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

ManagementSouth Africa Update and the New New Leader G5
February 24, 2017
Editors Eric Sfiligoj and Dan Jacobs discuss the recent visit to South Africa by sister magazine AgriBusiness Global and the Read More
Fall Creek Watershed
StewardshipUpdate: Nutrient Stewardship In Indiana Requires Cool, Clean Collaboration
February 24, 2017
Update: The application deadline for NCRS funding has been extended to March 17, 2017. Green leaves sparkle in the sunlight. Trees Read More
Measuring Bulk Tanks
StewardshipMeister Media Among 2017 Award Winners Presented By The Pesticide Stewardship Alliance
February 21, 2017
The Pesticide Stewardship Alliance (TPSA) held its annual conference in San Diego, CA, earlier this month where three awards were Read More
Roy Blunt
LegislationARA Recognizes Blunt, Heitkamp For Legislative Efforts Supporting Agriculture
February 17, 2017
Agricultural industry continues to face federal regulatory challenges. Thankfully, agriculture’s allies in the U.S. Senate stepped forward. The Agricultural Retailers Read More
Trending Articles
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
Precision AgTrimble Debuts End-to-End FMIS Platform
November 28, 2016
October’s inaugural PrecisionAg Vision Conference left this author with many thoughts and things to ponder in the coming months. Probably Read More
CHS Primeland
CropLife 100The 2016 CropLife 100 Report: Reviewing The Many Bulls And Bears Impacting This Year’s Marketplace
November 28, 2016
For virtually all of 2016, the nation was wholly focused on the big Presidential election. Some folks aligned themselves with Read More
Latest News
ManagementSouth Africa Update and the New New Leader G5
February 24, 2017
Editors Eric Sfiligoj and Dan Jacobs discuss the recent visit to South Africa by sister magazine AgriBusiness Global and the Read More
Fall Creek Watershed
StewardshipUpdate: Nutrient Stewardship In Indiana Requires Cool, …
February 24, 2017
Update: The application deadline for NCRS funding has been extended to March 17, 2017. Green leaves sparkle in the sunlight. Trees Read More
Greenleaf Technologies TADF03-D Dual Fan Nozzle
NozzlesSix Greenleaf Nozzles Approved For XtendiMax With Vapor…
February 22, 2017
Greenleaf Technologies has announced that six of its TurboDrop D Series nozzles have been approved for use with Monsanto’s XtendiMax Read More
Winter Wheat
Industry NewsTiger-Sul Hires Manitoba And Eastern Canada Account Man…
February 22, 2017
Tiger-Sul, a global leader in sulphur fertilizers and crop performance products, has announced that sales veteran Trevor Loewen has joined Read More
NFMS 17 Hagie Sprayer
Eric SfiligojThe Read From Louisville: Uncertain
February 22, 2017
By the time this column appears across the country, the annual Commodity Classic will be in full swing. This means Read More
SprayersApache 1000 Series Sprayer Earns 2017 EquipmentWatch Hi…
February 21, 2017
ET Works has been named a winner in the 2017 EquipmentWatch Highest Retained Value Awards program, the industry’s only award Read More
Measuring Bulk Tanks
StewardshipMeister Media Among 2017 Award Winners Presented By The…
February 21, 2017
The Pesticide Stewardship Alliance (TPSA) held its annual conference in San Diego, CA, earlier this month where three awards were Read More
John Reifsteck
CropLife 100GROWMARK’s Reifsteck Earns NCFC Director Of The Y…
February 21, 2017
GROWMARK Chairman of the Board and President John Reifsteck has earned the prestigious Director of the Year Award from the Read More
Roy Blunt
LegislationARA Recognizes Blunt, Heitkamp For Legislative Efforts …
February 17, 2017
Agricultural industry continues to face federal regulatory challenges. Thankfully, agriculture’s allies in the U.S. Senate stepped forward. The Agricultural Retailers Read More
LegislationThe Fertilizer Institute Commends Senate On Confirmatio…
February 17, 2017
The Fertilizer Institute (TFI) President Chris Jahn issued the following statement on the Senate confirmation of Oklahoma Attorney General Scott Read More
Trump, Senate, Cabinet
LegislationBREAKING: Trump EPA Nominee Scott Pruitt Confirmed by S…
February 17, 2017
Scott Pruitt, who as Oklahoma’s attorney general spent years suing the Environmental Protection Agency over its efforts to regulate various Read More
ManagementFebruary Road Trip Edition
February 17, 2017
Editors Paul Schrimpf and Eric Sfiligoj discuss their recent visits to Indiana and Kentucky. Read More
Heritage Cooperative Finished Building Aerial
ManagementHeritage Cooperative, Agland Co-op Approve Merger
February 17, 2017
Agland Co-op and Heritage Cooperative stockholders have both approved the merger agreement between Agland Co-op and Heritage Cooperative. Now begins Read More
LegislationARA Fly-In: Ag Retail Descends on Capitol Hill, Lawmake…
February 15, 2017
More than 100 agricultural retailers, distributors and suppliers headed to Capitol Hill Tuesday morning for the Agribusiness Congressional Fly-in, according to a Read More
Untreated soybean seed Heartland Coop
Seed/BiotechMarrone Bio Innovations, Groundwork BioAg Bio-stacked M…
February 13, 2017
Marrone Bio Innovations, Inc. and Groundwork BioAg, Ltd have announced successful seed treatment field trials of the world’s first all-biological Read More
NL5000 With G5 Technology
SpreadersNew Leader Introduces NL5000 Dry Nutrient Applicator Wi…
February 13, 2017
New Leader, a division of Highway Equipment Company (HECO), has announced the next generation of spreading technology with the NL5000 Read More
Fertilizer Storage
Crop InputsThe State Of The Fertilizer Industry
February 9, 2017
He’s all hat, no horse.” It’s a humorous way of describing a person who tells a good story, but is Read More
CropLife 100Pinnacle Agriculture Agrees To Credit Agreement Amendme…
February 9, 2017
Pinnacle Operating Corp. has entered into an amendment (the “Amendment”) to its First Lien Credit Agreement that will provide for, Read More