(1) According to the position where the secondary growth of garlic plants occurs, the secondary growth types of garlic can be divided into the following three types:
① Secondary growth of outer layer type. There are 1 to several scaly buds sprouting on the axils of the outer leaves of garlic plants. The scale buds delay entering dormancy and continue to differentiate and grow, forming single garlic, or split garlic without flower buds, or split garlic with flower buds. In this way, some garlic cloves or small garlic heads are planted on the periphery of garlic, which makes the whole garlic deformed. This secondary growth has the greatest impact on the quality of goods.
② Secondary growth of inner layer type. In the axils of the inner leaves of garlic plants, the normally differentiated scale buds delay to enter dormancy, and the protective leaves around the scale buds continue to grow, protruding out of the plant leaf sheath and forming multiple branches. Some branches develop into normal garlic cloves; Some branches developed into garlic cloves, and a few also formed flower buds. The slight secondary growth of the inner layer has little effect on the shape of garlic. In severe cases, the garlic bolt becomes shorter, the weight of the garlic bolt decreases, the garlic cloves are loosely arranged, and the upper part of the garlic bolt is easy to crack. The shaped garlic clove looks like a normal garlic clove and is usually chosen as garlic seed. However, after sowing, more than two garlic seedlings will grow from one seed flap, which affects the yield and quality of garlic seedlings.
③ Secondary growth of balloon type. The aerial bulb in the involucre of young garlic shoots delayed into dormancy, continued to grow into small plants and even sprouted young garlic shoots. Plants with secondary growth of bulbs on the ground often shorten garlic shoots and lose commercial value, but have little effect on garlic. The incidence of this type is generally low.
In addition to the above three basic secondary growth types, sometimes the two types will be mixed on the same plant. (2) Reasons for the secondary growth of garlic ① Variety inheritance. Some varieties only have secondary growth in the inner layer, but no secondary growth in the outer layer, such as Tianjin Red Peel, Shanghai Jiading Garlic, Xinjiang Yining Red Peel, Xinjiang Jimsar White Peel, Qinghai Golmud Red Peel, Ledu Garlic, Liaoning Kaiyuan Dog Garlic, Jiangsu Taicang White Garlic, Yinchuan Purple Peel, Heilongjiang Acheng White Peel and Acheng Purple Peel. Some varieties such as Ershui Jujube, Pengxian Garlic, caijiapo Red Peel, Cangshan Garlic, Putuo Garlic, Bijie Garlic and Shanxi Purple Peel can grow for the second time. However, some varieties basically grow twice, such as Guangdong Xinhui Huo garlic, Guangdong Jinshan Huo garlic, Guangdong Puning garlic and Guangdong Shaoguan Zhongxin garlic.
Although the secondary growth type of garlic mainly depends on the heredity of varieties, the genetic stability of different varieties is different. Generally, only varieties with secondary growth in the inner layer and varieties without secondary growth have stable heritability, and their genetic characteristics can be maintained in different years under field cultivation conditions. However, the inheritance of varieties with both inner and outer secondary growth is not stable enough, sometimes both of them occur at the same time, and sometimes only the outer secondary growth or only the inner secondary growth occurs.
② Temperature and humidity of garlic seeds during storage. The temperature of garlic seeds during storage has a significant effect on the secondary growth. Low temperature can promote the secondary growth, but different varieties have different responses to low temperature. Caijiapo red-skinned garlic is most sensitive to low temperature (0 ~ 5℃) and cold conditions (14 ~ 16℃), and the secondary growth of the outer layer and the inner layer increases greatly, especially the secondary growth of the inner layer. The response of Cangshan garlic to low temperature chilling injury was the second, and the secondary growth of outer layer and inner layer also increased greatly, among which the secondary growth of outer layer increased greatly.
Garlic in autumn sowing areas is mostly stored at room temperature after harvest, and it will not encounter low temperature and cold conditions that are easy to induce secondary growth during storage. However, after autumn sowing, from seedling stage to flower bud and scale bud differentiation and development stage, garlic seeds will encounter low temperature and cold, so even without low temperature and cold treatment, there is the possibility of secondary growth, but the severity is lighter than that of low temperature and cold treatment.
Garlic in spring sowing areas should be stored until sowing in March-April of the following year. In order to prevent garlic from freezing, the lowest temperature in the storage place should be controlled at about 0℃. During the storage period of 7-8 months and a period of time after sowing in the open field in early spring, there are low temperature and cold conditions to induce secondary growth.
Besides temperature, air relative humidity also affects the secondary growth of garlic seed storage sites, and there is interaction between temperature and air relative humidity. Cheng Zhihui et al. (1992) reported that garlic seeds were stored at 5℃ and 75% ~ 100% air relative humidity 30 days before sowing, and the secondary growth index of the outer layer in the second year after autumn sowing was 3.3 times higher than that stored at 5℃ and 25% ~ 50% air relative humidity. The secondary growth index of inner layer type increased by 65438 0.9 times. However, garlic seeds stored at 15℃ and 25℃ have no significant difference in the secondary growth degree of the outer layer or the inner layer under different air relative humidity (25% ~ 100%). Therefore, in order to reduce the occurrence of secondary growth, garlic seeds should not only avoid low temperature during storage, but also avoid air relative humidity above 75%.
③ sowing date. In the domestic reports on the secondary growth of garlic, it is considered that early sowing date is one of the important reasons for the secondary growth. According to years of investigation and study, it is found that the relationship between sowing date and secondary growth varies with varieties, dormancy degree of garlic seeds, storage environment of garlic seeds, emergence speed after sowing and soil moisture, and the influence of sowing date on different secondary growth types of the same variety is also different.
Varieties with secondary growth in both outer and inner layers, such as caijiapo red-skinned garlic in Guanzhong area of Shaanxi Province, were sown earlier than the normal sowing date (mid-to-late September) and emerged quickly after sowing. When the seedlings grow vigorously, the secondary growth of the outer layer is serious. If the sowing date is early, but the garlic seeds are still dormant, the seedlings do not emerge after sowing and the growth is weak, then early sowing will not cause the secondary growth of the outer layer. Varieties prone to secondary growth of inner layer, such as Cangshan garlic, have no significant effect on secondary growth of outer layer in Guanzhong area of Shaanxi Province, but before 5438+ 10 in mid-June, the secondary growth of inner layer is more likely to occur later than early sowing. If garlic seeds are cooled and sown early, the secondary growth of outer and inner layers will be promoted.
The effect of sowing date on secondary growth is also related to soil moisture. 199 1 The results of two-factor experiment with Cangshan garlic showed that sowing date and soil moisture had little effect on the secondary growth of the outer layer, but had effect on the secondary growth of the inner layer. No matter whether the sowing date is early or late, when the soil moisture is high (the relative soil moisture is 90%), the secondary growth rate of the inner layer type is significantly higher than that when the soil moisture is low (the relative soil moisture is 50%). High soil moisture and early sowing date are more conducive to the secondary growth of inner layer type; Although the sowing date is early, when the soil moisture is low, it is not conducive to the secondary growth of the inner layer.
④ The size of garlic cloves. When garlic seeds are stored at room temperature, garlic cloves (weighing 3-4g) are more prone to secondary growth in the outer layer than garlic cloves (weighing 1-2g), but the size of garlic cloves has no significant effect on secondary growth in the inner layer. Cold treatment (temperature 16 ~ 17℃, air relative humidity 95%) was carried out 25 ~ 30 days before sowing. The bigger the garlic clove, the more serious the secondary growth of the outer layer. However, small garlic cloves are generally easier to grow in the inner layer than garlic cloves.
⑤ Irrigation. Irrigation period and irrigation amount have important effects on the secondary growth of garlic. During the whole growth period, especially after the differentiation of scales and buds, irrigation is frequent, the amount of irrigation is large each time, and the soil moisture is high (the relative water content is 80% ~ 95%), which can promote the secondary growth of the outer layer and the inner layer, but the former has greater promotion effect than the latter. When the soil moisture is low (relative moisture content is 50%), the secondary growth of the outer layer and the inner layer does not occur, but the yield of garlic bolts and garlic heads decreases.
⑥ Fertilize. On the basis of applying organic fertilizer as base fertilizer, the amount and times of nitrogen fertilizer also have an impact on secondary growth. When the amount of nitrogen fertilizer is large, the rate of secondary growth plants increases. The occurrence of secondary growth is different with the same amount of nitrogen fertilizer and different times of nitrogen application. According to the experiment, 30 kilograms of urea was applied every 667 meters, and 65,438+0/3 was applied to the treatment area at sowing date, rotten mother stage and turning green stage respectively. The secondary growth of outer layer type and inner layer type is carried out twice at sowing date and seed setting period, or at sowing date. Farmers in garlic producing areas in Shaanxi believe that the more available nitrogen fertilizer is applied after garlic turns green in early spring, the more serious the secondary growth is.
⑦ Covering cultivation. There are two ways of garlic mulching cultivation, one is plastic film mulching cultivation, and the other is plastic arch shed mulching cultivation. At present, the former is widely used. Production practice has proved that plastic film mulching cultivation of garlic can increase production and income, but sometimes there are phenomena such as secondary growth, irregular garlic shape, enlarged garlic petals, shortened garlic bolts and abnormal development, which are related to the changes of soil temperature, humidity and nutrients after plastic film mulching. During plastic film mulching cultivation in arch shed, both the covering time and the uncovering time have effects on the secondary growth. In autumn sowing garlic, the film mulching time is early, the film uncovering time is late, and the secondary growth increases. (3) Measures to prevent the secondary growth of garlic Garlic producing areas, especially the export base of commercial garlic, should know the secondary growth types of local main varieties. When introduced from other places, it is best to carry out variety tests with the main purpose of preventing secondary growth, especially the secondary growth of the outer layer. In autumn sowing areas, garlic seeds can be treated in tunnels (16 ~ 17℃) or refrigerators (0 ~ 5℃) for about 30 days before sowing, and the seeds can be sown early. By investigating and counting the ratio and index of different types of secondary growth plants at harvest, varieties that are insensitive to the conditions of inducing secondary growth can be screened accurately and quickly. Of course, the choice of garlic varieties should also consider the production purpose and other economic characteristics.
Garlic seed storage places should keep the temperature above 20℃ and the air relative humidity below 75%. Garlic seeds should be hung and stored in a well-ventilated room in autumn sowing areas, and the problem of long low temperature period during storage of garlic seeds in spring sowing areas should be solved. When the main purpose is to produce commercial garlic, don't blindly sow it early. In particular, garlic seeds should not be cooled or treated at low temperature in order to promote rapid emergence after sowing. According to the characteristics of secondary growth of different garlic varieties, the suitable sowing date range should be determined through field experiments in different years. Varieties prone to secondary growth of outer layer type, such as caijiapo red-skinned garlic, should be sown late in time; Varieties prone to internal stratification, such as Cangshan garlic, should be sown early in an appropriate period.
According to the secondary growth characteristics of different varieties and different production purposes, garlic cloves with appropriate size were selected for sowing and appropriate planting density was adopted. For example, when Cangshan garlic is planted with garlic cloves (weighing more than 5g) for the main purpose of producing commercial garlic, it should be densely planted with a row spacing of 22cm and a plant spacing of 10cm. When garlic cloves are planted thinly, it can promote the secondary growth of the inner layer. When the main purpose is to produce garlic bolts, the row spacing is 22 cm and the spacing between plants is 7 cm, which can not only improve the yield of garlic bolts, but also reduce the occurrence of secondary growth of inner layer type.
The base fertilizer is organic fertilizer and NPK compound fertilizer. When using quick-acting nitrogen fertilizer as topdressing, it is forbidden to apply it in large quantities for many times, especially in the turning green period, and it is necessary to apply less or no quick-acting nitrogen fertilizer. During the whole growth period, especially during the differentiation of flower buds and scale buds, do not irrigate heavily for many times. Of course, the water and fertilizer management of garlic, like other technical measures, should give consideration to high yield and high quality and minimize secondary growth; Achieve high yield and high quality.
When garlic is planted under plastic film, the following points should be paid attention to:
First, the sowing date of garlic in autumn is delayed by 5 ~ 10 days compared with that of non-mulching cultivation, which makes the seedling growth less vigorous. After differentiation, the flower buds and scale buds are in an environment where the temperature continues to rise and the sunshine time is gradually lengthened, which is beneficial to the normal development of flower buds and scale buds. The sowing date of spring sowing garlic should be earlier than that of uncovered cultivation, so that the growth stage can be advanced, and the differentiated flower buds and scale buds can have sufficient growth time before the arrival of high temperature and long sunshine, and then bolting and bulb formation can be smoothly carried out under high temperature and long sunshine.
Second, apply long-acting organic fertilizer and chemical fertilizer as base fertilizer, and apply it once in the border. Compared with non-mulching cultivation, the amount of nitrogen fertilizer decreased by about 1/3. The dosage of phosphorus and potassium fertilizer is the same as that of open field cultivation. Don't topdress before uncovering the film.
Thirdly, during the plastic film mulching cultivation in the arch shed, the mulching time should not be too early, whether in autumn or spring, so that the seedling stage can withstand enough low temperature and promote the differentiation of flower buds and scales. It is best to cover the film after the flower buds and scale buds begin to differentiate, so as to increase the temperature in the greenhouse. At the same time, the sunshine time is gradually lengthened, and flower buds and scale buds can develop normally. It should not be too late to uncover the plastic film. Under normal circumstances, when the temperature is stable above 15℃ and the young garlic shoots are about to show their involucre, the plastic film can be removed. The secondary growth increased when the film was uncovered late, and the air temperature and ground temperature were too high when the flower stems grew rapidly, which was not conducive to the development of flower stems and increased the number of abnormal flower stems.
Fourth, when working in the field, avoid mechanical damage to the underground or aboveground parts of plants.