High Day or Night Temperatures Affect Cotton Yield Potential
• High day time temperatures can cause reduced photosynthesis, resulting in reduced cotton yield potential.
• High night time temperatures can increase plant respiration, consuming energy that could otherwise be used to increase
cotton yield potential.
• Sustained periods of above average day or night temperatures may explain why cotton yields are sometimes below
expectations.
Lower Than Expected Yields
Irrigated cotton growers are questioning why, in some
years, high yield potential cotton produces yields 20 to
30% below expectations. Ongoing research implicates
both higher than long-term average day and/or night
temperatures. High temperatures can decrease
photosynthesis and increase respiration, leading to
reduced seed production, reduced lint development, and
unexpectedly lower yields. While cotton typically
maintains canopy temperatures lower than air
temperatures, high humidity, coupled with high air
temperature, could lead to canopy temperatures above
the optimum.
Observations from 2016
Georgia farmers with irrigated cotton typically expect 3bale cotton yields. When their 2016 crop yielded 1100 to
1200 pounds per acre they were disappointed and
surprised. John Snider, cotton physiologist, University of
Georgia, says sustained high temperatures may have
contributed to the lower than expected yields.
"If we have high day time temperatures that are reducing
photosynthesis and high night time temperatures that
are increasing respiration, that can reduce productivity,"
he says. "When we have these high temperatures, I've
seen lower seed numbers, indicating reduced fertilization
efficiency. Plants may produce the same number of bolls,
but fewer seeds per boll result in smaller bolls and lower
lint production. When heat stress is combined with insect
and disease issues, the effects on yield are likely more
pronounced than any given stress alone." (Snider, J.,
personal conversation, October 17, 2016) An analysis of temperature extremes from June 1 to
September 1, 2016 (a year when numerous Georgia
cotton growers harvested lower than expected yields),
compared to the 5-year average temperatures, may
indicate that sustained higher than normal temperatures
can negatively affect cotton yields. Figure 1 shows the
number of days during the 2016 growing season that
temperatures exceeded the 5-year average. Figure 2
indicates June 1 to September 1 seasonal high, low, and
average temperature trends compared to the 5-year
average. Figure 1: Number of days during the 2016 growing season (June 1 to
September 1) that a given temperature parameter exceeded the previous
five year average (2011 to 2015). Dashed line indicates the point at which
the number of days above the five year average is equal to the number of
days below the five year average. In general, all temperature parameters
were higher for a greater percentage of the growing season in 2016 when
compared with the five year average (Especially Tmax). Data were
obtained from the University of Georgia Weather Network Station located in
Tifton, GA (http://www.georgiaweather.net/). Some growers also experienced reduced yield even when
seed production was normal. Snider stated, "If high
temperatures cause cotton to accumulate the same heat
units over a shorter period of time during fiber
development, this can result in reduced fiber quality and
yield. If plants have normal seed and boll numbers and
still experience lower yields, there could have been an
effect of high temperature on fiber development." High Day or Night Temperatures Affect Cotton Yield Potential
almost 50% in the number of flower buds per plant, thus
reducing the plant's ability to reach optimum yield potential. Effects of Day Time Heat Stress
Heat stress on cotton, caused when cotton canopy temperatures rise
above 82.4 oF, can reduce overal lint yields, delay crop maturity, and
reduce lint quality. Air temperatures are typically significantly higher than
canopy temperatures. Optimal performance occurs at canopy temperatures
below 82.4 oF and serious yield losses can result once canopy
temperatures exceed 86 oF. When canopy temperatures exceed 86 oF,
flowers produce little or no pollen which leads to abortion of young 3-5 day
old bolls. Young squares are also damaged, leading to low fruit retention.
These damaged squares typically do not abort, but develop into smaller
flowers that do not fully open, produce sterile anthers, and have what
appears to be an elongated stigma. This is actually an illusion that results
because the filaments supporting anthers fail to grow and elongate
properly while the stigma grows more or less normally.2
Management
Figure 2: Seasonal trends during the 2016 growing season (June 1 to
September 1; solid line) versus the previous five year average (2011 to
2015; dotted line) for daily minimum (Tmin), maximum (Tmax), and
average air temperature (Tave). Data were obtained from the University of
Georgia Weather Network Station located in Tifton, GA
(http://www.georgiaweather.net/). Growth Chamber Studies
Scientists at the University of Arkansas exposed cotton plants
to normal (89.6 oF day time temperatures and 75.2 oF night
time temperatures) and normal day time temperature but
increased (86 oF night time temperatures) for 7 days following
pinhead square stage (approximately 4 weeks after planting). 1
Although the cotton was not taken to yield, the growth
chamber studies showed significant effects on crop
productivity brought on by the higher night time
temperatures. Plants grown with higher night time
temperatures had 23% and 36% lower photosynthesis rates
compared to the control, 1 and 7 days after treatment
initiation, respectively. Respiration in the heat-stressed plants
increased 54% compared to the control on the first night.
Seven days into the trial, heat-stressed plants had a 68%
higher respiration rate compared to the control. 1 Further
analysis of the heat-stressed plants showed reduced
carbohydrate content in the flower buds and a decrease of
Cotton growers, particularly those growing cotton without irrigation, may
be able to hedge against reduced yield potential caused by high
temperatures by selecting varieties that are identified as being more heat
tolerant, although information on heat tolerance of available cotton
varieties is limited and is an area where additional research is needed.
Heat and drought stress can occur simultaneously, even in irrigated fields
when ambient temperatures are high and crop water use rates exceed
irrigation system capabilities. It may also be possible to avoid heat stress
in some fields by stretching out planting dates or by planting earlier
maturing varieties that may pollinate before high temperatues occur.
Agronomist point out; however, that predicting high temperature extremes
prior to planting is nearly impossible. They generally recommend selecting
varieties with high yield potential with good insect and disease resistance
and planting within the time window established for a given region for
normal cotton production.
Sources
1Loka,
D.A., and Oosterhuis, D.M., 2016. Increased night temperatures during cotton's early
reproductive stage affect leaf physiology and flower bud carbohydrate content decreasing
flower bud retention. Journal of Agronomy and Crop Science. 1 Agro Crop Sci (2016) ISSN
0931-2250.
2Brown, P. 2008. Cotton heat stress. AZ1448. The University of Arizona. cals.arizona.edu.
Snider, J.L., Oosterhuis, D.M., Skulman, B.W., and Kawakami, E.M. 2009. Heat stressinduced limitations to reproductive success in Gossypium hirsutum. Phuysiologia Plantarum.
137: 125-138.
Web sources verified 10/18/2016. 161017142834
For additional agronomic information, please contact your local seed representative. This
publication was developed in partnership with Technology Development & Agronomy by
Monsanto. Individual results may vary, and performance may vary from location to location and
from year to year. This result may not be an indicator of results you may obtain as local growing,
soil and weather conditions may vary. Growers should evaluate data from multiple locations and
years whenever possible.
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