Global high-temperature weather is becoming increasingly frequent. During the period from corn jointing to tasseling and silking, which is a critical stage for the transition from vegetative growth to reproductive growth, high temperatures can affect corn growth and yield formation in multiple ways.
Direct Impacts
- Obstructed Reproductive Growth and Decreased Seed Setting Rate
The stages of corn tasseling (emergence of male inflorescences), silking (exposure of female ear filamentous stigmas), and pollination are extremely sensitive to high temperatures (the critical temperature is usually 32~35℃, and a continuous period of more than 3 days will have a significant impact).
- Abnormal Development of Male Inflorescences
High temperatures accelerate the meiosis of pollen mother cells, resulting in incomplete development of pollen grains, decreased viability (normal pollen survives only 1~2 hours at 38℃), and even pollen abortion, which affects the amount of pollen dispersal.
- Delayed or Poor Silking of Female Ears
High temperatures may cause a mismatch between the development speed of female ears and male inflorescences (silking of female ears is usually 2~5 days later than tasseling of male inflorescences). If high temperatures occur during the silking stage, the vitality of stigmas decreases, making it difficult to capture pollen. In severe cases, the differentiation of female ears is obstructed, resulting in “empty stalks” or “bare tips” (lack of grains at the top of ears).
- Reduced Pollination and Seed Setting Rate
The combination of decreased pollen vitality and insufficient stigma activity leads to incomplete fertilization, eventually resulting in sparse grains in ears, with yield reduction ranging from 10% to 30% (even total crop failure in extreme cases).
Indirect Impacts
- Water Stress and Physiological Metabolism Disorders
If irrigation is not timely or soil moisture is insufficient (such as in dry farming areas or areas with imperfect irrigation facilities), drought stress is likely to occur.
- Plant Wilting and Impaired Photosynthesis
Under high temperatures, the stomatal conductance of leaves decreases (stomata close to reduce transpiration), resulting in reduced carbon dioxide absorption and a decrease in photosynthesis rate. At the same time, when the transpiration water loss of leaves exceeds the water absorption capacity of roots, plants wilt due to water shortage, and in severe cases, leaves turn yellow and growth stagnates.
- Reduced Accumulation of Photosynthetic Products
Under high-temperature stress, corn plants will prioritize the distribution of photosynthetic products to roots (to enhance water absorption capacity) for survival rather than to grains, resulting in reduced transportation of dry matter to grains, which ultimately affects ear weight and grain weight.
Derivative Impacts
- Aggravated Pests and Diseases and Lodging Risk
High temperature and high humidity (if there is periodic precipitation) may change the microclimate in the field, inducing or aggravating pests and diseases.
- Diseases
High temperatures are conducive to the spread of corn northern leaf blight and stalk rot (bacterial/fungal infection). The increase of leaf spots will further weaken photosynthetic capacity. At the same time, the decrease of root vitality may aggravate root rot.
- Pests
High temperatures promote the reproduction of pests such as corn borers and aphids (for example, the reproduction cycle of aphids is shortened at temperatures above 30℃).
How To Help Corn Overcome It
To prevent the adverse effects of high temperatures, the following measures can be taken:
- Irrigation for Cooling and Timely Water Supplement
According to the growth of seedlings and changes in soil moisture, timely apply small and shallow irrigation to maintain the normal tasseling, pollen dispersal, grouting and seed setting of plants. Where conditions permit, drip irrigation, sprinkler irrigation, furrow irrigation and other irrigation measures can be adopted to replenish water in time; in areas without conditions, methods such as staggered ridge irrigation and alternate ridge irrigation can be used to reduce water consumption and lower the field temperature. Choose the right time: conduct sprinkler irrigation before 9 a.m. and after 6 p.m., avoiding high-temperature periods at noon to avoid harming corn.
- Artificial Supplementary Pollination
For fields with delayed development due to drought, timely conduct artificial supplementary pollination to improve the seed setting rate.
- Pest and Disease Control
Strengthen monitoring and early warning, pay close attention to the occurrence trends of pests and diseases such as corn borers, armyworms, aphids and leaf spot diseases, and carry out emergency control and unified control in a timely manner.
