As of May 12, 15 percent of Iowa’s corn was planted (USDA-NASS).  This is a slower pace than what Iowan’s experienced even in the flood year, 1993, when 20 percent was planted at this time in May. The 8 percent planted before May 5 was subjected to dramatic soil temperature changes as well as up to a foot of snow in parts of Iowa. Many Integrated  Crop Management News articles, blogs, Twitter posts, and other media document  spring 2013 conditions and concerns

Elmore, Roger W.

Taylor, S. Elwynn

English

As of May 12, 15 percent of Iowa’s corn was planted (USDA-NASS).  This is a slower pace than what Iowan’s experienced even in the flood year, 1993, when 20 percent was planted at this time in May. The 8 percent planted before May 5 was subjected to dramatic soil temperature changes as well as up to a foot of snow in parts of Iowa. Many Integrated  Crop Management News articles, blogs, Twitter posts, and other media document  spring 2013 conditions and concerns.</p

Elmore, Roger

Digital Repository @ Iowa State University (ISU)

4/13/2014 weather forecasting and correlating corn planting dates with yieldhttp://www.extension.iastate.edu/CropNews/2013/0515elmoretaylor.htm 1/4PRINT STORYEMAIL STORYADD TO DELICIOUS ATOM FEEDFOLLOW ON TWITTER Subscribe to CropNewsArchives2014201320122011201020092008 Previous YearsISU Crop ResourcesExtension FieldAgronomistsCrop & Soils InfoPesticide ApplicatorTrainingAgronomy ExtensionEntomology ExtensionPlant PathologyExtensionAg and BiosystemsEngineering ExtensionAgribusinessEducation ProgramIowa Grain QualityInitiativeCollege of Agricultureand Life SciencesISU ExtensionAnalog Years for Weather Forecastingand Correlating Corn Planting Dates withYield in IowaBy Roger Elmore and Elwynn Taylor, Department of AgronomyAs of May 12, 15 percent of Iowa’s corn was planted (USDA-NASS).  This is aslower pace than what Iowan’s experienced even in the flood year, 1993,when 20 percent was planted at this time in May. The 8 percent plantedbefore May 5 was subjected to dramatic soil temperature changes as well asup to a foot of snow in parts of Iowa. Many Integrated  Crop ManagementNews articles, blogs, Twitter posts, and other media document  spring 2013conditions and concerns. To the surprise of many, soil moisture profiles across the state are filled orclosely filled as we write. The U.S. Drought Monitor receded to the west andnorthwest every progressive week. Based on what has already happened,what does the 2013 cropping season look like from this mid-Mayperspective? Analog: A person or thing seen as comparable toanotherWhen faced with different weather patterns like those we’ve experienced sofar this year, we often turn to analog years. These are years considered ashaving similar trends in temperature and/or precipitation as those we arecurrently experiencing.  Whether we agree or not, people use analog years tocompare data like planting progress as well. It is often tempting to speculatethat if we’ve had similar trends in weather or planting dates historically, wecan use that as an analog year to forecast conditions – and thus corn yields -the rest of the current growing season.  Even if the analog year is not a totallyreliable for the yield outlook it does at least provide an idea of the risks andpotentials that could be experienced during the growing season. Spring weather analog year for 2013: 1947Figure 1 displays Iowa state average Growing Degree Day(GDD)accumulations, Precipitation, and Stress Degree Days (SDD) for April1 through May 8 for 1947, 1995 and 2013. 1947 is suggested as a spring-weather analog year for 2013. This is probably based on certain similaritiesof April weather in both years. April through June 1947 was cold and wet.Corn stands were reduced by ‘water damage’ across the state. The cold-wetweather transitioned to drought in July (Figure 2).  By July 20th, 1947, heatstress set in and GDD exceeded normal (Figure 2). ICM Home ISU Extension Calendar Publications Extension News County Offices Contact Us4/13/2014 weather forecasting and correlating corn planting dates with yieldhttp://www.extension.iastate.edu/CropNews/2013/0515elmoretaylor.htm 2/4Figure 1.  Iowa Average Accumulated Growing Degree Days (GDD),Precipitation, and Stress Degree Days (SDD) for Spring 1947, 1995  and2013. Graphs from Mesonet. Full-size image4/13/2014 weather forecasting and correlating corn planting dates with yieldhttp://www.extension.iastate.edu/CropNews/2013/0515elmoretaylor.htm 3/4Figure 2. Iowa Average Accumulated Growing Degree Days (GDD),Precipitation, and Stress Degree Days (SDD) for the 1947, 1995 and 2012Growing Seasons. Graphs from Mesonet. Full-size image Planting dates in 1947 ranged from May 5 to May 21 (Elmore unpublisheddata). About half of the 1947 corn crop was planted by May 15. This mayseem late to us now, but this range of planting dates and the 50percent planted date were normal for that era.  However, early rains probablyresulted in shallow rooting. This coupled with stress later in the 1947growing season probably reduced corn yield (Figure 2). Mid-season heatcoupled with limited rain reduced Iowa average corn yields to 31 bushels peracre, 39 percent below the 1937-2012 trendline yield (Figure 3). Figure 3.  Corn yield United States. and Iowa, 1866-2012. Data from USDA-NASS. Full-size image Corn planting date analog years for 2013: 1984,1993 and 1995Another way to think about analog years is planting progress. As mentionedin our introduction, as of Sunday, May 12, only 15 percent of Iowa’s corn wasplanted. That was an increase from 8 percent the week before. Little cornplanting occurred May 6–10 because of mid-week rains that unfortunately re-saturated fields just when they were nearly dry enough for planting followingthe early May snow; this delayed planting once more.  Since 1980, planting progress in early May of three years - 1984, 1993 and1995 - was similar to what we’ve experienced this year.  Because floodingresulted in delayed planting in 1993, let’s focus on the other two as possibleanalog years for planting date. 1984: Six percent of Iowa’s corn was planted by May 6; however, one weeklater, by May 13, Iowa farmers planted another 29 percent (Figure 4). Plantingin 1984 began by April 29 and ended by June 10. Half the crop was plantedby May 15, 1o days behind the 1978-1987 average of May 5 (Elmore, 2013, inpress). By May 12 of this year, 2013, we only had 15 percent of our cornplanted for the reasons we mentioned above.  Corn yields in 1984 were 3percent above trend line (see Pierson & Elmore) (Figure 3).  The delayedplanting in early May was correlated with increased yields. Although 1984SDD were slightly greater than normal, there were fewer SDD in that yearcompared to either 1947 or 1995.4/13/2014 weather forecasting and correlating corn planting dates with yieldhttp://www.extension.iastate.edu/CropNews/2013/0515elmoretaylor.htm 4/4Copyright ©2014 Iowa State University Extension | Iowa State UniversityContact us | For Staff | Nondiscrimination and Information Disclosures | CMS AdminLast Updated 5/16/2013Figure 4.  Percent of Iowa's corn planted at different dates and years. 2004 and 2009 yields were well-above trend line. Record breaking plantingprogress occurred in  2010. Adapted from USDA-NASS data. Full-sizeimage 1995: Only 10 percent of Iowa’s corn was planted by May 7, 1995 (Figure 4).Another 20 percent was added the next week and 62 pecent of the crop wasin by May 21.  Although planting progress was similar to that of 1984, yieldsin 1995 were 9 percent below trend line (see Pierson & Elmore) (Figure 3).Planting delays in 1995 were correlated with reduced yields; please note thisdoesn’t mean delays that year actually reduced yields. The primary impact in1995 was high heat stress following silking relative to normal (Figure 2). CautionsAlthough analog years for weather and corn planting dates are interestingand help us understand potential hazards as well as opportunities, they mayor not be accurate predictors of what will happen in 2013. Weather patternsthe rest of the growing season will dictate that. Roger Elmore is a professor of agronomy with research and extensionresponsib ilities in corn production. He can be contacted by email atrelmore@iastate.edu or (515) 294-6655. Elwynn Taylor is extensionclimatologist and can be reached at setaylor@iastate.edu or by calling (515)294-1923. This article was published originally  on 5/15/2013 The inf ormation contained within the article may  ormay  not be up to date depending on when y ou are accessing the inf ormation.Links to this material are strongly  encouraged. This article may  be republished without f urtherpermission if  it is published as written and includes credit to the author, Integrated CropManagement News and Iowa State Univ ersity  Extension. Prior permission f rom the author isrequired if  this article is republished in any  other manner.

Analog Years for Weather Forecasting and Correlating Corn Planting Dates with Yield in Iowa

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1082&amp;context=cropnews

Analog Years for Weather Forecasting and Correlating Corn Planting Dates with Yield in Iowa

Abstract

Similar works

Full text

Available Versions

Digital Repository @ Iowa State University (ISU)