Climate Change: Effect of 1922-2002 Weather on Corn Yield for a Transect from Raymondville, TX, to Brookings, SD

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E. C. A. Runge, Professor and Billie Turner Chair in Production Agronomy (Emeritus), Soil & Crop Sciences Department, Texas A&M University, College Station 77843-2474; and John F. Benci, Consultant, 382 Moore Road, West St. Paul, Manitoba, Canada R4A 7A2

Abstract

The western Corn Belt and southwestern corn growing areas have highly variable year-to-year corn yields due to variation in rainfall and variation in frequency of high temperatures during the growing season. Irrigation is practiced at many locations to stabilize year-to-year yield variation. Early planting is desirable since higher temperatures coupled with less rainfall occur more frequently as the growing season or year advances. In this study weather records were used simulate corn yields for the period 1922-1997 or 1922-2002. Western and southwestern corn growing locations were selected from Raymondville, TX, to Brookings, SD, on a 1250-mile-long transect. Model results indicate that weather associated with early tassel dates always produced the best yield for all locations. Yield simulations were made for three plant-available stored soil moisture levels at or near planting time. Weather data were selected to have corn tassel from 22 April to 3 June for Raymondville and ranged from 24 June to 5 August for Manhattan, KS; Lincoln, NE; and Brookings, SD, locations to produce early, early to normal, normal to late and late tassel dates for all 12 locations. Model results agree with observations that early planting, and large amounts of plant-available stored soil moisture at planting time are essential to achieve desired corn yields at these locations under non-irrigated conditions.

Introduction

The study utilized the water balance model (5) derived from plot data from the 1969, 1970, and 1971 growing seasons from four sites along a 200 mile north-south transect in Illinois (4). Farmer’s fields were selected where soil variation caused large differences in plant-available stored soil moisture within small areas (4,6). All plots at a location were within 2 acres and were within larger fields. Rainfall and temperature data collected on site represented each location. Rainfall and temperature differences occurred between years at each site and between sites within and between years (4). Plant available stored soil moisture differences occurred due to variation in thickness of loess overlying high bulk density glacial till (LaSalle and Champaign counties), and due to variation in depth to horizons high in Na⁺ concentration [Fayette Co., two locations (4)]. Both soil conditions restrict rooting depth and limit plant-available stored soil moisture depending on the thickness of the root zone. The model explained 81% (R²) of the corn yield variation for these four sites for these 3 years [see (4,5) for additional detail].

Locations of the 12 sites along the transect are given in Figure 1. In addition to the results from this study others have also documented the rapid reduction in corn yield as planting and tasseling are delayed (7). The decision facing corn growers is one of trading frost risk due to early planting for drought risk when planting is delayed (7). The water balance model (5) uses readily-available data and can be applied to any location where rainfall and maximum daily air temperature records are available. The ready availability of data to drive the model (5) is in contrast to data requirements of other models (1,2).

Fig. 1. North-south transect from Brookings, SD, to Raymondville, TX.

Concern and Limitations

One concern with using the model (5) that must be answered is how technology used to produce corn in 1969-1971 in Illinois compares to technology currently used to produce corn at these 12 locations. In a prior study (8) experimental technology (4) was related to Corn-Belt technology for the years 1968-1972. The state average corn yields from www.nass.usda.gov were divided by simulated yields for 1968-1972 and multiplied by 100 to give percentage. The average was 65.2% (8). Average technology used in growing corn today is above what was practiced when the model was derived (11). DeKalb’s XL 45 and XL 45a hybrids were used (4) and these hybrids were among the first widely adapted high population single cross hybrids grown. Average plant population in the study (4) was 21,425 plants per acre and ranged from 18,225 to 25,717. The average plant population for Illinois, Indiana, and Iowa in 1969-1971 was 17,800 while it was 27,400 plants per acre for 2004-2006 (Ty Kalaus, Field Crop Section, NASS-USDA, personal communication). Much of the increase in corn yield since 1969-1971 is due to higher plant population (3). The length of the weather record varies from 1922-1997 for some locations and from 1922-2002 for others. Weather records had missing data for some years for some locations. When data are missing no yield appears for those years (i.e., Figs. 2 to 13).

Fig. 2. Simulated corn yields for Raymondville, TX, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (2a) 22 April tasseling date; (2b) 6 May tasseling date; (2c) 30 May tasseling date; (2d) 3 June tasseling date.

Fig. 3. Simulated corn yields for Beeville, TX, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (3a) 22 April tasseling date; (3b) 6 May tasseling date; (3c) 30 May tasseling date; (3d) 3 June tasseling date.

Fig. 4. Simulated corn yields for Brenham, TX, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (4a) 22 April tasseling date; (4b) 6 May tasseling date; (4c) 30 May tasseling date; (4d) 3 June tasseling date.

Fig. 5. Simulated corn yields for College Station, TX, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (5a) 22 April tasseling date; (5b) 6 May tasseling date; (5c) 30 May tasseling date; (5d) 3 June tasseling date.

Fig. 6. Simulated corn yields for Hillsboro, TX, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (6a) 6 May tasseling date; (6b) 20 May tasseling date; (6c) 3 June tasseling date; (6d) 17 June tasseling date.

Fig. 7. Simulated corn yields for Kaufman, TX, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (7a) 6 May tasseling date; (7b) 20 May tasseling date; (7c) 3 June tasseling date; (7d) 17 June tasseling date.

Fig. 8. Simulated corn yields for Sherman, TX, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (8a) 6 May tasseling date; (8b) 20 May tasseling date; (8c) 3 June tasseling date; (8d) 17 June tasseling date.

Fig. 9. Simulated corn yields for Stillwater, OK, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (9a) 27 May tasseling date; (9b) 10 June tasseling date; (9c) 22 June tasseling date; (9d) 8 July tasseling date.

Fig. 10. Simulated corn yields for Ottawa, KS, for weather from 1922-1997, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (10a) 10 June tasseling date; (10b) 24 June tasseling date; (10c) 8 July tasseling date; (10d) 22 July tasseling date.

Fig. 11. Simulated corn yields for Manhattan, KS, for weather from 1922-2002, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (11a) 24 June tasseling date;(11b) 8 July tasseling date; (11c) 22 July tasseling date; (11d) 8 August tasseling date.

Fig. 12. Simulated corn yields for Lincoln, NE, for weather from 1922-2002, for four tasseling dates, and for three plant-available stored soil moisture levels at planting. (12a) 24 June tasseling date; (12b) 8 July tasseling date; (12c) 22 July tasseling date; (12d) 8 August tasseling date.

Fig. 13. Simulated corn yields for Brookings, SD, for weather from 1922-2002, for four tasseling dates, and for three plant-available stored soil moisture levels at planting time. (13a) 24 June tasseling date; (13b) 8 July tasseling date; (13c) 22 July tasseling date; (13d) 8 August tasseling date.

A second concern is whether or not the results from this (4) study represent growing conditions for locations used in this study. DeKalb’s XL 45 and 45a hybrids were grown over a very large geographic area and hybrids used at transect locations selected have maturity dates similar to DeKalb’s XL 45 and XL 45a. Some rainfall and temperature data for some locations may be outside the data set used to develop the model, however for the most part weather records for developing the model and for transect locations are similar. Therefore, yield simulations reported here should characterize the impact weather has had on corn yields for transect locations over the past 75 to 80 years. The model is sensitive to high maximum temperatures and low amounts of rainfall, in particular, so yields for early tassel dates are higher and more consistent than they are for later tassel dates for all locations except for Brookings, SD (Figs. 2 to 13). Yield simulations and year-to-year variation agree with corn production and yield history (7) for the College Station location. Results also agree with experience and mimic NASS reported yields (www.nass.usda.gov).

Data Presented

Simulated corn yields are used to demonstrate results for each transect location (Figs. 2 to 13). Results indicate what the expected corn yield would be for each location for any previous year if that weather reoccurred and if corn was grown as it was from 1969-1971 for 4, 7, and 10 inches of plant-available store soil moisture at planting time (4). Results are reported in bu/acre for all locations (Figs. 2 to 13). No yield is reported for any year when weather data are missing.

Yields reported were determined by the model and have not been adjusted for any improvement in technology that occurred since 1969-1971. An upward adjustment in yield may be necessary to arrive at yields using today’s technology when compared to county yields reported by NASS-USDA. Results in a subsequent paper (10) suggest that the model captures the upward bias in yields that occur when weather is favorable [i.e., 2004 Corn-Belt yields (10)]. However the model may not capture the increase in corn yields when moisture is more limiting [i.e., 2005 corn belt yields (10)]. If that is true, then current hybrids are more drought tolerant than were DeKalb’s XL 45 and 45a hybrids.

Yields

All locations. Several aspect of the results are consistent for all locations. The importance of large amounts of plant-available stored soil moisture at planting time (10 inches) is necessary to have good corn yield prospects for weather for all locations and years (Figs. 2 to 13). As tasseling dates are delayed corn yields are reduced dramatically (Figs. 2 to 12) for all years and for all plant-available stored soil moisture levels at planting time (7). Brookings, SD, is the only location where yields are not reduced as tasseling date is delayed (Fig. 13).

Raymondville, TX. Yield simulations for Raymondville are the lowest for any location on the transect (Fig. 2). Yields with 4 and 7 inches of plant available stored soil moisture at planting time are very low and many years have zero yields Weather over 75 years for growing corn has not changed from 1922-1997. Model results confirm that acceptable corn yields only occur when corn is irrigated at Raymondville.

Beeville, Hillsboro, and Sherman, TX; Stillwater, OK; and Lincoln, NE. Results are presented in Figures 3, 6, 8, 9, and 12 for these locations, respectively. Yields have a slight positive slope for these locations indicating that weather over the past 75 or 80 years has become somewhat more favorable for growing corn. The positive trend is small but is otherwise similar to results for Brenham, College Station, and Kaufman, TX; and Ottawa and Manhattan, KS, locations. Yields decrease quickly as tasseling moves to later dates. Low and zero corn yields are frequent for soils with 4 inches of plant-available stored soil moisture at planting time and for late tassel dates. Planting early, to achieve an early tassel date, is important to achieve high yields in most years at these locations (7). Corn growers face the decision of planting early and incurring a frost risk versus planting later and incurring a drought risk.

Brenham, College Station, and Kaufman, TX; and Ottawa and Manhattan, KS. Results are presented in Figure 4, 5, 7, 10 and 11, respectively. Yields have not changed due to weather over the past 75 or 80 years. Otherwise results are similar to Beeville, Hillsboro, and Sherman, TX; Stillwater, OK; and Lincoln, NE, locations. Planting early is important to achieve high yields as yields decrease quickly as tassel date moves to later dates (7). Zero yields are common for 4 inches of plant-available stored soil moisture at planting time and increase in frequency as tasseling date is delayed.

Brookings, SD. Brookings, SD, has by far the largest increase in corn yield due to improved weather for the past 80 year period for any of the 12 locations studied. Later planting and lower amounts of plant-available stored soil moisture at planting time at Brookings still produce high corn yields compared to the other 11 locations studied. Yields are higher and year-to-year yield variation is lower for Brookings than for any other location. Also yields do not decrease as tasseling is delayed as it does for the other 11 locations studied.

Conclusions

Model simulated yields are a good indication of what corn yields would be today if weather that occurred during the previous 75 and 80 years reoccurred for the 12 locations studied. Soil quality, as measured by plant-available stored soil moisture at planting time (4, 7, and 10 inches), impacts corn yield much more for locations in this transect than it does for midwest Corn-Belt states (11). All locations, except Brookings, had many low and zero yields when plant-available stored soil moisture at planting was 4 inches. Low and zero yields increase in frequency for later tassel dates when plant available stored soil moisture at planting was 4 inches and even when it was 7 inches. Irrigation is necessary to produce acceptable yields at the Raymondville, TX, location (Fig. 2). High corn yields are more likely to occur for these locations for years when 10 inches of plant-available stored soil moisture at planting is present, particularly when early planting produces an early tasseling date.

• Highest yields occurred with the earliest tasseling date for all locations.

• In general, yields decrease more rapidly and year-to-year yield variation increases for the more southerly locations in the transect.

• Yields are more variable at all plant-available stored soil moisture levels at planting on this north to south transect than they are for Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin Corn-Belt locations (11).

• Irrigation was not examined for any impact it might have on corn yield for locations along the transect. The model does allow for determining how yields will respond under irrigation (11,12).

• Results for the Brookings location have the highest positive trend and least year-to-year corn yield variation for all tasseling dates and for all transect locations.

• Year-to-year yield variation is greatest for 4 inches, intermediate for 7 inches, and least for 10 inches of plant-available stored soil moisture at planting time for all locations.

• Year-to-year yield variation for the Brookings location decreases with later planting dates while it increases for all other transect locations.

Literature Cited

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10. Runge, E. C. A., and Benci, J. F. 2008. Forecasting corn yield for eleven states in the corn belt: Results for 2001-2005. Online. Crop Management doi:10.1094/CM-2008-0609-03-RS.

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