 5 days before picking seedlings. In order to avoid the high temperature in the film-covered seedbed, in addition to ventilation and heat dissipation, the bed soil should maintain a certain humidity to reduce the temperature in the film. In the process of germination, the nutrients needed by potato seedlings are mainly supplied by potato pieces. However, after root elongation or seedling harvesting for 2-3 times, nutrient soil or quick-acting nitrogen fertilizer should be applied. Loose bed soil and sufficient oxygen can strengthen breathing and promote metabolism. Severe hypoxia will suffocate seed potato cells and lead to seed potato rot. Be sure to pay attention to ventilation when covering with plastic film, which is conducive to the growth of strong seedlings.
Seedling raising time varies with different seedling raising methods. Generally, seedlings are raised in heated seedbed about 65438 0 months before sowing, and in cold bed and open field about 65438 0.5 months before sowing. The planting density should be 23 ~ 32kg potato chips per square meter. Pick seedlings in time to avoid affecting the quality of seedlings and the number of seedlings in the next crop. There are two ways to pick seedlings: cutting and pulling.
Cutting seedlings is more beneficial than pulling them out.
① There is no wound on the surface of the seed potato, which can prevent the invasion of germs;
(2) The seed potato will not damage the root of the potato due to shaking; ③ Promote the growth of basal axillary buds and small branches, and increase the number of seedlings. Cutting seedlings should be more than 3 cm away from the bed soil, and cutting vines can prevent diseases and increase production.
1), the variety should be pure.
Sweet potato production should try to use the same variety and seedling quality. When different varieties or superior and inferior seedlings are mixed, it is easy to reduce the yield, which is one of the main reasons for the low yield and poor quality of sweet potato in southern China. Because there are great differences between different varieties of sweet potato and between superior and inferior seedlings, some plants grow vigorously in the early stage, some grow slowly in the early stage, some varieties are tolerant to fertilizer, some varieties are barren, some varieties have long vines, and some varieties have short vines, so some plants gain advantages after mixed planting, and the growth of other vulnerable plants is affected by excessive nutrition. In addition, the stems and leaves of some dominant plants grow vigorously, which will lead to lower potato yield than normal. Generally speaking, even if two high-quality products are planted together, the output will be reduced.
2), strong seedlings
We should use strong seedlings and eliminate weak seedlings. The yield difference between strong and weak seedlings can reach 20~30%. Because strong seedlings return to seedlings quickly, the survival rate is high, the root system grows much stronger, and the ability to absorb nutrients is strong. It is required that potato seedlings should be strong, top-notch, short internodes and free from diseases and insect pests. If there is more milk when picking seedlings, it shows that potato seedlings are rich in nutrition and strong in vitality, which can be used as one of the indicators to diagnose the quality of potato seedlings. Generally, the length of potato seedlings should reach 20 ~ 25cm, and it is best to have 6 spreading leaves. Potato seedlings are too long, with many leaves, large transpiration area and late seedling return, while seedlings are too short, which takes a long time to reach the normal seedling length. Too long and too short are not conducive to high yield.
In order to cultivate strong seedlings, it is necessary to use potato pieces to raise seedlings. Generally, before transplanting 100 day, potato pieces with moderate size (200-300g for a single potato piece), uniformity, no pests and diseases and no wounds are selected as seeds. First, plant the seeds in a seedbed with a width of 65,438+0 meters. When the potato seedlings grown from potato blocks grow to 25-30 cm, seedling propagation is carried out, and when the number of seedling nodes reaches 6-65,438+00, topping is carried out to promote branching. 5 ~ 8 days before the planned planting, quick-acting nitrogen fertilizer should be applied thinly to cultivate seedlings and strong seedlings. When the potato seedlings grow to 25 ~ 30 cm, they should be harvested and planted in time. It is emphasized that the tender and strong seedlings should be used as seedling shears. When cutting seedlings, leave a few branches within the first 5 cm, but not too long. Starting from new seedlings, seedlings should be cut in cycles.
Try to use the first seedling and avoid the intermediate seedlings (second and third seedlings). The main reason is that sweet potatoes often carry black spot disease, root rot and nematode disease, and the germs carried in potato blocks will slowly move to the top of potato buds, while the top seedlings can largely avoid the germs carried by potato seedlings, because the moving speed of germs is lower than the growth speed of potato buds, and most of the germs stay near the base, and the upper potato seedlings are less likely to get sick. In some places, such as Hainan, farmers seldom use potato pieces to raise seedlings. For many years, they have been accustomed to using stems and vines to raise seedlings continuously, and some even use secondary seedlings, which leads to the degradation of sweet potato varieties and the decline of yield, which is one of the main reasons for the low yield of sweet potato in Hainan.
3) virus-free sweet potato seedling culture
Virus-free sweet potato is to remove virus from sweet potato by biotechnology, cultivate virus-free sweet potato seedlings, restore excellent varieties, and improve yield and quality. At present, the technology of "tissue culture and seedling raising" is mainly used to cultivate potato seedlings with virus-free stem tips in China. The main measures include rapid propagation of test-tube seedlings and cutting tender seedlings in soil.
4), sterilization and pest control
Sterilization: The main purpose is to prevent the occurrence of old seedlings caused by diseases. The method is to soak the 6~8 cm segment 10~ 15 minutes in 50 times of 40% carbendazim suspension solution or 700 times of 70% thiophanate methyl solution.
Insecticide: In order to kill the insect source of seedlings, pesticides such as dimethoate can be sprayed on the sweet potato fields ready for harvesting. Before planting, the head of sweet potato vine can be soaked with 500 times dimethoate 1-2 minutes. Generally, ridge tillage can deepen the soil layer, improve ventilation, accelerate the absorption and loss of heat, and has a large temperature difference, which is also beneficial to drainage and drought resistance. In areas prone to waterlogging and suitable for close planting in autumn, the yield of double ridges is higher than that of single ridge and small ridge. Timely early sowing can prolong the growth period and significantly increase the yield. When the soil temperature of potato in the main producing areas is stable at around 18℃ in spring and summer, the yield will be reduced by 1 ~ 1.5% every day after planting. Planting strong seedlings has the advantages of fast rooting, high survival rate and early potato production, and the yield of strong seedlings is more than 10% than that of weak seedlings.
Planting density varies with seasons, varieties and uses. There are 3000-5000 potatoes per mu in spring and summer, and 4000-6000 potatoes per mu in autumn and winter. Strive to reach the leaf area index of 3 ~ 4.5 at the peak of stem and leaf growth. Due to the continuous cutting of feed sweet potato stems and leaves, the density can be increased to 6000 ~ 8000 plants per mu under the condition of more fertilization.
1), planting time
The potato areas in summer and autumn in the south mainly include the southern part of Fujian, Jiangxi and Hunan provinces and the northern part of Guangdong and Guangxi. Summer potatoes are generally planted in May, and autumn potatoes are generally planted from early July to early August. The southern potato regions in autumn and winter include Hainan, southern Guangdong, Guangxi, Yunnan and Taiwan Province provinces. Autumn potatoes are generally planted in early July to mid-August, and winter potatoes are generally planted in165438+1October. Hainan can be planted all year round because of its superior climate, but it is better to grow sweet potatoes in rice fields in winter. Its advantages are: firstly, make full use of winter fallow fields, at this time, the climate gradually changes from hot to cold, which meets the requirements of the whole growth period of sweet potato and is conducive to starch accumulation in the later stage. Moreover, the soil of paddy-upland rotation is beneficial to the growth of sweet potatoes, reducing pests and diseases, and easily obtaining high-yield and high-quality sweet potatoes. Secondly, due to the off-season, fresh sweet potatoes can be sold to the mainland and exported to Japan and South Korea.
It is best to plant it when the soil is wet and dry on cloudy days and when the temperature is high in sunny afternoon. It is not suitable to plant sweet potatoes after heavy rain, and it is easy to form firewood roots. Should wait until the rain stops and the soil moisture is suitable before planting. It is not suitable for irrigation after planting. The survival rate of sowing after irrigation or heavy rain is high, but potato seedlings often grow poorly because the soil is saturated with water and the soil temperature is cold. At the same time, the soil becomes more compact, and the oxygen content in the soil decreases, which hinders the development of the root system and slows down its growth. If there is no rain for a long time, we can consider drought-resistant planting, digging holes and spraying water, covering with thin soil after the water dries, and stepping on seedlings after planting, so that the roots can be in close contact with the soil and survive early. If the seedlings are watered after planting, they need to be covered with dry soil to wet the surface.
2), reasonable close planting
Planting 2500~4000 plants per mu, in a certain density, the general yield increases with the increase of close planting degree, while the rate of large and medium-sized potatoes decreases with the increase of close planting degree. If it is used as food, you don't have to grow big potatoes, but you can harvest small and medium-sized potatoes properly and sell them well. Generally, the ridge width is 1 m, the ridge height is 25~35 cm, and about 3300 plants are planted per mu. Attention should be paid to the same plant spacing, and uneven plant spacing is likely to cause two plants that are close together to become weak plants.
3), planting method
There are many planting methods of sweet potato, mainly including the following five planting methods, and the horizontal planting method is generally the best, as shown in Figure 2.
Horizontal planting method:
The seedlings are 20~30 cm long, and the nodes planted in the soil are distributed in the shallow soil layer about 5 cm below the soil surface. The conditions of this method are basically the same, most nodes can take root and produce potatoes, few nodes are empty, and potatoes are numerous and uniform, which is suitable for plots with good water and fertilizer conditions. This method is often used in large-scale high-yield fields all over the country. However, its drought resistance is poor, and it is prone to lack of plants or weak seedlings when it meets unfavorable environmental conditions such as high temperature and drought and poor soil. In addition, due to the large number of tubers, it is difficult to ensure that each tuber has enough nutrition, which leads to a large number of small potatoes and affects the yield. If edible fresh potatoes are produced, more small potatoes will sell well.
Oblique insertion method:
Suitable for short seedling planting, seedling length 15 ~ 20cm, planting seedling about 10cm, seedling on the ground 5 ~ 10cm, potato seedling slope about 45 degrees. It is characterized by simple transplanting, large tubers on the upper node of potato seedlings buried in soil, small tubers on the lower node and uneven tuber size. Its advantages are good drought resistance, high survival rate, few and concentrated tubers per plant, and it is suitable for water-deficient mountainous areas and dry land. High yield can be obtained by proper close planting, strengthening fertilizer and water management and striving for large potatoes.
Bottom planting method:
The seedling base is 2~3 cm in shallow soil layer, and the middle node is slightly deeper in 4~6 cm soil layer. Suitable for plots with fertile soil, deep soil layer and good water and fertilizer conditions. Because there are many buried nodes, it has the advantages of both horizontal insertion method and oblique insertion method. The disadvantage is that the nodes buried deep in the soil, such as improper management or heavy soil, are easy to become empty nodes without potatoes, so be careful not to insert the middle nodes too deep, the sand can be deeper and the clay should be shallower.
Direct planting method:
Multi-purpose short seedlings are directly inserted into the soil and buried in 2~4 sections. Its advantages are high potato yield, drought resistance and quick seedling delay, and it is suitable for hillside fields and arid and barren plots. The disadvantage is that the number of tubers is small, and it is necessary to plant them closely to ensure the yield.
Cane insertion method:
Press all the top-cut potato seedlings into the soil, and the potato leaves are exposed to the surface. After planting, compact with soil and water. The advantages are that the damaged cutting tip can make the axillary buds of cuttings germinate early, sprout and branch step by step, take root and bear potatoes, and because the stems are leafy, the potatoes can grow bigger and bigger, and it is not easy to grow in vain. Disadvantages are poor drought resistance, labor-consuming, and only suitable for small-scale planting.
Precautions for planting
1), shallow planting. Because the soil layer with loose soil, good ventilation and large temperature difference between day and night is most conducive to the formation and expansion of potato blocks, it is advisable to bury potato seedlings in the deep part rather than in the deep part, and carry out shallow planting on the premise of ensuring survival. The shallow planting depth of wet soil should be 5~7 cm, and the deep planting depth of dry land should not exceed 8 cm.
However, under the conditions of strong sunshine and drought, it should be noted that if the planting is too shallow, the potato seedlings are difficult to take root because of the strong surface dryness and transpiration, and the stems and leaves are easy to dry up, resulting in seedling shortage. Measures such as proper deep planting should be considered.
2) Increase the number of potato seedlings buried in the soil. This is conducive to more potato seedlings, easy survival, more potatoes and high yield. The number of buried nodes should be combined with the planting depth, and the buried nodes should be buried in the soil layer which is conducive to the formation of roots, and the short seedlings of 20~25 cm are suitable, and the number of buried nodes is generally 4~6.
3) Keep potato seedlings upright after planting. The stems and leaves of upright potato seedlings are not in contact with the ground surface, so as to avoid high temperature burns on the ground surface after planting and form weak seedlings or dead seedlings.
4) In dry season, leaves can be buried for planting. When burying the soil, bury as many leaves as possible. The method of burying leaves has high survival rate and early seedling return, which is beneficial to increase production. Because of the large leaf area of sweet potato, its growth usually needs more water, especially after potato seedlings are planted. At this time, if most leaves are exposed to the soil surface, under the strong sunlight, their physiological adjustment needs a lot of water, while the newly planted potato seedlings have no roots, so it is difficult to absorb enough water only by the stems buried in the soil, which leads to the competition between leaves and stem tips, and the stem tips are in a withered state, delaying their return to seedling stage, and even leading to the death of potato seedlings in serious cases. Burying most leaves in wet soil can effectively solve the water supply problem of potato seedlings. Leaves can not only lose water, but also absorb water from the soil, so as to ensure that the stem tip can turn green and grow as soon as possible. In many places, a variety of sweet potatoes are planted in arid, thin soil and low fertility barren land. In some places, sweet potatoes are planted year after year, so the soil can not be rotated and fallow, and the soil's water and fertilizer conservation ability is reduced. Soil water and fertilizer conditions can not meet the growth requirements of high-yield sweet potato, which is one of the main reasons for low yield and poor quality of sweet potato.
In the early stage, it is mainly to replenish seedlings in time, intertillage and weed for 2 ~ 3 times before closing the ridge, and cultivate the soil if the ridge surface collapses during the rainstorm. Sweet potato vines will damage stems and leaves, disturb the even distribution of leaves, weaken photosynthetic efficiency, consume nutrients during regeneration of branches and leaves, affect the normal distribution of plant nutrients, and cause yield reduction. When measures such as topdressing and spraying chemicals are taken, vines should be protected to reduce the damage of stems and leaves.
The quality of potato harvest and operation is closely related to potato yield, drying rate, safe storage and processing. Sweet potato tuber is a vegetative body and has no obvious maturity. Generally, the local average temperature drops to 12 ~ 15℃. When the soil humidity is low in sunny days, we should pay close attention to harvesting. Harvest seed potatoes first, and then harvest edible potatoes. Potato pieces should be put into the cellar at any time, and some areas should be cut dry in time. No matter whether it is dug mechanically or manually, it is necessary to minimize leakage; At the same time, it is necessary to avoid potato chips from being broken, otherwise it is easy to be infected with diseases and lead to rot during storage.
Fertilize soil or land
Sweet potato has well-developed root system, creeping growth of stems and vines, and the stem nodes can take root in the soil, which has strong fertilizer absorption ability. Sweet potato mainly absorbs nitrogen, phosphorus and potassium fertilizer, and the demand for potassium is the most, followed by nitrogen and phosphorus.
Nitrogen can promote the growth of sweet potato stems and leaves, expand the photosynthetic area, thereby increasing the photosynthetic capacity and directly increasing the yield of stems and leaves. Early application of nitrogen fertilizer can promote the early growth and development of sweet potato, with multiple branches, fast growth of stems and leaves and early closure of ridges, which lays a good foundation for high yield. Insufficient supply of nitrogen fertilizer, slow growth of stems and leaves, small leaf area, pale color, poor plant growth, and ultimately affect the yield. However, too much or too late application of nitrogen fertilizer will easily lead to excessive growth of stems and leaves and poor potato yield, which will affect the yield.
Phosphorus can accelerate the synthesis and operation of nutrients in sweet potato and improve the quality of sweet potato chips. Phosphorus-deficient stems have small thin leaves, which are dark green and dull. Old leaves appear yellow spots and fall off after turning purple.
Potassium can promote the cambium activity of sweet potato roots and make the tuberous roots expand continuously. In the middle and late growth stage, potassium fertilizer can improve the synthesis and transportation ability of sweet potato carbohydrates, and promote the root swelling, weight gain and quality improvement. Potassium deficiency in the early growth stage, short internodes, small leaves and no leaf extension; Potassium deficiency in the middle and late growth stage, slow growth of stems and leaves and serious yellowing of leaves.
According to research, sweet potato has a long growth period and needs more nutrition. The target yield per mu is 3 tons of fresh potatoes, and pure nitrogen (N) is about 15 kg, phosphorus pentoxide (P2O5) is about 12 kg, and potassium oxide (K2O) is about 24 kg. The general principle of fertilization is to balance fertilization, pay equal attention to promotion and control, promote seedling prosperity in the early stage of fertilization, control seedling length in the middle stage, and protect tail to prevent premature aging in the later stage. The specific fertilization principles are organic fertilizer, chemical fertilizer, base fertilizer, topdressing and early and late stages. Generally speaking, due to the variety of sweet potato in sandy loam or thin land, it is necessary to pay attention to early and heavy application, more organic fertilizer and plant ash, and adequate base fertilizer, early seedling fertilizer and reasonable close planting, closing ridges in advance to enhance coverage, reduce water evaporation and increase soil water content, thus improving sweet potato yield. Recommended fertilization method:
In the north, farmyard manure is generally applied as the base fertilizer, and nitrogen-containing chemical fertilizer is appropriately applied, so that nitrogen metabolism is dominant in the early stage of growth and carbon metabolism is dominant in the later stage. It is advisable to apply potassium dihydrogen phosphate at points or spray it in the middle and late stage in the phosphorus-deficient areas of Huanghuai River Basin. It is hot and rainy in southern potato areas, and it is emphasized to apply topdressing for many times, such as topdressing seedling fertilizer after sowing, topdressing potato fertilizer at the stage of branching and fruiting, topdressing potato fertilizer at the flowering stage of stems and leaves, and topdressing extra-root fertilizer at the later stage.
1), seedling fertilizer:
When ploughing or ridging, apply 1~3 tons of organic fertilizer such as burning soil per mu, and apply 20~30 kilograms of phosphate fertilizer per mu. Before transplanting potato seedlings, urea and compound fertilizer can be applied to the ridge center, and then the soil is covered. Potato seedlings can be inserted or put, and then the soil is covered, which is labor-saving. Potato seedlings can not contact fertilizer to prevent seedling injury, and can absorb fertilizer nutrition as soon as possible at seedling stage, and grow early and quickly. If no fertilizer is applied during ploughing and seedling transplanting, seedling fertilizer can also be applied as early as 7~ 15 days after sowing, when seedlings and leaves turn green and erect. Generally, human excrement and urine can be sprayed appropriately, or urea and compound fertilizer can be applied. Generally, urea10kg per mu and compound fertilizer 20kg (15: 15: 65438).
2), potato strong fertilizer
1 After planting, apply strong potato fertilizer. Generally, urea15 ~ 20kg and potassium chloride 20 ~ 30kg are applied per mu, and furrowing and fertilizing can be done. If conditions permit, plant ash or burning soil on the ridge surface can be properly removed.
3) Tail fertilizer
After three months of planting, strong tail fertilizer should be applied according to the growth situation, and late-maturing varieties or sweet potatoes with poor growth in the later stage should be considered, which are generally not applied.
Irrigation, weeding, loosening soil, raising soil and turning vines.
The advantages of irrigation, weeding, loosening soil and ridging soil are: sufficient water and ventilation are beneficial to high yield and high quality of sweet potato, and can prevent and control pests and diseases. When the weather is dry and the evaporation is large, irrigation is mainly judged according to the dry cracking of the ridge surface, and water is usually poured once every half month. Irrigation should run through the whole ridge. Generally, when the water is over half of the ridge, it is necessary to observe whether the water can gradually wet to the top of the ridge, and to observe whether the ridge is soaked when spraying water.
After irrigation, the border is slightly dry, which means weeding, loosening soil and ridging. The cracks on the ridge surface should be covered with loosening soil to prevent underground pests, such as weevils and stem borers, from getting into the border and eating root tubers and vine heads, which will affect the yield and quality. No matter after irrigation or during the whole growth period of sweet potato without drought irrigation, you can cover the border seam with border mud at any time to prevent and control pests and diseases.
Before and after planting, water properly to keep alive and promote growth. Before closing the ridge at seedling stage, combine with fertilization, loosen the soil 1~2 times, cut off the surface capillaries, and reduce the surface evaporation. When the stems and leaves of sweet potato basically cover the ridge surface, don't pull the vines, so as not to disturb the normal distribution of the stems and leaves and damage the roots, affecting photosynthesis and nutrient absorption. The adventitious roots of sweet potato vines can be used to absorb water and fight drought.
At present, the breeding target of new sweet potato varieties is mostly improved varieties with short vines and few roots, and it is generally not recommended to turn over vines. However, after continuous heavy rain or rainy days, the stems and vines of sweet potatoes will grow white and grow new roots, which will increase the loss of nutrients. It is difficult for new roots in the middle and late stages to bear potatoes. Even if they grow into potatoes, they should be properly controlled to prevent the stems and vines from rooting. Turning over vines should be lifting vines and cutting roots, and gently putting them back in place. The original normal distribution of stems and leaves should not be disturbed, especially when the stems and leaves are inverted, it takes a long time to recover, which seriously affects photosynthesis and yield. The main diseases of sweet potato include sweet potato black spot, sweet potato stem nematode, sweet potato soft rot, sweet potato blast, sweet potato scab, sweet potato tendril blight, sweet potato root knot nematode, sweet potato root rot, sweet potato virus disease and sweet potato purple feather disease. The main pests of sweet potato are weevil, mole cricket, chafer, cutworm, sweet potato moth and so on. The prevention of sweet potato diseases and insect pests should focus on prevention. At present, weevil is the most harmful.
Fungal black spot, nematodiasis and fungal root rot are the main diseases in northern China. Bacterial potato blast and fungal scab are the main diseases in south China. Fungal soft rot is the main disease during storage. Select disease-resistant varieties, prevent metallurgical field diseases, implement crop rotation, establish disease-free seed fields, plant disease-free potato seedlings, and disinfect seed potatoes and seedlings with pesticides. There are many kinds of sweet potato virus diseases, and the symptoms of leaves are purple ring, yellow spot, leaf shrinking, leaf rolling, bright pulse and feather mosaic. Prevention and control methods can include cultivating virus-resistant varieties, eliminating diseased insects in potato fields, using stem tips to detoxify tissues, and cultivating disease-free seedlings. The main pests of sweet potato are sweet potato weevil and sweet potato wheat moth, followed by omnivorous pests such as mole cricket, cutworm and needle worm. In order to control the ant elephant, we should implement the rotation of paddy and upland, and take measures such as raising soil on ridges and cracks in the later stage. Agricultural techniques and pesticides can be used to control other pests.
Weed weevil, also known as sweet potato ant scale or sweet potato weevil, belongs to COLEOPTERA, ant weevil family, and is a destructive pest in sweet potato production in tropical and subtropical regions, which usually reduces the yield of sweet potato by 20-50% or even causes serious losses, and is one of the main limiting factors in sweet potato production. It is distributed in the provinces south of the Yangtze River and has 6-8 generations throughout the year. Adults live longer and generations overlap. From seedling to harvest, weevil larvae and adults can harm sweet potatoes. The larvae mainly eat potato vines and potato pieces, which makes the stems and leaves grow slowly. At the same time, a large number of larvae eat potato pieces, which make them black and smelly and inedible for people and animals. At present, no effective insect-resistant genes have been found in the world, and no varieties with high resistance to weevil have been cultivated so far.
Because weevils mostly damage underground tubers and their generations overlap, it brings great difficulties to artificial and drug control. At present, there is no ideal control method for this pest. The main methods to control underground pests of sweet potato are ecological control and chemical control. General chemical pesticides are expensive to control, and they are rarely used because of problems such as residual poison. In addition, weevils also have recommended sex pheromones, and the control effects vary from place to place. Sex pheromone of weevil is a volatile and non-toxic chemical substance secreted by female weevil, and there is no residual toxicity and drug resistance. They are used to trap and kill males, so that females can't find males to mate and can't reproduce, thus greatly reducing the density of weevils in the field. However, it has also been reported that it is difficult to kill all males, even if a few males are left, it may trigger a new round of weevil harm.
It is suggested that comprehensive measures should be taken to control weevil.
1), paddy-upland rotation
2) Irrigate the fields with many sweet potato diseases and insect pests, kill the insect source, fully plough and harrow the soil, and treat them with soil treatment agents such as "Haoniandong" and "Insecticidal Pill".
3) In order to kill the insect source of the seedlings, pesticides such as dimethoate can be sprayed on the sweet potato fields where the seedlings are to be collected. Before planting, soak the base of sweet potato vine with 500 times dimethoate 1~2 minutes. After planting 1 week, spray dimethoate or trichlorfon (normal dosage) on potato seedlings and vine heads, or use 500 times 80% trichlorfon. All the above control measures need not be used, but should be selected flexibly according to the specific situation, and pesticides such as dimethoate should be used according to the normal drug use instructions.
Other main pests of sweet potato are leaf roller moth, sweet potato moth, Spodoptera litura and so on. Insecticides such as dimethoate, dichlorvos and chlorpyrifos can be used according to the normal medication instructions and sprayed in the afternoon.
Main measures to control sweet potato diseases
1), select disease-resistant varieties, and pay attention to disease quarantine of seed potatoes and seedlings. 2) Cultivate disease-free seedlings, choose disease-free potato seedlings without disease areas, or choose virus-free seedlings.
3) Soak the sweet potato vine with 500 times solution of 50% carbendazim or 50% thiophanate methyl for more than 2 minutes, dry it and plant it.
4) If a diseased plant is found in the field, it should be immediately pulled out and burned, and sprayed with 1000 times of 50% carbendazim. According to the situation, it can be sprayed continuously 1 time every 7 days until it is eradicated.
5) Thoroughly clean up sick and disabled plants during harvesting, pay attention to the rotation of paddy and upland crops, strengthen the management of water and fertilizer, pay attention to drainage, ventilation and air exchange, and appropriately increase the application of plant ash and lime, so as to make plants grow healthily and enhance their disease resistance.