Corn high-temperature heat damage can cut yields by 30% or even cause total crop failure; see the prevention methods here
This year there will be 40 days of dog days (the hottest period of summer), which is a serious challenge for corn growth, so what exactly is the harm of high-temperature heat damage to corn? How can these harms be prevented?
High-temperature heat damage causes corn yield reduction or total crop failure
High-temperature heat damage is a natural disaster encountered in corn production. After late July, summer corn in most regions is in the critical period of transition from vigorous vegetative growth to reproductive growth, and is very sensitive to climate factors such as light, fertilizer, water, heat and air. When corn is under meteorological conditions with a daily average temperature greater than or equal to 35°C lasting more than 5 days, and ineffective rainfall lasting more than 8 days, high-temperature heat damage is bound to occur.
During this period, if suitable temperature, light and moisture conditions occur in sync with corn growth and development, it will be beneficial to growth and development and increase yield. On the contrary, if continuous high-temperature drought or disaster weather conditions such as cloudy and rainy days with insufficient light are encountered, growth and development will be seriously affected, leading to reduced yield. In severe cases, yield can be reduced by more than 30%, and in even more severe cases it may lead to total loss of production and no harvest.
Grading of high-temperature heat damage in corn
The heat damage index for corn is based on moderate heat damage: 36°C at the seedling stage, 32°C at the reproductive stage, and 28°C at the maturity stage. During the flowering stage, temperatures above 32°C are unfavorable for pollination. Based on the average temperature over the whole growth period, mild heat damage is 29°C, with an 11.9% yield reduction; moderate heat damage is 33°C, with a 52.9% yield reduction; severe heat damage is 36°C, which will cause total loss of production. A maximum temperature of 38-39°C causes high-temperature heat damage, and the longer it lasts, the more severe the damage and the more difficult the recovery.
Effects of high temperature on corn growth
1. Affects leaf photosynthesis
Under high-temperature and drought conditions, to prevent the chloroplast structure from being damaged, leaves curl, the leaf photosynthetic area decreases, and the photosynthetic capacity of the leaves is greatly reduced.
2. Shortens the growth period
High temperature forces various physiological and biochemical reactions in the corn growth process to accelerate, shortening each growth stage. For example, the differentiation time of the female ear is shortened, the ear becomes smaller, and the number of florets differentiated on the tassel decreases. In the late growth stage, high temperature causes corn plants to senesce and die prematurely.
3. Affects the development of female and male ears
At high temperatures above 35°C, tassel branches become smaller and fewer in number, florets degenerate, anthers become shriveled, and pollen vigor decreases. When the temperature exceeds 38°C, the tassel cannot flower and pollen shedding is blocked. High temperature causes abnormal differentiation of various parts of the female ear, delays silking of the female ear, and causes poor synchronization between male and female, poor pollination and seed setting, and shriveled grains. In addition, high temperature easily triggers diseases and reduces both yield and quality.
Methods to prevent high-temperature heat damage in corn
Among the methods to prevent high-temperature heat damage in corn, in addition to selecting heat-tolerant varieties, the following measures can also be chosen:
1. Artificial supplementary pollination to increase the seed-setting rate
During periods of high temperature and drought, the natural pollen shedding, pollination and fertilization seed-setting ability of corn all decline to some extent. If continuous high-temperature weather above 38°C is encountered during the flowering and pollen-shedding stage, it is recommended to use artificial supplementary pollination to reduce the impact of high temperature on the pollination and fertilization process of corn and increase the seed-setting rate. Generally, fresh pollen is collected from 8-10 a.m., and a homemade pollinator is used to pollinate the silks; the pollen should be used immediately after collection. In seed production fields, the yield increase effect of using this method is very significant.
2. Appropriately reduce density and adopt wide-narrow row planting
Under low-density conditions, competition among individual plants for water and fertilizer is relatively small, individual development is robust, the ability to resist high-temperature damage is stronger, and high-temperature heat damage can be reduced. Under high-density conditions, adopting wide-narrow row planting helps improve field ventilation and light transmission conditions, cultivate robust plants, and increase resistance to high-temperature damage.
3. Scientific fertilization
In fertilizer management, increase the amount of organic fertilizer used, focus on applying base fertilizer broadly to promote early development, and attach importance to the application of trace elements. After corn emergence, apply seedling fertilizer early to promote strong stalks, and from the large trumpet stage to before tasseling, focus on ear fertilizer to increase ear size. In addition, combined with irrigation, adopt the method of regulating fertilizer with water to accelerate the exertion of fertilizer effects, improve the plant's nutritional status, and enhance drought resistance. During high-temperature periods, foliar fertilizer spraying can be used, which not only helps lower temperature and increase humidity, but also supplements the water and nutrients necessary for corn growth and development.
4. Sprinkler irrigation at the appropriate time
High temperature is often accompanied by drought. Spraying irrigation water in advance during high-temperature periods can directly lower field temperature. At the same time, after irrigation, corn plants obtain sufficient water, transpiration is enhanced, and the canopy temperature is lowered, thereby effectively reducing the degree of high-temperature stress. It can also partially reduce respiratory consumption caused by high temperature and mitigate high-temperature heat damage. Where conditions permit, sprinkler irrigation can be used to spray water directly onto the leaves, and the cooling range can reach 1-3°C.