The heat wave is rolling in most of the central and eastern regions, and the strongest temperature continues this year. It is expected that three days (20-22 days), Huanghuai, Jianghuai, Jianghan, Jiangnan, the eastern Sichuan Basin, and the southeastern part of North China will continue to have a wide range of high temperatures, including Chongqing, eastern Sichuan, southwestern Shaanxi, and northern Henan. The temperature can reach 37 ~ 39 ° C, the local area will even reach 40 ° C or above, need to pay attention to prevention.

The high temperature weather in the central and eastern regions will continue for three days. The Central Meteorological Observatory estimates that from the 20th to the 21st, parts of Huanghuai, Jianghuai, Jianghan, Jiangnan, Sichuan Basin, southern and eastern North China, southwestern Shaanxi, eastern Guizhou, Chongqing, and Xinjiang Nanjiang Basin will continue to appear above 35 °C. The high temperature weather can reach 40 °C locally. The Central Meteorological Observatory continued to issue high-temperature yellow warnings at 06:00 on the 20th.

Among them, the highest temperature in southwestern Shaanxi, southern and eastern North China, Huanghuai, Jianghuai, Jianghan, Jiangnan, northern China, eastern Sichuan, eastern Guizhou, Chongqing, Xinjiang Nanjiang Basin, etc., the southwest of Shaanxi, Shandong Some areas in the west, north of Henan, southern Anhui, southeastern Hubei, northeastern Hunan, northwestern Jiangxi, eastern Sichuan, Chongqing, and Xinjiang southern Xinjiang basin have a maximum temperature of 37-39 °C and a local area of ​​40 °C.

The index of heat damage in maize is based on moderate heat damage, 36°C at seedling stage, 32°C at reproductive stage, and 28°C at maturity. Temperatures above 32 °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 °C, the production is reduced by 11.9%; the moderate heat damage is 33 °C, the production is reduced by 52.9%; the severe heat damage is 36 °C, which will result in the production. The highest temperature of 38-39 °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 effects of high temperature on corn growth are as follows:

1. The 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 ° 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 °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 ° C, the tassel cannot bloom and the loose powder is blocked.

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.

Ways to prevent high temperature hazards:

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 °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. Appropriately 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 °C.

The continuous high temperature weather has seriously adversely affected the growth and development of crops. So, what is the hazard to the current corn caused by high temperature? What kind of preventive measures should be taken? According to Jiang Hongfei, director of Jiangsu Tomorrow Seed Industry Research Introduction,

There are four types of high temperature heat damage in corn:

(1) Delayed hazard

During the growth and development of corn, it is subjected to different degrees of high temperature damage for a long time, which hinders photosynthesis and weakens enzyme activity, resulting in slower growth and development.

(2) Obstacle type hazard

During the differentiation period from the reproductive organs of maize to the heading and flowering stage, it suffers from abnormal high temperature hazards, which causes damage to the reproductive organs, resulting in infertility or partial infertility and reduced production. This kind of hazard has a short time, but it is difficult to return to normal after being victimized. It is characterized by baldness, lack of grain, lack of line or even no ear and reduced yield.

(3) poor growth type

After the corn is damaged in the vegetative growth period, the height is reduced, the number of leaves is reduced, the number of grains is reduced, and the ear is shortened. However, there is no significant delay in maturity, and 1000-grain weight has little effect. Mainly due to the small number of grains, weak growth and reduced production.

(4) Mixed type

In the same year, the high temperature in the early stage caused the growth and development to be poor, and in the later stage, the low temperature damage caused the filling to be slow, which caused the corn to be seriously reduced.

When talking about the impact of high temperatures on current corn growth, Shi Hongfei said,

1. Corn is currently in the critical period of ear differentiation. In case of high temperature or drought, the ear differentiation may be stagnant or abnormal, resulting in the appearance of abnormal spikes without ear or silk in the later stage;

Second, the period from the big trumpet period to the heading is the period when the corn needs the maximum amount of fertilizer and water. If the drought is absent during this period, it will affect the normal flowering of the tassel and the extraction of the fringe of the ear, causing the tassel to advance and the silking delay, the vitality of the pollen. Weak, filaments are easy to wither, resulting in the inability to pollinate and fertilize and appear empty stalks with spikes and no grains.

In addition, high temperatures are prone to disease and decrease in yield and quality.

Abnormality of ear differentiation in maize

In corn production, abnormalities in the differentiation of maize ears are often caused by high temperatures, and this abnormal phenomenon can cause a significant reduction in corn yield.

Multi-ear phenomenon: Normally, each corn plant generally differentiates into a strong ear with a small amount of double ears. However, some plots have abnormal multi-spots. From the 5th to the 9th section of the corn, 2 to 3 spikes grow, and many of them reach 5 to 6 spikes. Spikes, multiple spikes, and filigree.

Banana stick phenomenon: In one or two leaf axils in the middle of some varieties of plants, 3 to 5 small earlets grow at the same time, and the stems and stems are connected, forming bananas with little or no agglomeration. The masses call it "banana". corn".

Empty stalk phenomenon: 2 to 5% of the empty stalk rate in the corn field is a normal phenomenon, but in some years, some varieties, some plots, the empty stalk rate is above 10%, and the individual is above 30%.

Poor solidity: Normal annual landscape, the average grain per ear is more than hundreds of grains, but sometimes there are several abnormal phenomena: 1 spikes are rare, the average is only 10 to 50 per ear; 2 bald top is serious, and the bald part is It is relatively large, some of which are 50% of the length of the ear, and the severity is 70-90%. 3 There are many empty ears, and the ear is very long from the outside, but one is not yet knotted, and some plots and varieties have an empty ear rate of 30%. the above. (Yuege Agricultural Resources Network Integrated China Weather Network, Seed Industry Business Network, WeChat Public Number)

This article URL: What are the hazards of high temperature continuous corn? How to deal with hot weather in corn planting

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