The index of heat damage in maize is based on moderate heat damage, 36Â°C at seedling stage, 32Â°C at reproductive stage, and 28Â°C at maturity. Temperatures above 32 Â°C during flowering are not conducive to pollination.
Taking the average temperature during the whole growth period as the standard, the mild heat damage is 29 Â°C, the production is reduced by 11.9%; the moderate heat damage is 33 Â°C, the production is reduced by 52.9%; the severe heat damage is 36 Â°C, which will result in the production. The highest temperature of 38-39 Â°C causes high temperature heat damage. The longer the time, the more severe the damage and the more difficult it is to recover.
The main influence of high temperature on corn growth
1. Impact on photosynthesis
Under high temperature conditions, the activity of photosynthetic protease is reduced, the structure of chloroplast is destroyed, the pores are closed, and photosynthesis is weakened. On the other hand, under high temperature conditions, respiration is enhanced, consumption is increased, and dry matter accumulation is decreased. The longer the high temperature stress at 38-39 Â° C, the more serious the plant is, the harder it is to recover and the longer it takes.
2, shorten the growth period
High temperature forces various physiological and biochemical reactions in the process of corn growth to accelerate, and each growth stage is shortened. For example, when the differentiation time of the ear is shortened, the number of florets in the ear is reduced, and the ear is smaller. In the late growth stage, the corn plants prematurely decline, or the maturity process is terminated before entering the maturity stage, the grouting time is shortened, the dry matter accumulation is reduced, and the 1000-grain weight, bulk density, yield and quality are reduced.
3. Damage to tassels and ears
During the booting stage and during the loose powder process, high temperatures may cause damage to the corn tassel. When the temperature continues to rise above 35 Â°C, it is not conducive to pollen formation, flowering loose powder is blocked, the tassel branch is smaller, the number is reduced, the floret is degraded, the anther is thin, the pollen activity is reduced, and the degree of damage increases with temperature and duration. Increased and prolonged. When the temperature exceeds 38 Â° C, the tassel cannot bloom and the loose powder is blocked.
4. Affecting the development of maize ears
High temperature also affects the development of the ear of maize, resulting in abnormal differentiation of various parts of the ear, delaying the silking of the ear, causing uncoordinated male and female, poor pollination and thinness of the grain.
In addition, high temperatures are prone to disease and decrease in yield and quality.
In the method of preventing high temperature heat damage of corn, in addition to breeding heat-resistant varieties, the following measures can be selected:
1. Artificially assisted pollination to increase the seed setting rate
During high temperature and drought, the natural loose powder, pollination and fertilization ability of corn decreased. If it encounters high temperature above 38 Â°C during flowering and loosening, it is recommended to use artificial auxiliary pollination to reduce the effect of high temperature on corn pollination and fertilization process. Improve the seed setting rate. Fresh pollen is usually collected at 8-10 am in the morning, and the pollen is pollinated with a homemade pollinator. The pollen should be used with the harvest. This method of crop production has a very significant effect on yield increase.
2. Properly reduce the density and plant in wide and narrow rows
Under the condition of low density, the contradiction between individuals competing for water and fertilizer is small, the individual is healthy and strong, and the ability to resist high temperature damage is strong, which can alleviate the heat damage. Under high-density conditions, wide and narrow row planting is beneficial to improve the ventilation and light transmission conditions in the field, cultivate robust plants, and increase the resistance to high temperature damage.
3. Scientific fertilization
In the fertilizer operation, increase the amount of organic fertilizer, focus on the application of basic fertilizer to promote early, pay attention to the application of trace elements, early maturing seedlings to promote strong stalks after corn emergence, and the main ear attack fertilizer to enlarge the ear before the tassel. In addition, combined with irrigation, the use of water to adjust fertilizer, accelerate fertilizer performance, improve plant nutrition, and enhance drought resistance. Foliar spray fertilizer can be used in high temperature period, which is beneficial to both cooling and humidification, and can supplement the water and nutrients necessary for corn growth and development.
4. Sprinkle water at a suitable time
High temperatures are often accompanied by droughts, and water is sprayed in advance during high temperatures to directly reduce field temperatures. At the same time, after irrigation, the corn plants get sufficient water, the transpiration is enhanced, and the canopy temperature is lowered, thereby effectively reducing the degree of high temperature stress, and also partially reducing the respiratory consumption caused by high temperature and reducing high temperature heat damage. Conditional spray water can be used to spray water directly onto the blade, and the temperature drop can reach 1-3 Â°C.
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