How to manage grafted watermelon seedlings?

(1) Healing period management temperature management. The suitable temperature for grafting seedling healing is 25℃ ~ 26℃ during the day and 20℃ ~ 22℃ at night. Too high or too low temperature is not conducive to joint healing and affects the survival rate. Experiments show that the interface healing time is 2 ~ 3 days at the temperature of 22℃ ~ 25℃, and the survival rate is 95%. 15℃ low temperature lasted 10 hour, delayed 12 days, and the survival rate decreased by 5% ~ 10%. The survival rate decreased by more than 15% if the high temperature above 40℃ lasted for 4 hours and the healing was delayed for 2 days. Therefore, in early spring and low temperature period, measures should be taken to increase temperature and keep warm; The high temperature in summer is within the appropriate range, which can be slightly reduced in the future. Generally, from 8 days to 10 days after grafting, the seedlings will resume normal seedling management after survival. If the grafting method is adopted, the scion should be cut off after the seedlings survive. After root cutting, the temperature should be raised appropriately to promote wound healing, and routine management should be resumed after 2 ~ 3 days.

Humidity management. Before the vascular bundle of rootstock and scion is connected, the water source of scion is cut off, and there is very little water source just because of the water infiltration between rootstock and scion. If the air humidity in the environment is low, the scion is easy to wilt due to strong transpiration, which seriously affects the survival rate of grafting. Therefore, maintaining high air humidity before grafting survival and preventing scion wilting are the key to successful grafting. Generally, the relative humidity of air should be kept above 95% within 1 week after grafting. The measures taken are to water the seedling pots immediately after grafting, move them into a well-watered small arch shed, pay attention to warm water in winter and cold water in summer, and then cover the shed tightly to make the air temperature in the shed close to saturation. The sealing time is 4 to 5 days. The closing time is also related to the grafting method. The sealing time of scion with root can be shorter, and the sealing time of scion with root can be longer. After that, a small amount of ventilation was started in the early morning and evening when the air humidity was high, and then the ventilation volume and ventilation time were increased day by day, but the air humidity was still high, and 1 ~ 2 times were sprayed at noon every day until the seedlings survived completely, and the routine humidity management of seedlings was resumed.

Lighting management. After grafting, in order to avoid scion wilting caused by direct sunlight, proper shading should be carried out after grafting. The shading method is to cover the plastic shed with grass, paper, newspaper, sunshade net and other coverings. Generally, it is shaded all day within 3 ~ 4 days after grafting, and then weak light is transmitted and scattered at the edge of the shed in the morning and evening, and the light transmission time is gradually increased. After 8 days to 10 day, normal lighting management will be resumed. If the butt joint method is adopted, the scion is cut off after survival, and the root is cut off and shaded for 2 ~ 3 days. In case of rainy weather after grafting, there is no need to shade the sun. It is worth noting that shading should not be excessive or too long, otherwise it will affect the survival and normal growth of grafted seedlings. The results showed that the survival rate of grafted seedlings was the highest under the conditions of 5000 le light and long sunshine12 h. Weak light and long sunshine time are beneficial to the survival and robust growth of grafted seedlings. If the shading is excessive and the time is too long, the grafted seedlings will not get sunshine for a long time. Photosynthesis is blocked, nutrition is exhausted and death occurs. Therefore, the grafted seedlings should be protected from sunlight for 3 ~ 4 days at the initial stage of grafting, and then gradually increase the light transmission amount and time, and give the grafted seedlings normal lighting conditions in time after survival.

(2) Managing root cutting after survival. Grafting method is adopted. After the grafted seedlings survive, it is necessary to cut off the scions in time to make them grow completely on the rootstock. Generally, the rooting time is from 10 to 12 days after grafting. The method is to cut off or cut off the hypocotyl of the scion with a blade or small scissors below the joint 1 cm, and then cut another knife at 0.5 cm to leave a gap for the hypocotyl to avoid self-healing. You can also remove the root of the scion after cutting. After root cutting, temperature, humidity and shading should be appropriately increased to promote wound healing. Control scion withering.

Hierarchical management. Watermelon grafted seedlings generally heal completely in about 7 days under suitable temperature, humidity and light conditions, and the grafted seedlings survive and begin to grow. However, due to the inconsistency of rootstock thickness, size and scion size during grafting, the quality of surviving seedlings will be different, so it is necessary to carry out hierarchical management. Put the big seedlings with firm healing and rapid growth recovery together; Seedlings with poor interface healing and slow growth should be placed in places with good temperature and light conditions to create good conditions for them to catch up with big seedlings gradually, while seedlings with poor interface healing and difficult to return to normal growth can be eliminated.

Remove the buds. Because the growth point of rootstock is cut off during grafting, it will promote the germination of rootstock axillary buds, especially after a period of high temperature, high humidity and shading management, axillary buds grow rapidly. If they are not removed in time, new leaves will soon grow, which will affect the growth and development of scions. After the grafted seedlings survive, the buds of sleepers should be removed in time and cleaned thoroughly. If there are buds in the future, you should pull them out at any time.

Remove the fixture. Most grafting methods need to fix the interface with fixtures, and after the grafted seedlings survive, the interface fixtures should be removed. However, it was released too early. First, grafted seedlings, especially those grafted by docking method, broke at the interface due to movement. If it is released too late, the presence of fixative will affect the growth and development of rhizome.

Therefore, the fixture should be removed in time according to the specific situation. Splitting usually removes fixtures after one week of survival, and docking can be postponed appropriately, even after planting, but it should not affect the growth of seedlings, otherwise it should be removed as soon as possible.

Exercise at low temperature. The management of light, temperature and water after the survival of grafted seedlings is the same as that of conventional seedling raising. From 7 days to 10 days before planting, low-temperature exercise should be carried out, ventilation should be gradually increased, and the temperature of seedlings should be reduced, so as to improve the stress resistance of grafted seedlings and make them easy to survive after planting.