Following USDA's National Agricultural Statistics Service release of the 2011 Crop Acreage Report on June 30, three big questions remain.

1)      How accurate is this report?

2)      How many acres will be lost to flooding?

3)      What will be the final 2011 crop yield?

Iowa State University Extension farm management specialist Steve Johnson provides the following observations and information to help answer those questions, which are important as you plan your corn marketing strategy.

"As corn is moving into the critical pollination period here in the last half of July, a heat wave has hit the crop in Iowa and pretty much the entire Western Corn Belt," he notes. "Granted, farmers planted a big U.S. corn acreage this year, but yield will be the key in determining the final corn production number. Keep an eye on the situation and watch for the updated yield estimate for the U.S. and for key corn growing states in USDA's August Crop Report, which will be released on August 11."

How accurate is USDA's annual June 30 Acreage Report?

NASS uses an area frame survey methodology that includes over 11,000 frames or roughly 1 mile by 1 mile sections across major corn and soybean producing states. NASS over-samples larger producing states and the more productive land in those states. Because NASS returns annually to approximately 80% of these frames, the change in crop rotations is easier to determine. That data was gathered from May 27 until June 15, 2011.

This method is statically sound and NASS has indicated that they plan to resurvey the acreage in four states this summer: Minnesota, South Dakota, North Dakota and Montana and results will be included in the USDA's August Crop Report, which will be released August 11.

The relative standard errors from the 2011 area frame survey for the U.S. are 1.1% for corn and 1.2% for soybeans. Statistically, the June 30 Acreage Report could be above or below the 92.3 million acres planted to corn by about 1 million acres. For soybeans, use of the 2011 area frame survey methodology has a relative standard error of 1.2%. This final number could vary by about 900,000 acres nationwide either higher or lower than the 75.2 million acres reported on June 30.

Comparing planted corn acres vs. harvested corn acres

While much attention was given to the planted acreage numbers, it's actually the harvested acres for grain that is used to determine the final corn production numbers that will be released by USDA in early January 2012.

Over the past few years, approximately 91.9% of the nation's acres planted to corn are harvested for grain. The balance of the 8.1% of U.S. corn acres not harvested is seed corn, food-grade corn, silage and acres lost due to weather or flooding. Because of higher corn prices in 2011, some pre-season estimates were that this percent could exceed 92%. However, delayed planting and flooding along major rivers puts this expectation into question.

In the July 12 USDA Crop Production Report, the World Agricultural Supply and Demand Estimates (WASDE) report used 92% of the 92.3 million corn-planted acres or 84.9 million harvested acres. Lowering harvested acres by .1% to .2% means an additional 80,000 to 160,000 acres that were planted but not harvested.

U.S.                  Harvested               Harvested     Harvested

Corn                   @ 92%                   @91.9%           @91.8%

Planted 
Acres                                                                                       _______

92.3 M   84.9 M                    84.82 M     84.73 M

STEVEN D. JOHNSON, Ph.D.

However, private estimates by Lanworth, Inc., a firm that uses field and low-level satellite observations indicated that as of late June approximately 460,000 acres of corn along the Missouri River were planted but will not be harvested. Their soybean acreage projection was estimated at 360,000 acres. Flooding concerns along the Ohio and Mississippi Rivers would be much lower than the Missouri River, and many of these acres were replanted as the flooding occurred in April and May.

Comparing corn harvested acres and corn yield per acre

While both planted and harvested acres are important, a change of 1% in U.S. planted corn acres equals about a 2 bushels per acre yield change in determining final corn production numbers. Using the bar graph below, the first bar shows how many bushels are lost or gained by 1 million corn-planted acres or about 157 million bushels.

The balance of the bars on the graph indicates various corn yield deviations. In the past five years, the U.S. has seen a yield variance of 15.6 bushels per acre, ranging from a low of 149.1 bushels per acre to 164.7 bushels per acre. This is a net variance of 1.42 billion bushels on 91 million planted corn acres.

Conclusion: Yield is a much bigger factor than acres

Yield is a far bigger factor in determining final U.S. corn production than are planted or harvested acres.

U.S. trendline yields over the past five years are roughly 163 bushels per acre. However, the USDA World Agricultural Outlook Board lowered their 2011 corn crop yield forecast to 158.7 bushels per acre in their Crop Production Report released May 11, 2011. This number was reduced as a result of late planting and wet spring growing conditions in many parts of the Corn Belt.

However, USDA is yet to compile actual yield estimates for spring planted crops. This yield information for corn will be collected by NASS using two different survey methods. The first is an agricultural yield survey for all states. It has a sample size of approximately 28,000 farms nationwide and 800 farms in Iowa. The sample is drawn randomly of farmers nationwide that are known to produce the particular crop being surveyed.

Circle the date August 11 on your calendar

NASS also conducts an objective yield survey which tends to be the first in-field yield estimate for spring seeded crops. Field measurements are taken on over 1,900 corn samples and 1,800 soybean samples nationwide in late July and early August.

These fields as well as the specific locations within the field are drawn randomly from the major corn and soybean producing states. The results of both of these NASS survey methods will be compiled and released on August 11, 2011.

The USDA's World Agricultural Outlook Board will then adopt the NASS acreage and yield estimates and release their August Crop Production Report that includes both supply and demand figures. Regardless of the results that are released on August 11, the certainty of U.S. crop production will not be known until early January 2012. That's when the final crop production numbers are released by USDA.

For farm management information and analysis, go to ISU's Ag Decision Maker site www.extension.iastate.edu/agdm and ISU Extension farm management specialist Steve Johnson's site www.extension.iastate.edu/polk/farmmanagement.htm.