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DIVISION
rekE P 0 P T
Evaluation of Dryland Corn and Grain Sorghum Production
In the Southern Plains Using Computer Simulation
This Research Report, RMN SORGHUM IS THE TRADITIONAL SUMMER GRAIN
crop under dryland conditions in the Southern High Plains. However,
97-4, is contributed by the there has been a growing interest in recent years in dryland corn.
D 1 2There has been very limited research in recent years in the Texas
High Plains with dryland corn, so there is a lack of current
Auriculture experimental data to share with producers. Jones and Thaxton 1950 conducted
dryland vanetal tests for corn and grain sorghum at Lubbock, Texas, from 1942-48.
Institute The years of 1945, 1946 and 1948 were extremely dry. Therefore, very little yield
data were recorded for all varieties of diyland corn and grain sorghum. For one corn
>1 West Texas A&l University, hybrid, the average yield over eight years was 1,040 pounds per acre with the highest
yield 2,300 pounds per acre in 1942. For grain sorghum, the average yield was 1,450
Canyon, Texas, and the pounds per acre with the highest yield 2,450 pounds per acre in 1942. Annual
precipitation totaled 27.3 inches in 1942 compared to the avearge of 18.8 inches. A
Texas Agricultural Experiment Station, long-term dryland crop rotation study was conducted in Dalhart, Texas, from
1908-38. Mathews and Barnes 1940 reported 30-year average yields of 1,070
The Texas A&M University System pounds per acre for dryland corn and 2,100 pounds per aae for grain sorghum
grown under a fallow system. In the same study, the average corn and grain sorghum
Agricultural Research and Extension yields for three different methods of cultivation on continuously cropped land were
800 and 1,230 pounds per acre, respectively. Average annual precipitation for the
Center. Anarillo, Texas. 31-year study was 17.5 inches; it is worthy to recall that this period included the
severe drought period of the 1930s. Dryland corn yields ranged Irom 0 in 1933 and
Financial support for the study 1934 when the annual precipitation was only about 10 inches to 3,650 pounds per
acre in 1915 when the annual precipitation was 21 inches. Mathews and Barnes
was provided by the 1940 further reported that corn was more productive at Daihart, Texas, than at most
of the other southern dryland field stations. They concluded that corn was an
Texas Grain Sorghum Board and important dryland crop at higher elevations where summers were cooler, and the
date of the first killing frost was earlier than in Dalhart.
the Texas Corn Producers Board.
Computer Simulation StudyBecause weather is extremely variable, it will require several years of field data
before sound recommendations can be made based on studies using new varieties of
corn and grain sorghum. Modern hybrids and improved cultural practices have
greatly improved the yield potential of both crops, even under dzland conditions.
Computer simulation crop models are available that can analyze soil-crop-climate
interactions. This study used the Erosion Productivity Impact Calculator l-l'IC to
simulate corn and grain sorghum production for 50 years so that the two crops could
be compared for years of widely varying climatic conditions. The results will provide
A klest Texas A&IVI growers information that may be useful during the period that additional field studies
Ware being conducted. Field results for grain sorghum from Bushland, Texas, Stewart
U N 1 V E R S I T `` and Steiner, 1990 and for corn from Akron, Cob., Nielsen, 1995 were used to
validate that the model simulated yields were realistic.
AGRICULTURE
A Memb of The Texas MM Uriwersity System
Simulations were made for five Iocations-Dimmitt, Texas; Bushland, Texas;
Boise City, Okia.; Tribune, Kan.; and Akron, Colo.-ranging from south to north in
the Southern High Plains. Climatic characteristics for the different locations are
presented in Table I. Although all five locations are predominantly summer rainfall
areas, there are some distinct differences in the distribution patterns.
Table 1. Average elevation E, monthly and annual precipitation, and growing
season days GSD for study locations
E Precipitation GSD
Location Feet J F M A M J J A S 0 N I T Days
Inches
Dimmitt, Texas 3,850 0.27 0.37 0.80 1.04 3.13 2.45 1.94 2.67 2.78 2.08 0.73 0.42 18.68 201
Bushland, Texas 4,000 0.51 0.51 0.78 1.01 2.67 3.00 2.69 2.81 1.93 1.53 0.73 0.58 18.74 205
Boise City, OkIa. 4,170 0.44 0.66 0.95 1.55 2.73 2.90 2.82 2.57 1.92 1.81 0.86 0.58 19.79 184
Tribune, Kan. 3,600 0.21 0.42 0.84 1.56 2.54 2.65 2.43 2.02 1.43 0.92 0.48 045 15.96 164
Akron, Cob. 4,580 0.30 0.35 0.83 1.69 3.00 2.48 2.72 1.97 1.22 0.91 0.55 0.43 16.50 143
Moving from south to north, less precipitaion occurs in late summer and early
fall. This can be clearly seen in Figure I J.T. Musick, USLA-ARS, Bushland, Texas,
personal communication that shows 15-day precipitation totals by three-day periods
for selected locations in the southern and central Great Plains. The southern-most
locations have a definite two-peak precipitation pattern, but the second peak becomes
clearly less pronounced for locations further north.
Planting dates used in the model for corn ranged from April 10 in the south to
May 10 in the north compared to grain sorghum planting dates ofJune I in the south
toJune 10 in the north. The dominant soil type for each area was used in the model,
and it was assumed for each year that the plant available soil water storage onjan. I
was 50 percent of maximum. This assumption was made because it is generally
accepted that dryland corn should not even be considered unless there is substantial
stored soil water at the time of planting.
ResultsAverage yields and range of yields for the 50 simulated years are presented in
Table 2. Average grain sorghum yields were higher for the southern locations while
average corn yields were higher for the northern locations. As discussed earlier,
rainfall distribution varies from south to north, and this is believed to be a major
reason for sorghum doing better in the south and corn better in the north.
Distribution of rainfall for various locations shown in Figure 1 illustrates that the
southern locations have a bi-modal distribution of precipitation while the northern
locations have a single-modal distribution. Since grain sorghum is seeded later, it
benefits from increased soil water storage from early rainfall, and late rainfall often
occurs during the heading and grain filling periods. In the northern locations, early
seeded corn receives most of the rainfall prior to maturing while early seeded corn in
the south does not benefit from late precipitation events. Also, temperatures are
cooler in the northern locations. Cooler temperatures are favorable for corn while
unfavorable for grain sorghum.
The 50 years of simulated yields represented a wide range of precipitation
amounts during the growing season. There is a direct relationship between seasonal
water use precipitation during the growing season plus stored soil water minus runoff
and drainage and grain yields. Although yields for any one year can fall above or
Figure 1. Average 15-day Precipitation Moving Totalsby Three-day Periods, January Through December, byMusick of the USDA Conservation and ProductionLaboratory, Bushland, Texas personal communication,1996
J F M A M J.J A $
08
3.4
01100
below the lines shown in Figure 2
because of the tunelineness of a
particular rainfall event, overall
relationships are represented by the
lines. These relationships indicate that
for grain sorghum, about six inches of
seasonal evapotranspiration are required
before any grain is produced, and for
each inch of additional water used,
about 350 pounds of grain are produced.
For corn, the relationship illustrated in
Figure 2 suggests that no corn grain is
produced unless at least eight inches of
evapotranspiration occurs, but for every
inch of additional evapotranspiration,
there are about 450 pounds of corn
grain produced. The point that the two
lines cross is about 17 inches with a
yield of approximately 4,000 pounds per
acre. This suggests that grain sorghum
would generally yield more than corn
when seasonal evapotranspiration is less
than 17 inches, and corn would yield
more when seasonal evapotranspiration
is more than 17 inches. Average
growing season rainfall for the locations
used in the study is about 10 to Ii
inches. This means that for years of
avenge precipitation, about six to seven
inches of soil water must be available to
meet the 17 inches needed for corn to
yield as much as grain sorghum. This
supports the recommendation that
dryland corn should generally not be
considered unless there is substantial soil
water stored at time of seeding. Even
then, corn yields are not likely to exceed
grain sorghum yields unless growing season precipitation is above avenge.
The findings of this study clearly suggest that there is more risk, particularly in
dry years, associated with corn at all locations studied. In general, grain sorghum
yields were less than 2,000 pounds per acre only about one year out of nine while
corn yields were less than 2,000 pounds per acre about one year out of three except
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Table 2. Average Yields of Corn and Grain Sorghum for Five Locations in theSouthern High Plains for 50 Years of Varying Climatic Conditions
Location Corn Range Sorghum Range Corn/Sorghum
Pounds Per Acre Pounds Per Acre Ratio
Dimmitt, Texas 3,150 630-7,020 3,780 1,620-6,390 0.88
Bushland, Texas 2,340 450-4,860 2,610 990-4,860 0.89
Boise City. OkIa. 2,610 540-5,940 3,060 1,170-5,400 0.85
Tribune. Kan. 3,690 1,080-6,210 3,420 1.710-5,130 1.07
Akron, Cob. 3,060 810-5,400 2,610 1,260-3,870 1.17
Figure 2. Generalized RelationshipBetween Corn and Grain Sorghum Yieldsas a Function of Seasonal Water Use inthe Texas High Plains
10000
8000
6000
4000
2000
0
for Tribune, Kan., where yields nearly always exceeded 2,000 pounds per acre for
both crops. Even at Tribune, however, grain sorghum yielded more than corn in the
driest years. For all locations, corn produced more grain than grain sorghum for the
years when growing season precipitation was very high.
The study suggests that long-term average grain yields
of corn will be about 87 percent of those of grain sorghum in
the south portions of the Southern High Plains but will be
about 112 percent of those of grain sorghum in the northern
locations. However, there is clearly more risk with corn
during dry years. On the basis of yield alone, grain sorghum
would be the logical crop of choice for producers in the
south, and corn would be the preferred crop in the north.
However, profit is the goal of the producer, and profit is a
function of yield, production costs and price of the product
Corn prices are often significandy higher than grain
sorghum, particularly for early produced corn. This study
considered only yield; economics will require additional
analysis. We conclude that dryland corn should not be
considered unless there is substantial stored soil water at
time of seeding, and even then, corn yields will likely not be
significantly higher than grain sorghum unless growing
season precipitation is above average. However, corn yields
can be signigicantly higher than grain sorghum in years of
high precipitation. Growers that have high amounts of soil
water stored at seeding time may very well want to plant some dryland corn, but it
may be prudent to plant at least part of their land to grain sorghum in the event that
growing season rainfall is below average.
-Mvsammad Add Ak.bar, WTAMU
-BA. Stewart, WTAMU
-CD. Salisbuiy, TAES
.2
0 4 8 12 16 20 24 28
Seasonal Evapotransplratlon inches
ReferencesJones, D.L and E.L. ThaxtonJr.
1950. Dry-land yields of grain sorghum
and corn at lubbOCk, 1941-48. Progress
Report 1229. Texas Agricultural
Experiment Station, College Station,
Texas.
Mathews, O,lt and B.F. Barnes.
1940. Dryland crops at Dalhart, Texas,
Field Station. USDA Circular No. 564,
Washington, DC.
Nielsen, D.C. 1995. Water
use/yield relationships for Central Great
Plains Crops. Conservation Tillage Fact
Sheet 2-95. USDA ARS, Akron, Cob.
Stewart, BA. andJ.L Steiner.
1990. Water use efficiency. P. 151-173.
In: Dryland Agriculture: Strategies for
Sustainability. Advances Soil Science,
Volume 13, Springer-Verlag, New
York.
Detath ofthe stady are reported in a
thesis submitted in partialfi4iJinent of
requ zrnrtentsfor a Master ofScience is
Agricatare degree, West Texas A&M
Uniuersity, 1996.