Solutions for High-Temperature Disorders in Greenhouse Cucumbers
Sowing and Seedling Raising 1. Variety Selection: Choose varieties that are not prone to bolting and are relatively cold-resistant. 2. Pre-germination Sowing ①Determining sowing time: For cultivation in large, medium and small tunnels, use protected seedling raising from early January to mid-February; for open-field cultivation, direct sow from late February to April. ②Pre-germination sowing: After soaking seeds in warm water, germinate at 15°C-20°C and sow; select...
For cucumbers grown in greenhouses, after April arrives, as temperatures gradually rise, if ventilation is not timely or is inadequate, the temperature inside the greenhouse can sometimes reach as high as 40-50°C, and sometimes in the afternoon can exceed 50°C, causing damage to cucumber growth and development. In mild cases, the small leaves of the plant wilt and stop growing; in severe cases, the leaves of the entire plant wilt, greatly affecting cucumber yield and quality. When seedlings encounter high temperatures, they show excessive vegetative growth, with small, drooping cotyledons, and sometimes flower topping occurs. When young plants encounter high temperatures, leaf color is pale, leaves are large and thin, not spread out, and internodes elongate or plants become leggy. When mature plants are affected, 1-2 mm near-circular to elliptical chlorotic spots first appear on the leaves, then gradually expand. After 3-4 days, the mesophyll and veins of the entire plant's leaves turn yellow-green from top to bottom, with the upper part of the plant being most severely affected. In severe cases, the plant stops growing. When the greenhouse temperature reaches 48°C, within a short time it causes the small leaves near the growing point of the cucumber to wilt and the leaf margins to turn black. If the duration is longer, the entire plant's leaves wilt, appearing as if scalded by hot water. For control, strengthen ventilation and air exchange. Cucumbers have suitable temperatures at each stage. During seedling raising, the bed temperature should be maintained at 25-30°C during the day and 16-18°C at night. After 80% of seedlings emerge, the temperature must be lowered promptly to 20-25°C during the day and 14-16°C at night. After transplanting, during the seedling recovery period, the daytime temperature should reach 30-35°C, and at night not lower than 18-16°C. After seedling recovery, bring the room temperature to about 30°C during the day and 16-14°C at night. During the fruiting period, maintain the greenhouse temperature at 28-30°C during the day and 16-18°C at night, with relative humidity below 85%. During production, always check the thermometer to monitor temperature changes. When the temperature is slightly high, ventilate and cool through the greenhouse doors and vents. If the temperature still remains high, then uncover the bottom edge on the south side to bring the greenhouse temperature down. At the same time, pay attention to watering, preferably between 8-10 AM. Do not water at night or on cloudy days. Also note that the temperature difference between the water and the soil should be below 5°C. The suitable relative humidity for cucumber growth is about 85%. When greenhouse relative humidity is above 85%, ventilate to reduce humidity. When the evening temperature is 18-20°C, ventilate for 1 hour to reduce nighttime humidity, prevent "leggy growth," and avoid high-temperature disorders. Because higher temperatures cause leggy growth, in production you can promote fruit setting to inhibit leggy growth, so as to avoid excessive vegetative growth. For this purpose, you can use Baoguoling hormone 100-fold solution to spray or dip flowers, which can promote early maturity and increase yield while also preventing leggy growth. Appropriately increase the application of phosphorus and potassium fertilizers. You can also spray multi-element compound organic active liquid fertilizer or 0.2% potassium dihydrogen phosphate solution or 0.1% urea solution as foliar topdressing 2-3 times, which can effectively improve the plant's heat resistance. In cases of sustained high temperatures or atmospheric drought, greenhouse cucumbers have high evaporation and vigorous respiration, consuming a lot of water. If this lasts a long time, wilting and other phenomena will appear. At this time, appropriately increase the frequency of watering. Water thoroughly each time, then water again after two days, so the seedlings can fully absorb enough water. How to correct abnormal growth in protected cultivation cucumbers? 1. Internodes and petioles too long. This is mainly leggy growth caused by high temperature and high humidity. Appropriately control water and fertilizer, increase ventilation, reduce humidity and lower temperature. 2. Leaf wilting. During the fruit enlargement period, lower leaves wilt; generally the older the leaf, the earlier it wilts. This is mainly caused by insufficient water. During the full fruiting period, sufficient water supply must be maintained, and appropriate intertillage and soil loosening should be carried out. 3. Plants short and small, leaves yellow-green, leaves small and thin, lower leaves aging, early leaf drop. This is mainly caused by insufficient nitrogen, reduced chlorophyll content, and insufficient photosynthetic products. Corrective measures: On the basis of applying sufficient base fertilizer, immediately carry out topdressing. And according to the principle of small amounts and multiple applications, appropriately increase the amount and frequency of topdressing. 4. Leaf color dark green, leaves thickened. This is mainly caused by nighttime, especially after sunset, temperatures being too low, so the photosynthetic products produced during the day cannot be transported out in time and accumulate in the leaves. Corrective measures: Increase room temperature and strengthen nighttime insulation measures. 5. Plants dwarfed, internodes short, especially obvious near the top, young leaves small, leaves curling upward. In severe cases, these leaves dry up from the edges inward. Main cause: due to soil acidity being too high (pH<≤5.5），土壤中缺乏钙素。室温高，土壤干燥，或土壤溶液中总盐浓度过高等使植株缺钙或钙的吸收受阻引起的。矫正措施：针对病因有针对性地采取改良土壤，加强温度和水分管理，叶面喷施钙剂等。 6.卷须呈弧状下垂，特别是连阴天放晴后。原因是水分不足，如果是连阴天，则由于根系吸收的能力较弱，放晴后，水分吸收跟不上光合作用及蒸腾的速度，造成的生理干旱。矫正措施：立即加强水分管理。如果连阴天放晴后，需进行叶面喷水进行补救。 7.卷须直立。主要是水分过多。矫正措施：在保温基础上，及时放风，加强中耕减少土壤湿度。 8.卷须细而短或先端卷起。主要是植株营养不良或已经老化。矫正措施：加强肥水管理，特别是盛果期一定要供给充分的肥水，也可以疏去一部分弱花或弱果，防止造成结果不良，影响产量。 9.雌花淡黄，短小，弯曲，横向开放，甚至向上开放。主要是缺乏钾，使光合作用产物向花的运输受阻。或土温过低及板结等原因使根部功能降低，导致生长势衰弱引起的。矫正措施：及时加强钾肥管理，相应改善土壤温度、湿度，进行中耕松土，加强土壤通透性。 10.开花到顶。即开花部位距生长点很近。主要原因：水肥条件较差或定植过龄的老苗、僵苗，是营养生长过弱的标志。矫正措施：加强水肥管理，特别是氮和磷的充足供给，促进营养生长，扩大叶面积，必要时，可适当除去部分雌花，减少部分植株负担。 11.在盛瓜期，花器发育不良，子房变小，有的在开花前凋萎，有的在开花后脱落，造成结果不良。主要原因：土壤含水量偏低，或氮、磷、钾的供应不足，导致植株营养生长受阻引起的。矫正措施：在盛瓜期要注意加强肥水管理，特别是要平衡施肥。