Drought 2012: How Extended High Heat Disrupts Corn Pollination

Corn was originally a tropical grass from the high elevation areas of central Mexico about 7,400 feet above sea level, 2,000 feet higher than Denver. Today, corn still prefers conditions typical of that area – warm daytime temperatures and cool nights. Areas that consistently produce high corn yields share some significant characteristics. These areas – central Chile, the west slope of Colorado, etc. – are usually very bright, clear, high light intensity areas with cool nights.

Corn maximizes its growth rate at 86°F. Days with temperatures hotter than that cause stress. In the high yield areas, cool night temperatures – at or below 50°F – reduce respiration rates and preserve plant sugars, which can be used for growth or reproduction, or stored for yield. These are optimum conditions for corn, and interestingly, are fairly typical for areas around central Mexico where corn is native.

This year, in the prairie states and in the Cornbelt, conditions have been dramatically less than optimal.

In years when we get high day and nighttime temperatures coinciding with the peak pollination period, we can expect problems. Continual heat exposure before and during pollination worsens the response. Daytime temperatures have consistently stayed in the upper 90s to low 100s.

The high humidity, which helps reduce crop water demand, also increases the thermal mass of the air – and provides extra stored heat and insulation at night.

Corn is a “C4 Photosynthesis” plant, making it extremely efficient at capturing light and fixing CO2 into sugars. One drawback of this system is that with high daytime temperatures, the efficiency of photosynthesis decreases, so the plant makes less sugar to use or store. High nighttime temperatures increase the respiration rate of the plant, causing it to use up or waste sugars for growth and development. This results in the plant making less sugar but using up more than it would during cooler temperatures.

Heat, especially combined with lack of water, has devastating effects on silking. If plants are slow to silk, the bulk of the pollen may already be shed and gone. Modern hybrids have vastly improved “ASI” or anthesis-silk interval (the time between mid-pollen shed and mid silk). Regardless, in some dryland fields we see seed set problems because of “nick” problems between pollen and silking.

Even in some stressed areas within irrigated fields (extreme sandy spots, hard pans or compaction areas where water isn’t absorbed and held, and some “wet spots”) we can see stress-induced slow silking and resulting seed set issues. Historically, this has been the most important problem leading to yield reduction, particularly in stressful years. Once silks begin to desiccate, they lose their capacity for pollen tube growth and fertilization.

Even with adequate moisture and timely silking, heat alone can desiccate silks so that they become non-receptive to pollen. While this is a bigger problem when humidity is low, it is apparent that it is happening this year, especially on hybrids that silk quite early relative to pollen shed. Even with dew points in the 70s, when temperatures reach the high 90s to the100s, the heat can still desiccate silks and reduce silk fertility.

Heat also affects pollen production and viability. First, heat over 95°F depresses pollen production. Continuous heat, over several days before and during pollen-shed, results in only a fraction of normal pollen being formed, probably because of the reduced sugar available. In addition, heat reduces the period of pollen viability to a couple hours (or even less). While there is normally a surplus of pollen, heat can reduce the fertility and amount available for fertilization of silks. It’s been shown (Herrero and Johnson, see Resources) that prolonged exposure to temperatures reduced the volume of pollen shed and dramatically reduced its viability.

For each kernel of grain to be produced, one silk needs to be fertilized by one pollen grain.

A friend of mine, Dr. Jim Dodd of Professional Seed Research, sent me an e-mail after reading [this] article on “How Extended High Heat Disrupts Corn Pollination”. Jim, who is a much better botanist than I, reminded me of the effects of humidity alone on the pollination process.

Corn pollen is produced within anther sacs in the anther. The plant releases new, fresh anthers each morning, starting from near the top of the tassel, on the first day of shed, and proceeding downward over several days. The process of releasing the pollen from the anthers is called “dehiscence.” Dehiscence is triggered by the drop in humidity, as the temperature rises. However, when it is extremely humid and the humidity falls very little, dehiscence may not occur at all, or it may be delayed until late in the day. If one has breezes, while the humidity is still very high, the anthers may fall to the ground before pollen is released. If the temperature rises too high before pollen dehiscence occurs, the pollen may have reduced viability when it is shed.

A person experienced at hand pollination in corn will often see this happen. There will be anthers in a “tassel bag,” but little pollen. The usual solution to this is to wait a couple hours until the temperature rise reduces the humidity. However, this year we had some conditions where pollen was never released from the anthers. This can impact silk fertilization, particularly in open-pollinated situations.

Topics:

Leave a Reply

Management Stories

ManagementThink You Know Water? Take WinField United’s ‘Unchartered Waters’ Quiz Via NatGeo
March 22, 2017
Water is among our most precious resources, and arguably the hardest working, with just one percent available for human use, Read More
Corn Field
LegislationTFI Hopes Court Dismissal Is ‘Final Chapter’ Of Des Moines Water Works Lawsuit
March 20, 2017
The Fertilizer Institute (TFI) released the following statement from President, Chris Jahn on the March 17, 2017, federal court dismissal Read More
ManagementSnowstorms, Asset Sales, and Soybeans Prices
March 16, 2017
Editors Paul Schrimpf and Eric Sfiligoj discuss the weather, precision ag, crop protection company mergers, and commodity prices in this Read More
Management2017 Commodity Classic Review
March 10, 2017
Editors Paul Schrimpf and Eric Sfiligoj discuss what happened at the recent Commodity Classic in San Antonio. Read More
Trending Articles
AdjuvantsA New Weed-Control Era Begins: But First, One Last Obstacle
March 4, 2017
There is trepidation, there is reluctance, and there is excitement. Ag retailers feel it all about the new dicamba and Read More
LIFT Academy video screenshot
Crop InputsLIFT Agriculture Academy: A Q&A With West Central Distribution’s Dean Hendrickson
March 1, 2017
West Central Distribution recently launched its LIFT Agriculture Academy, a new, premiere training and professional development resource for West Central’s ag Read More
Farmer and aptop
Matt Hopkins10 Warning Signs Your Website Is Grossly Outdated
February 8, 2017
Your Website is often a visitor’s first impression of your ag retail business. A positive first impression can set the Read More
AgriSync
Matt Hopkins17 Agriculture Apps That Will Help You Farm Smarter In 2017
December 9, 2016
Ag professionals are working smarter, not harder, than ever before. Smart farming technologies have enabled them to reduce costs, maximize Read More
R4023 Sprayer, John Deere
CropLife 100Ag Retail Equipment Report: The Green Party Continues
December 7, 2016
In the annual race for sales in the ag retail equipment marketplace, the color schemes for participants are a little Read More
Mike Stern
Precision AgClimate Corp. CEO Talks Retailer Support For Digital Ag
December 1, 2016
CropLife Magazine’s sister publication, AgriBusiness Global, recently sat down with Mike Stern, CEO of The Climate Corp., following the Monsanto subsidiary’s Read More
Latest News
UncategorizedPrecision Ag, Iowa Water, and GM Corn Updates
March 24, 2017
Editors Paul Schrimpf and Eric Sfiligoj look at the state of precision agriculture, the dismissal of the Des Moines Water Read More
Pam Marrone
Crop InputsMarrone Bio Innovations Enters Biostimulants Market Wit…
March 23, 2017
Marrone Bio Innovations, Inc. is expanding beyond biopesticides and crop protection and into the biostimulant market by commercially launching Haven Read More
Nutrients for Life Foundation Teacher
FertilizerNutrients For Life Foundation Celebrates 10 Years Teach…
March 23, 2017
Those in agriculture know fertilizer is a vital ingredient to grow strong, productive crops. In fact, fertilizer is responsible for Read More
ManagementThink You Know Water? Take WinField United’s R…
March 22, 2017
Water is among our most precious resources, and arguably the hardest working, with just one percent available for human use, Read More
Corn Field
LegislationTFI Hopes Court Dismissal Is ‘Final Chapter’…
March 20, 2017
The Fertilizer Institute (TFI) released the following statement from President, Chris Jahn on the March 17, 2017, federal court dismissal Read More
Wheat Growers
Industry NewsWheat Growers CEO Dale Locken To Retire
March 20, 2017
CEO Dale Locken has announced that he plans to retire from Wheat Growers. Locken has served almost 15 years as Read More
Bayer Monsanto
Eric SfiligojBayer-Monsanto: Life, LibertyLink, And The Pursuit Of R…
March 20, 2017
As the calendar officially turns to spring, life is in full renewal mode. Flowers are blooming, birds are singing, and Read More
Corn Field
Crop InputsUltra Yield Micronutrients Acquires Kronos Micronutrien…
March 16, 2017
Ultra Yield Micronutrients, Inc. ”Ultra”, an affiliate of Cameron Chemicals, Inc., is pleased to announce that it has acquired the Read More
ManagementSnowstorms, Asset Sales, and Soybeans Prices
March 16, 2017
Editors Paul Schrimpf and Eric Sfiligoj discuss the weather, precision ag, crop protection company mergers, and commodity prices in this Read More
Soybean Field
Seed/BiotechBayer Invests $8.1 million In Soybean Advancement In Th…
March 16, 2017
Growers in Illinois and across the Midwest now have the added benefit of a state-of-the-art soybean research facility, increasing accessibility Read More
CHS
CropLife 100CHS Acquires Western Co-op Transport Association
March 16, 2017
CHS Inc., North America’s leading farmer-owned cooperative and a global energy, grains and foods company, has purchased Western Co-op Transport Read More
Young corn plants in soil
HerbicidesBest Management Practices To Control PPO-Resistant Weed…
March 14, 2017
Weeds resistant to the class of herbicides called protoporphyrinogen oxidase (PPO) inhibitors are spreading at a faster rate than weed Read More
Photo credit: The United Soybean Board/The Soybean Checkoff.
Eric SfiligojFungicide Resistance On The Horizon
March 13, 2017
For many years now, the agricultural market has struggled to keep ahead of an ever-growing number of herbicide-resistant weeds. According Read More
Management2017 Commodity Classic Review
March 10, 2017
Editors Paul Schrimpf and Eric Sfiligoj discuss what happened at the recent Commodity Classic in San Antonio. Read More
Farmer using AgriSync
ManagementMajor AgriSync Update Aims To Extend Ag Experts’ Power …
March 10, 2017
AgriSync announced a major update to its leading collaboration and service management tool for professional ag advisors and their farmer Read More
Agrible Pocket Spray Smart App
EquipmentNew Agrible Pocket Spray Smart App Alleviates Spraying …
March 10, 2017
There’s a new app to help farmers decide when to spray their fields. Pocket Spray Smart is a free iOS Read More
BPIA logo
Crop InputsBiological Products Trade Association Changes Name, Exp…
March 9, 2017
The Biological Products Industry Alliance (BPIA), formerly the BioPesticide Industry Alliance, is the new name of the rapidly growing U.S.-based Read More
BBI MagnaSpread Salford BBI
Equipment14 Fertilizer Spreaders For 2017
March 9, 2017
Application equipment manufacturers stressed flexibility and accuracy with this year’s crop of fertilizer spreaders. From AGCO’s TerraGator TG9300B and Case IH’s 810 Read More