Extreme Weather Produces Bad Results in Corn and Soybeans

August 29, 2011

 

Lower Corn and Soybean Yields in Pro Farmer Tour

 

Pro Farmer yield estimates in corn and soybeans are down sharply from normal in the key Midwest growing areas, due to drought and heat stress.  The projected corn yield at 147.9 bushels per acre would be much worse than the USDA August 1 estimate 153 bushels per acre.   

 

Indeed, the new-crop yield would be the lowest since 2002 as a percent below trend, down 7.2%.   The trend yield  represents the expected yield with normal weather and continues to rise, over time, due to improvements in technology.

 

 

The hottest July temperatures since 1955 occurred in Midwest corn.   For the month, Corn Belt temperatures were 4.1 F above the 1950-2010 mean value.   Above normal temperatures in the hottest month of the year are very damaging for corn in the sensitive pollination stage.   Yield losses are irreversible since kernels not successfully pollinated will never develop into grain.
 

 

Why Normal Weather is Best

 

The reason corn is successfully grown in the Midwest is because the climate and soil conditions are favorable for corn.   Florida farmers do not grow corn because the climate is too hot.   By the same token, oranges could not be produced in Iowa because of a short growing season and freezing temperatures.   The main point is this, if growing conditions stray too far from normal there is a penalty to pay in a reduced yield.

 

The hottest July in 55 years is a really big deal, suggesting further losses in corn may still be coming as the harvest advances and poor yields are revealed.

 

Soybean Yields May Be Overstated

 

Pro Farmer soybean yields were pegged at 41.8 bushels per acres.   This would be 3% below the United States  2011 trend-line  yield.   The sampling method used by the tour measured the number of pods in a 3 x 3 foot square area.    

 

The size of the soybeans in the pod was not taken into account.        This is important because if pod-filling conditions are too dry,   tiny BB-sized beans would result, further depressing the yield.

 

 

Very low August rainfall has occurred in Iowa, Illinois and Minnesota,  the 3 states that last season grew 45% United States soybeans.    The Pro Farmer 3-state yield estimates, as a weighted average, was 50.6 bushels per acre compared to 47.2 bushels per acre in the USDA August 1 report.

Soybean conditions worsened in August.   Between July 31 and August 21, soybeans fell to 62% good-excellent, and down 6% in the 3 states.   Poor-very poor soybeans gained 4%, increasing to 11% .

 

For a look at very dry August growing conditions in the 3 states, see the August 1-28 rainfall below.       Not much moisture is expected this week to close out the month.   

 

Pro Farmer Tour Good Proxy 

 

The Pro Farmer Tour took samples of corn and soybeans in the top Midwest states for corn and soybeans, and thus was not a national referendum on crop conditions.   Even so, the states covered in the tour make up more than 85% of US corn and soybeans and produce the highest yields.    See where corn and soybeans are grown below: