Based on conditions here in early August, Iowa looks like it's heading for a high corn yield this year—maybe even a new state record.
Iowa's average corn yield in 2004 was 181 bushels per acre, the highest ever recorded. "Our assessment of current crop conditions and weather reports indicates that the 2009 corn yield can possibly be every bit as high," says Elwynn Taylor, Iowa State University Extension climatologist. Taylor, along with ISU Extension corn agronomist Roger Elmore, have analyzed the 2009 situation and are using a computer model to compare it to years past when yields were high.
Cool nights help boost corn yields in Iowa
Historical data (since 1952) show that late planting reduces crop yield potential but cooler than usual temperatures from planting to silking have little definitive impact on final yields at harvest. On the other hand, temperature from silking to R6, the blacklayer stage, has a major impact. Higher than usual daytime – and nighttime – temperatures often bring on water stress and reduced yields (e.g. 1988). Warm night-time temperature even when day-time heat is not excessive tends to reduce yield by shortening the filling period. Cool night-time temperatures after silking are associated with the higher yielding years in Iowa.
Based on years with similar conditions through July as we have had this year, the chance of continued cool weather is more likely than a change to hotter than usual, says Taylor.
Real chance of having corn yields as good as 2008
The weather and corn yield estimation model "Hybrid-Maize" shows a strong relationship between night-time temperature and relative yield (see figure below - the model allows for comparisons over years with weather as the only variable). Much of the modeled impact on yield was related to cooler temperatures causing an extending of the period from silking to R6. Note: although the model shows a possible yield of 280 bushels per acre this should be shifted to the reality of 2008 when the yield was 171 bushels (not 280 bushels per acre). The model assumes all factors other than weather are perfect.
Taylor and Elmore's assessment is: the chance of having corn yields as good as 2008 is very real for Iowa this year.
Predicted Yield and Average Minimum Temperature
Ames, IA. - Negatively related, R = -0.53
* Yields predicted using Hybrid-Maize,
Ames IA, 1986 -2008
USDA likely to raise crop production estimates
A survey in late July and early August by Farm Futures magazine shows good yield prospects as the unusual 2009 growing season continues. Bumper corn and soybean crops are still possible in 2009, despite a very unusual growing season, according to this latest Farm Futures survey of U.S. farmers.
Corn production could reach 12.545 billion bushels, the second biggest U.S. crop in history, with soybeans setting an all-time high at 3.275 billion bushels.
USDA will report the first official estimate of 2009 production for corn and soybeans on Aug. 12, when it releases its August Crop Production Report. This is a widely anticipated release that features the agency's first yield estimates based on in-field surveys, not statistical guesses. The government also will update acreage for corn in seven states with a special survey in the eastern Corn Belt, where planting delays made the estimates in USDA's June 30, 2009, Planted Acreage Report uncertain.
Corn acres may be less, but yields may be more
Farm Futures conducted its survey of farmers July 24 to August 5. Farm Futures found a 2 million acre drop in corn plantings from USDA's June survey, with the total falling to 85.04 million planted corn acres in 2009. But the farmers also reported expectations of above average yields of 160.3 bushels per acre this year, compared to the current USDA statistical guess of 153.4 bushels per acre. Farm Futures production estimate is 255 million bushels above the July government forecast for corn in 2009.
Farm Futures survey puts the average U.S. soybean yield at 42.8 bushels per acre for 2009, slightly higher than USDA' s trend forecast. But any corn or soybean production estimates made now come with a big asterisk. Weather during the rest of the 2009 growing season will determine final yields, and the delayed maturity of both crops leaves them vulnerable to frost. Damage from early cold happens rarely, but when it does--such as the early fall frost that occurred in the U.S. Corn Belt in 1974 and 1993 – the impact can be huge.