Corn Yield Forecasts and Estimates

Agriculture and Natural Resources Extension
Iowa State University

Extension Lead(s)
(name, position, counties served, contact information)

Roger Elmore, Extension Corn Agronomist, Statewide
Department of Agronomy
2104 Agronomy Hall
Iowa State University
Office phone 515 294 6655
Cell Phone 515 450 2724

Your Position


POW #and Team

­­­­­__x__100 Corn and Soybean Production and Protection
­­­­­_____ 110 Dairy
­­­­­_____ 120 Farm and Business Management
­­­­­_____ 130 Horticulture: Commercial and Consumer
­­­­­_____ 140 Iowa Beef Center
­­­­­_____ 150 Iowa Pork Industry Center
­­­­­_____ 160 Natural Resources and Stewardship

ANR Priority(select all that apply)

­­­­­__x___Global Food Security and Hunger
­­­­­__x___Regional Food Systems
­­­­­_____Natural Resources & Environmental Stewardship
­­­­­_____Food Safety
­­­­­_____Sustainable Energy – Biofuels &Biobased Products
­­­­­_____Climate Change

Title of Success Story

Corn yield forecasts and estimates

Continuing Story

___x__ No                _____  Yes(If continuing, what story?)

Knowledge Areas:(USDA categories)


Desired Changes

Producers and agronomists learn techniques and pitfalls of estimating corn yields prior to harvest.  More accurate yield estimates stabilize grain market prices and contribute to more constant prices at the super market since so many products contain corn.

(Why is it important to address this issue with education? What are the desired changes?)

Corn  prices are based on supply and demand. Simply put, asmall crop harvest results in higher prices and a large crop in lower prices if all everything else remains the same.  The National Agricultural Statistics Service (USDA-NASS) forecastscorn yield on a monthly basis beginning in August with the final report published in January.  Corn prices fluctuate wildly in response to these reports. Farm radio broadcasters, television reporters, newspaper writers, all spend considerable time and energy reporting the newest yield numbers.Rumors spread quickly. Extension agronomists and economists attempt to add a realistic view on these yield estimates.  We wantthe producers, reporters, grain marketers, agronomists among others to have  a realistic view on yield  estimates.  This contributes to stabilized prices both at the grain elevator and at the super market.

(Outputs: activities, numbers reached, publications, products)

We discussed yield estimates at nearly every corn management meeting during the winter and spring. The discussion centeredon variables that affect accuracy of forecasted yields.
Recent outputs -among others - include:
Corn Field Guide p. 14:
Reduced 2010 Corn Yield Forecasts Reflect Warm Temperatures between silking and dent

Corn Development and September Yield Forecast, 2010:
Iowa Corn Yields 2010: Forecast, Methodology and Opinion:
Crop Advantage Series presentation to several hundred people:
Where did the yield go? 2010….
Yield estimates were discussed at two field days in August 2010 a month or more before corn maturity. At the Northeast Iowa Field Day, fifteen teams of 3 to 4 people assessed mature corn ears (from 2009 plant population trials) and estimated yield.  A total of 100 people heard the field day presentations.

RESULTS(Outcomes:  specific changes that occurred in Learning, Actions,Conditions; how outcomes were measured)

At the field day, yield estimates by different teams from the same set of corn ears differed by up to 80 bushels per acre; that’s more than a 30% change! Multiply that by Iowa’s 14 million acres and we’re talking about huge differences in corn supply from just one state. Grain marketers speculate on the yield estimates, buying and selling huge amounts of grain before it is even harvested.  Think about that! Yield estimates can vary dramatically and result in huge swings in corn and food prices even before harvest begins.  That is the danger in trusting yield estimates prior to maturity. The attached photo shows one of the teams estimating corn yield with an extension colleague. The articles listed above and field day presentations encouraged clients to carefully consider the value of yield estimates.

Public Value (now or future)
(Impact:  Who benefits beyond participants and how?  What conditions changed?)

More information on the pluses and minuses of yield forecasts and estimates levels the playing field for everyone from farmers to grain brokers. This leads to more stable grain market prices. Citizens will benefit since more stable grain prices contribute to more stable prices at super markets.

Major Partners or Collaborators

USDA-NASS, Iowa State University Extension, Reporters (local newspapers, regional and national magazines and newspapers, regional Radio and TV, Board of Trade, and National press).

Where story took place
(Region, campus, multi-regional)

Field days at Allee R&D farm and NE Iowa R&D farm.  Crop Advantage Series around the state in January, 2011

Fiscal Year


Multi-state or Integrated(Ext + Research)


Funding Source



Corn yield forecasts, Corn yield estimates


Page last updated: July 21, 2011
Page maintained by Julie Honeick,