istorical
grain yields provide us with a glimpse of yields yet to come, although like
the stock markets, past performance is no guarantee of the future. State average
corn grain yields in Indiana have increased at a fairly constant 1.6 bushels
per acre per year since 1930 primarily due to improved genetics and production
technology (Fig. 1). Some question whether the straight line relationship
For the past ten years, Indiana's corn crop yield has split about even, with four of those years below trend and six above. The final USDA estimate for 2005 puts the Indiana corn crop at 154 bushels per acre (bpa), or nearly 5 percent above the 2005 trend line yield of 146.9 bpa but about 8 percent below last year's record crop of 168 bpa (Fig 1). By comparison, recent years' departures from trend yield (Fig. 2) were 2004 (+15.7%), 2003 (+1.7%), 2002 (-14.8 %), 2001 (+11.2 %), and 2000 (+6.0 %). Final 2005 corn production estimates (Jan 2006) for each county in Indiana are available in text or graphical formats.
Fig. 1
Fig. 2
Annual grain yield values fluctuate above and below the trend line throughout the more than 70 year period of records, but four weather-related disaster years are especially noteworthy. Late planting plus early fall frosts in 1974 decreased state average corn yields 26% below the trend value for that year. Severe droughts in 1983, 1988 and 1991 resulted in yields 34%, 30% and 26% less than their respective trend values.
Because the departures from trend for these four years are so dramatic, it is of some interest to calculate the trend line for corn grain yield without their inclusion. In so doing, the annual rate of yield increase is slightly greater (1.7 versus 1.6 bu/ac/yr) and the estimated trend yield for 2006 changes from 148.5 to 152.8 bpa (Fig. 3). Such values may be more true estimates of statewide yield potential in "normal" years.
Fig. 3
The top five U.S. corn grain producing states are Iowa, Illinois, Nebraska, Indiana and Minnesota (Fig. 4). According to the final USDA production estimates for 2005 (published Jan 2006), these five states (7.2 billion bushels) accounted for about 65 % of the total estimated grain yield for the U.S. in 2005 (11.1 billion bushels).
Fig. 4
For the first time in a number of years, corn yields per acre in 2004 for the U.S. Midwest rivaled those often obtained in more western areas of the U.S. (Fig. 5). Consistently high corn yields are more often achieved in western states such as Washington and Arizona because of their relatively better corn growing climates including a) fewer cloudy and hazy days, b) less rainfall and humidity contributing to less disease, c) availability of irrigation, and d) fewer stressful hot nights during grainfill.
Fig. 5
For more statistics about Indiana agricultural production, browse the Web site of the Indiana Agricultural Statistics Service at http://www.nass.usda.gov/in/.
For more statistics on U.S. national crop production estimates, look at the National Agricultural Statistics Service Crop Production Web site.
USDA-NASS. Jan 2005. Crop Production 2004 Summary. United States Dept. of Agr - Nat'l Ag. Statistics Service, Washington, D.C. Online at http://usda.mannlib.cornell.edu/reports/nassr/field/pcp-bban/cropan05.pdf [URL verified 8/9/05].
