Fundamentally Speaking

Summer Temps Effect on Corn Yields

Grain and oilseed futures have recently responded to some bullish news including August crop production less than expected, figures from the Farm Services Agency implying less planted acreage than currently projected, and continued dryness in up to 35% of the Corn Belt exacerbated this week by the return of above average temperatures.

Of these, weather may be the most important as yield changes for both corn and beans often have a far greater impact on final production than any acreage revisions.

In many key areas, rains have been well below average for the past six weeks to the detriment of corn, which needs another one of two good rains to finish out what should be a respectable year.

For soybeans, the need for precipitation is more urgent given the crop is in the midst of its’ critical pod setting and filling stage.

One of the key question’s being asked is how much good subsoil moisture from heavy spring rains and cooler than normal temperatures over past month has helped offset the negative impact from dry conditions over same 30 day period.

P[L1] D[0x0] M[300x250] OOP[F] ADUNIT[] T[]

This graph shows the percent final corn yields deviated from the 25-year trend vs. the departure of average July-August temperatures from the 1986-2011 average.

The data is for the East North Central region of the country, one of the geographical regions compiled by NOAA for weather data purposes.

This region of the country is 22.1% Iowa, 22.9% Michigan, 33.0% Minnesota, and 22.0% Wisconsin.

A weighted average of these states corn production based on these percentages along with the weighted average of harvested acreage were used to generate a corn yield for this East North Central region of the country.

A trend-line was used to calculate the percent that each year’s corn yield deviated from this trend.

These deviations were compared to the number of degrees that the average July-August temperatures differed from the 1986-2011 July-August average that is 69.1 degrees.

The chart shows that since 1986 there have been 11 years when the July-August average temperature was below 69.1 degrees and all but two of those years, 1993 and 1996, had trend or higher corn yields for this part of the country.

On the other hand, there were 16 years when temperatures were above average and seven of those years saw yields below trend.

Of course, precipitation does matter and within the boxes for each year is the percent of summer (June-August) precipitation for this region of the country compared to the 1986-2011 average and that is 11.8 inches.

For instance, last year corn yields in the East North Central region of the country were 14.3% below trend and while that is better than the U.S. as a whole where 2012 yields were 23.8% below trend it is the worst for this area of the country since 1988.

Reasons for this poor performance include that July-August 2012 temperatures were 2.5 degrees above average and June-August 2012 precipitation was only 76% of average.

We note that even with cool temperatures 1993 yields were 34.9% below trend as precipitation that summer was 150% of average.

The only other year seeing summer precipitation this heavy was in 2010 but the copious moisture must have helped with yields that year 1.6% above trend despite July-August temperatures 2.7 degrees above average.

(KA)

P[] D[728x170] M[320x75] OOP[F] ADUNIT[] T[]
P[L2] D[728x90] M[320x50] OOP[F] ADUNIT[] T[]

Comments

To comment, please Log In or Join our Community .