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Agronomic Crops Network

Ohio State University Extension


How Climate Affects Corn Production


Corn can survive brief exposures to adverse temperatures―low-end adverse temperatures being around 32 degrees Fahrenheit and high-end ones being around 112 degrees Fahrenheit. Growth decreases once temperatures dip to 41 degrees Fahrenheit or exceed 95 degrees Fahrenheit. Optimal temperatures for growth vary between day and night, as well as over the entire growing season. For example, optimal daytime temperatures range between 77 and 91 degrees Fahrenheit and optimal nighttime temperatures range between 62 and 74 degrees Fahrenheit. The optimal average temperatures for the entire crop growing season, however, range between 68 and 73 degrees Fahrenheit. 

Even though corn seeds germinate and grow slowly at about 50 degrees Fahrenheit, the first spring planting dates usually begin when the average air temperatures reach 55 degrees Fahrenheit and soil temperature at seed depth is more favorable for seedling growth. Poor germination resulting from below normal temperatures is the greatest hazard of planting too early. The growing point of germinating seedlings remains below or near the soil surface, and usually is not vulnerable to freeze damage until plants reach the five- to six-leaf collar stage. By this time, corn is about 10-inches tall and the probability of freezing temperatures greatly decreases. The loss of leaves from frost generally does not seriously injure small plants, although such loss may delay plant development. 

Temperatures less than 40 degrees Fahrenheit reduce photosynthesis, even if the only symptom is a slight loss of leaf color. Frost injury symptoms may appear on leaves even when nighttime temperatures do not fall below the mid-30s; radiational cooling can lower leaf temperatures to several degrees below air temperatures on a clear, calm night. If frost kills leaves but not stalks before physiological maturity (black layer formation) in the fall, sugars usually continue to move from the stalk into the ear. However, yields are generally lower, and harvest moisture may be high because of high grain moisture at the time of frost and slow drying rates following premature death. 

High temperature stress during ear formation, reproduction, and grainfill can reduce yield, but temperatures less than 100 degrees Fahrenheit usually do not cause much injury if soil moisture is adequate. Under rain-fed conditions, corn usually begins to stress when air temperatures exceed 90 degrees Fahrenheit during the tasseling-silking (pollination) and grainfill stages. Corn yield may be reduced 1.5 bushels per acre for each day the temperature reaches 95 degrees Fahrenheit, or higher, during pollination and grainfill. Extended periods of hot, dry winds may cause tassel blasting and loss of pollen. Pollen shed usually occurs during cooler morning hours, however, and conditions severe enough to cause this problem are unusual in Ohio. 


A corn crop in Ohio typically uses 20 to 22 inches of water during the growing season. Water requirements of corn vary according to the stage of development, as shown in Table 4-1. Corn reaches its peak water use during pollination, when plants are silking. 

Excessive rainfall, resulting in flooding and ponding of soils, may cause serious injury to a corn crop depending on its stage of development. The major stress caused by flooding and ponding is a lack of oxygen needed for the proper function of the root system. When plants are very small (prior to six-leaf collar stage), they generally are killed after about five or six days of submersion. Death occurs more quickly (within two to four days) if the weather is hot, because warm temperatures speed up the biochemical processes that use oxygen, and warm water has less dissolved oxygen. Cool weather, on the other hand, may allow plants to live for more than a week under flooded conditions. 

Table 4-1: Water Use Rates for Corn at Different Growth Stages.

Growth Stage  Water Use Rate, Inches/Day 
Prior to 12-leaf stage  < 0.20
12-leaf  0.24
Early tassel  0.28
Silking  0.3
Blister kernel  0.26
Milk  0.24
Dent  0.2
Full dent  0.18

As soon as plants reach the six- to eight-leaf collar stage, and the plant’s growing point is above the soil surface, plants can tolerate a week or more of standing water―not necessarily without harm. In older plants, total submersion may increase disease incidence, and plants will suffer from reduced root growth and function for some days after the water recedes. Tolerance of flooding generally increases with plant age, but reduced root function resulting from a lack of oxygen is probably more detrimental to yield before and during pollination than during rapid vegetative growth or grainfill. 

Nutrient uptake is also reduced in soils saturated by excessive rainfall. Not only does poor aeration inhibit effective root development and function, but the anaerobic conditions associated with saturated soils promote denitrification. Frequent rainfall can also cause nitrate leaching. 

For crop moisture to be adequate, available soil moisture must be more than sufficient to meet the atmospheric evaporative demand. On windy, hot, sunny days with low humidity, evaporation demand on a crop is high and a high amount of available soil moisture must be present if the crop is to avoid stress. Under cloudy skies, high humidity, and cooler temperatures, atmospheric evaporative demand is low and plants can get by with lower amounts of available soil moisture. 

The soil must provide a corn crop with enough water to offset the amounts lost through transpiration. If these needs are not met, the plant will wilt. Table 4-2 shows the effect of drought on corn grain yield from four consecutive days of visible wilting. Through the late vegetative stage (the end of June in normal years), corn is fairly tolerant of dry soils. Mild drought during June may even be beneficial because roots generally grow downward strongly as surface soils dry, and the crop benefits from the greater amount of sunlight that accompanies dry weather. From the two weeks before through the two weeks following pollination, corn is very sensitive to drought, however, and dry soils during this period may cause serious yield losses. 

Most of these losses result from pollination failure, and the most common cause is the failure of silks to emerge from the end of the ear. When this happens, the silks do not receive pollen; thus, the kernels are not fertilized and will not develop. Drought later in grainfill has a less serious effect on yield, though root function may decrease and kernels may abort or not fill completely. 

Table 4-2: Effects of Drought on Corn Yield During Several Stages of Growth*. 

Stage of Development  Percent Yield Reduction 
Early vegetative  5 to 10 
Tassel emergence  10 to 25 
Silk emergence, pollen shedding  40 to 50 
Blister  30 to 40 
Dough  20 to 30