More research on corn sweats

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My blog post on “corn sweats” was widely read and got reprinted in some publications. In fact, it was read by an author of one of the articles I used as a reference. 

Dr. Satish Gupta, emeritus professor at University of Minnesota, sent an email with some concerns about some of the wording used in the post and with findings from a separate study. 

From Dr. Gupta:

"The part I am concerned about is the following text where '...corn may have much higher evapotranspiration....'

FROM THE BLOG: "Recent studies showed the amount of evapotranspiration between cornfields and prairie habitats are fairly similar in eastern area of the Corn Belt, but corn may have much higher evapotranspiration in dryer areas, such as the Great Plains."

"As we stated in the Abstract, even if we count ET (evapotranspiration) from 1 May, prairie ET was similar or slightly higher than corn. However, if we go back to the 1850s when immigrants came here and all land was under prairies, natural and man made fires were quite common. Thus combined ET from previously burned and recently burned prairies in landscape will be less than ET from corn and soybeans. Around 1910, ET will be less from the landscape than now and it is mainly because we grew small grains which use less water. Basically, a drier climate dictated what the immigrants could grow (small grains) at that time. Since we are getting more rain now and varieties are better, soybean production has replaced small grain production.

"The other text I am concerned about is that '... much of the observed rainfall increase ... is attributable to agricultural intensification in the central United States.'

"This conclusion goes against water balance. Excess water leaves the landscape as a river discharge. If the same water from land (ET) keeps on recycling and shows up as excess rainfall, our river discharges will be the same (from year to year) but that is not the case. I am attaching two papers that show that our PPT is increasing and so are our river flows. This means, the increase in PPT in the central US is NOT due to corn ET but extra PPT brought mainly from the Gulf of Mexico. However, some of the corn ET does come down as PPT but that applies to any vegetation that grows in the landscape. If prairie or trees were growing in the landscape, some of their ET will also come down as PPT.

FROM THE BLOG: "One study says yes. According to an article in Geophysical Research Letters, results of both regional climate model simulations and observational analyses suggest that much of the observed rainfall increase - as well as the decrease in temperature and increase in humidity - is attributable to agricultural intensification in the central United States."

This a good example of why scientific studies should be acknowledged as being rigorously reviewed and is not just automatically accepted by the community as a whole.  While some issues may be debated, differences are based on strict scientific principles.

For the next blog post, I’ll be discussing the recent supercell and tornado outbreak in early August for Northern Illinois.