Symptoms Corn is native to the tropics and is a warm crop with high temperature requirements. In some years, due to the low temperature, corn is often chilled. Seedling emergence to low temperature, emergence of delayed seedlings, weak seedlings, thin, seed germination rate, decreased germination and other phenomena, and has an obstructive effect on the growth of plant functional leaves. At the four-leaf stage, the plants are obviously short and short, the growth of the plants is delayed, the photosynthesis intensity and the effective leaf area of ​​the plant functional leaves are significantly reduced; from the fourth leaf stage to the silking stage, the low temperature duration is long, the plant height, stem, leaf area and The weight of dry matter per plant was affected; from silking to maturity, the effective accumulated temperature was not sufficient due to low temperatures. During the grain filling stage, the low temperature slowed down the rate of dry matter accumulation in the plants and the speed of grain filling decreased, resulting in reduced yields. Etiology From the point of view of the whole growth period of corn, buds, seedlings, and filling stages are very sensitive to low temperatures. Low temperature at seedling stage reduces photosynthesis intensity and affects plant growth. Even after temperature recovery, there is still a certain low-temperature aftereffect, and then gradually recover. At the same time, the growth of functional leaves of plants was inhibited at low temperature, which affected the total effective leaf area of ​​the plants, resulting in decreased photosynthetic productivity. An effective accumulated temperature of 79.4 days was required from sowing to emergence, and the biological lower limit was 9.3°C. The number of days from sowing to emergence increased with increasing temperature. The average temperature is 15°C and it takes 15-20 days. The average temperature is 12;8—16.8°C and the output is high. Above or below this temperature will reduce production. At an average temperature of less than 10°C, the photosynthetic productivity decreased significantly. The average temperature of seeds sown and raised in production rises or falls by 1°C, and the output per 667m2 increases or decreases by 10.6kg. From the emergence to the silking stage, it enters the vigorous stage of corn growth. Especially after the jointing stage, the temperature rises and grows quickly, which is beneficial to the increase of plant height, stem diameter, leaf area and unit weight. If the average temperature is lower than 23.9°C, it will be affected. If it is lower than 23°C, it will reduce production. Spinning to maturity is an important period of yield formation, and still requires a higher temperature. From the beginning of silk spinning to 13 days after silk spinning, it was a period of slow weight gain. From 14 to 45 days after silking, it was a period of rapid weight gain, and the filling speed increased linearly. After 46 days, it turned mature and turned to the stage of slow weight gain. During this period, if the average temperature rises or falls by 1°C, the production capacity of 667m2 can increase or decrease by 76.6kg. It seems that the temperature changes during silking to maturity, especially when the temperature is low, has a greater impact on the yield than the time from sowing to emergence. 2L-size Carrot,2L-size Fresh Carrot,Fresh Carrot Size 2L,2L-size Red Color Carrot Yirun Agricultural Cooperative , https://www.yiruncn.com
Control methods (1) There is a great difference in the tolerance to low temperature among maize varieties. Therefore, it is necessary to select local varieties that are suitable for low temperature, high yield, and high quality for local conditions. (2) Strictly determine the sowing date according to the climate zone scientifically, and sow early sowing so that the temperature indicators of each growth stage can be met. If sowing to the emergence of the best temperature is 12.8—16.8 °C, not lower than 10 °C; emergence to the average temperature of silking is higher than 24 °C is appropriate, not lower than 23 °C; spinning to maturity requires higher temperatures In order to benefit from photosynthesis, especially during the late period of high temperature, the temperature difference between day and night is beneficial to dry matter accumulation; the grain formation to the filling period is in July, the temperature is higher than 23°C, and the accumulated temperature is about 300°C, which can generally satisfy. 13-45 days after spinning, it enters a rapid growth stage. The accumulated temperature is 1000°C, and the temperature of 20°C can be successfully completed. Late planting (usually sowed after June), into the rapid growth phase of the grain average temperature is lower than 20 °C or lower, the accumulated temperature is only 910 °C, can not meet the grout maturation needs, so that the impact of low temperature on the yield is relatively large, so we must determine Suitable for the local sowing to meet the temperature needs of the post-maize sowing period 1 to achieve early sowing. (3) The application of phosphate fertilizer at seedling stage can improve the growth environment of corn, and it has a certain effect on the reduction of cold damage. It is also possible to use 50ml of glutinous liquid fertilizer and seed dressing of 500m of water to increase cold resistance. Can also be used biological potassium fertilizer 500g 250m1 seed dressing, after sowing a little dry, enhance resilience. (4) If necessary, use seedling transplanting. (5) Promote the adoption of corn cover film cultivation method Common forms: 1 corn flat wide film. 9 corn ridges are covered with narrow sections. 2 Takada interplanting a film for two purposes. 4 square nest sowing film. 5 埯åç”° or æ’®ç§è†œè†œã€‚ 6 furrows covered with rain. 7 high yield pit film. 8 membrane side corn. 9 arch shed plus two layers of plastic film. 10 Corn seedlings transplanted. Using corn mulching cultivation, the field management process is basically the same as the field cultivation techniques, but slightly different from the sowing to the uncovering stage. The key is to master the two key technologies of laying and uncovering the film to ensure that the seedlings are fully grown and the seedlings are strong. Technical points: First, the fine soil preparation. The north should prepare, fertilize, honing and repressing in the autumn, and in the early spring, it should be ridged and ridged. If there are irrigation conditions, the bottom of the river should be filled with water in the autumn and winter, and the water should be repressed and smashed at a proper time to prevent the loss of water. The second is to use good breeds. After corn is covered with plastic film, it strives for an effective accumulated temperature of 250-300°C and prolongs the birth season. Therefore, it is possible to choose a species that is 10 days longer than the growth period of local corn. The third is reasonable close planting. It is required to be suitable for density, with less membranes and convenient management. Wide and narrow row or large and small ridge planting methods can be used, that is, a large row spacing of 80cm, a small row spacing of 25cm, a 70-75cm wide film covering two rows of corn, and both sides pressed into the film l0cm. The advantage is that the density can guarantee 3,800 to 4,500 strains, with good ventilation and light transmission, and it can exert its edge advantage. Use 0.5kg per 667m2 membrane. In general, the density can be increased by about 10% to 15% compared with open corn. The fourth is early sowing and filming. Generally 10-15 days earlier than the open field, after sowing first on both sides of the ridge to open a ditch, ditch exploration 5cm, the plastic film close to the ground, elastic fit, film pressure soil compaction, the film's lighting surface above 35cm. Serious grass damage, sowing after the use of cable 100g or Simazine 150g, the water on the ridge surface spray, spray and then covered. The fifth is to promote mechanical coating. Sixth, the film was released. After sowing the corn covered with film, timely removal of film and seedlings is crucial. The film-covered corn emerged 10-15 days after the first leaves of the seedlings began to rupture and lay the seedlings in a timely manner, and the seedlings were put too late, and it was easy to suppress the corn plants or burn the leaves when sealing the holes. Breaking the membrane is the best choice for sunny afternoons, so that seedlings get exercise. When laying seedlings, use a knife or bamboo to break the 12cm hole, release the seedlings, and then use fine wet soil to seal the gap along the stem base of the seedlings to prevent entering the cold air and maintain the temperature and humidity inside the membrane. After the average daily temperature rises above 25°C, the plastic film should be removed to facilitate management. The use of photodegradable films and biodegradable films is advocated. (16) Advocate the application of "Farmer Po" No. 1 30m1 mixed corn seeds, so that the developed roots can improve disease resistance and germinate early for 36 hours. In the period of large corn trumpet, "Farmer's Pod" 90ml, 50kg of water spray, can close the stomata of the leaves, reduce water transpiration, improve drought resistance.