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Corn Production and Strip-Tillage in the Western Plains
An Emphasis on Irrigation Management, Fertilizer Placement, Soil
Health, and Drought Tolerance in a Challenging Environment
Corn, sorghum, soybeans, small grains, alfalfa, sunflowers, and
many other crops are grown in the semi-arid environment of the
central Great Plains and southern High Plains. Natural
precipitation is often deficient in the Great Plains. A harsh,
unpredictable, and diverse climate in these Plains areas makes
the production of corn and other crops challenging and risky.
Strip-tillage is a production option that can improve yield
potential due to realized benefits in irrigation use efficiency
and better soil and plant health.
Background
Annual rainfall from the Front Range of the Rocky Mountains in
Colorado to Eastern Kansas varies from 16 inches to approximately
32 inches, respectively [1,2]. These precipitation values are
less than one-half compared to annual precipitation in much of
the Corn Belt. During the summer months, it is common to
experience several continuous weeks of daytime temperatures in
the high 90s F and low relative humidity levels (< 20%) in
parts of the region. Combined with winds in excess of 15 mph, and
exposed soils, evaporative losses in the area can exceed 0.50
inch per day. Despite the challenges of limited natural
precipitation and compaction layers (soil health) also affect the
ability of the high evapotranspiration (ET), the area is
particularly well-suited for corn production. Long days that are
filled with sunshine and low humidity, and cool nights (50s F)
are ideal for sugar production. But the shortage and variation in
year-to-year precipitation and high ET rates requires many
producers to rely on irrigation to increase and stabilize crop
production.
One of the highest ET rates in North America was recorded near
Bushland, Texas, at 0.6 inch per day [3]. The Central High Plains
(Western Kansas, Eastern Colorado, and Southwestern Nebraska) can
experience 2.52 inches per week of ET for several weeks at a time
with little or no rain. Corn, grain sorghum, beans, and small
grains can all wilt and suffer yield loss, damage, and
occasionally premature death in such growing conditions.
Synergistic interactions between improved agronomic practices,
notably irrigation management, fertilizer placement, soil health,
and plant breeding efforts, such as drought tolerance, may help
to mitigate some of the environmental challenges and improve
yield potential in the area.
Water, Soil Health, and Plant Health
The relationship between corn plants and their soil environment
is critical to successful irrigation management and subsequent
yield potential. Total seasonal water use, daily crop water use,
the rate of plant development, and rooting depth (plant health)
all affect growth and development. In turn, a healthy plant is
able to extract more water from the soil and improve yield
potential. Soil water holding capacity, water intake rate, and
the presence of any compaction layers (soil health) all affect
the ability of the crop to utilize water and can affect yield
potential. Water quantity and quality are also important factors
in soil and plant health. Irrigation water quantity may affect
crop productivity more than any other factor, including choice of
hybrid, fertility, and weed management.
Irrigated Corn, Population Growth, and Limits on Water
The Ogallala Aquifer provides water for approximately 13 million
irrigated acres of farmland in the region [4]. The aquifer is the
world's largest underground water system providing drinking water
to parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma,
South Dakota, Texas, and Wyoming. Initially, water supplies
seemed limitless, but in the 1990s the wells began to lose
output. A severe drought period from 1998 through 2007 further
challenged traditional irrigation management practices, and the
Ogallala Unconsolidated Aquifer began to run low. Limitations in
the supply of precipitation and irrigation combined with other
harsh environmental parameters required attentive and adaptive
crop management practices.
Some of the key differences between corn production in central
Great Plains and southern High Plains compared to the central and
eastern Corn Belt include irrigation management, tillage, residue
management, fertility, soil health, and hybrid selection.
Conservation-tillage and strip-tillage have been gaining
popularity in the Plains region during the past decade (Table 1,
download the PDF to view illustrations) partly due to soil
improvements and corn production innovation.
Corn Production and a Strip-Tillage Approach
Strip-Tillage Defined
Strip-tillage, or strip-till, is a form of vertical zone tillage
that combines the benefits of zero-tillage and
conventional-tillage. Narrow row strips, usually 8 to 10 inches
wide and 8 to 12 inches deep, are tilled by way of a residue
cutting coulter and a soil displacing mole knife. The area
between the rows is undisturbed, while the tilled strips
correspond to planter rows. Fertilizer may be injected into the
tilled area during the strip-tilling process. Due to the demand
for grazing stalks in the fall, strip-tillage practices in the
Western Plains are commonly performed in the spring.
Benefits of Strip-Tillage
Some of the more immediate benefits of strip-tillage include the
field-wide preservation of soil colloids, soil pores, and root
channels from previous crops. Strip-tillage also helps to
preserve crop residue which aids in the buildup of soil organic
matter. Additionally, the presence of large pores in the
soil increases water percolation and improves crop rooting.
Long-term research studies conducted at the Irrigation Research
Foundation (IRF) in Yuma, CO, from 2003 to 2008 showed that
utilization of strip-tillage and strategic fertilizer placement
improves the three facets of yield potential: water, soil, and
plant health. Soils that were managed under strip-tillage
conditions had more beneficial worms per square foot, more
frequent and larger soil pores per square inch, greater percent
organic matter, faster water infiltration rates, and greater crop
yields compared to soils that were managed under
conventional-tillage. Strip-tillage acreage in the Great
Plains has greatly increased since the year 2000.
Improvements in Fertility
Growers manage the economics of fertilizer inputs. With
strip-tillage, the focus is to place it right within the
root-zone for immediate uptake.
In order to grow a larger and more effective root system and
healthier plant, nutrients should be readily available. Roots
placed in close proximity to nutrients allow plants to
thrive. Plants will expend more energy to grow and produce
grain when nutrients are not available close to the plant. With
the strip-tillage system, growers can place fertilizer within the
tillage band, at different depths to feed the plant. By
precisely placing fertilizer, the grower can take advantage of
more moist conditions in order for the nutrient to go into soil
solution to access it by the roots. With knowledge gained from
studies conducted at the IRF, researchers were able to use less
total nitrogen (N), phosphorus (P), and potassium (K) to obtain
equal or better corn yields in a strip-tillage system compared to
the common approach of broadcasting fertilizer. Results have been
expressed in deeper roots, more total root inches and consistent
higher yields. In addition to the IRF studies, research was
conducted at a private farm near Mingo, KS and at the Kansas
State University Northwest Research Extension Center near Colby,
KS.
Weather Patterns 2001-08.
A widespread drought affected crop production across western
Nebraska, Colorado, western Kansas and the Texas panhandle during
the first five years of the study period. Winter moisture was
generally limited and accompanied by above-normal temperatures
and wind. Spring and summer rainfall was generally deficient
compared to long-term averages for these periods. Summer
temperatures exceeded 100 F numerous times during several growing
seasons. In 2003, the daytime temperature exceeded 100 F for more
than sixty contiguous days. Irrigation well levels dropped and
some pivots were not able to supply adequate water for crop use.
In some cases, one-half of a pivot was abandoned to increase
water supply to the other half.
Study Guidelines
Large plot trials were conducted during 2001 through 2008 to
evaluate strip-tillage and conventional-tillage practices in the
context of soil and plant health. Studies were performed in full-
and limited-irrigation environments for six of the seven years.
Limited irrigation water studies were conducted with Dr. Freddie
Lamm of KSU Colby, KS at the Northwest Research and Extension
Center and with a grower Mark Myers near Mingo, KS. A
short- and long-season corn hybrid were included in some of the
test years. Standard agronomic practices were followed for
each tillage system. Standard corn hybrid products with a
relative maturity appropriate to the area were selected for use
in the studies. Conclusions should be drawn with the
qualification that results are from multiple-year, non-replicated
studies.
Results and Discussion
Soil Health
Soils that were managed under strip-tillage had reduced
compaction compared to soils that were managed under
conventional-tillage. Soil pores hold the air and water necessary
for plant growth. Compacted soils are dense and had smaller pores
compared to healthy soils. Compacted soils have reduced
infiltration rates, and resulted in ponding and crusting after
moderate to heavy rainfall (Figure 1, download the PDF for
illustrations). Plants were less able to extract nutrients from
compacted soils. Soil compaction was measured in units of
pressure (pounds per square inch (PSI). Root growth may become
restricted at 290 PSI, and corn roots can have difficulty
penetrating soils with a PSI rating greater than 400. Soil
compaction levels were measured five times at soil depths of
between one to six inches, seven, and eleven inches with a
penetrometer. Soils were 36%, 53%, and 73% less compacted at the
three sampling depths, respectively, under strip-tillage
management compared to conventional-tillage (Figures 2 and 3,
download the PDF to view illustrations).
Soils that were managed under strip-tillage had better water
percolation rates compared to soils that were managed under
conventional-tillage. Macropores are small, open channels in the
soil created by earthworm activity, soil cracking, and old root
growth. Tillage destroys macropores by mixing or disturbing the
upper soil profile. The preservation of root channels, soils
pores, and other holes in the soil profile leads to better water
infiltration (Table 2). As water percolation improves, surface
runoff decreases, leading to gains in irrigation and rainfall
water management and efficiency. Improvements in water management
can help to maintain the optimum soil moisture for growth,
reproductive development and yield potential.
The average time for one inch of water to infiltrate a dry soil
managed by strip-tillage was 1.1 minutes compared to 3.5 minutes
for a soil managed under conventional tillage (Figure 4). A
similar trend was observed for water infiltration into a soil at
field capacity (Figure 5).
Plant Health
Corn plants that were managed under strip-tillage had more roots
and rooted to greater depths compared to plants that were grown
in soils managed under conventional-tillage. Improved soil
quality allows for better root growth. A large root system
results in greater root-soil contact for improved water and
nutrient absorption. This is especially true for immobile
nutrients such as phosphorus and potassium. Furthermore, a large
and deep root system may be the mechanism by which corn plants
grown in strip-tillage environments have greater rooting depths
compared to plants grown under conventional tillage (Figure 6).
Large root systems are able to acquire nutrients and water while
supporting above-ground growth. The extended drought which
lasted from 1999 through 2006, had extremely limited moisture
during 2002 and 2003 growing seasons. Corn plants that were grown
in soils managed with strip-tillage practices produced between
10,000 and 28,000 total linear inches of roots per plant compared
to 3,200 and 10,000 total linear inches in conventional tillage,
in 2002 and 2003, respectively (Figure 7).
Corn plants that were managed under strip-tillage along with a
small amount of starter fertilizer and deep placement of
phosphorus (P) with a strip-tillage mole knife had greater yields
than corn plants that were grown under conventional-tillage with
broadcast fertilizer.
Starter fertilizers can help to mitigate the conditions of
reduced growth rates, lack of nutrient mobility, and decreased
nutrient mineralization that may occur in cool, wet soils.
Starter fertilizer, especially in cool soils, tends to support
early-season growth and vigor in corn. The fertilizer meets early
demands of the seedling until the root system develops, and its
placement is important to avoid injury to germinating
seedlings.
Application below the soil places P in the soil volume where it
can be easily accessed by corn roots (Figure 8). Furthermore,
concentrated zones of P can decrease P fixation, making it more
readily available for plant uptake. It is estimated that
approximately 50% of yield gains observed with the adoption of
strip-tillage can be attributed to the efficient banded placement
of fertilizer. The other 50% of yield gain can be
attributed to overall improved soil health and water holding
capacity.
Strip-tillage Yield Summary
FULL IRRIGATION STUDIES:
The objective of this study was to determine whether strip-
tillage could equal or improve upon conventional-tillage yields.
Dry land corn growers often employ a no-tillage system to
maximize soil moisture storage for corn growth and minimize
moisture loss as an effect of tillage. Corn under
irrigation is typically a good producer of grain yield and
residue. Strip-tillage practices are an option to take advantage
of minimum tillage practices while planting corn in heavy residue
conditions. Several advantages to strip-tillage compared with
conventional-tillage were observed including fewer tillage
passes, improved soil quality characteristics, and reduced
operator and equipment time. Yield increases were also
observed when fertilizer was applied below the plant and under
the planted row. Later measurements demonstrated that corn roots
under strip-tillage grow faster and deeper, compared to roots
searching for nutrients placed adjacent but not in the row.
Growing seasons varied from 2001 to 2006 with continued drought
and high summer temperatures. Hail damage prior to pollination in
2004 reduced leaf area and decreased yields. Lack of nitrogen and
Goss?s wilt disease pressure during 2006 and 2007, respectively,
and compromised data and results are not included for those
years.
Corn yields showed a positive response to strip-tillage and were
greater than conventional-tilled plots in all years except 2006
when nitrogen was limited to 0.50 lb/bushel of grain and less
available under strip-tillage due to organic matter
decomposition. Strip-tillage yields were measured and found
to often surpass conventional-tillage yields. Additional benefits
of strip-tillage systems included improved soil quality and plant
health, reduced soil erosion, and reduced operator and equipment
costs.
LIMITED IRRIGATION STUDIES:
These data are an average of limited water yields over locations
(IRF, KSU-Colby, KS and Mark Myers, Colby, KS). Data were
averaged across the short- and long-season hybrids when
available. Limited irrigation level was designed to supply
approximately 80 percent of the consumptive water need of a
full-watered corn crop, placing the corn under drought stress,
but allowed corn production even under drought and heat
environments. While yields varied across years and
locations, generally strip-tillage management had greater yields
compared with conventional-tillage management. The
increased yield under strip tillage was likely attributed to
improvements in soil quality, deeper rooting, improving plant
health and increasing water infiltration rates. Strip-tillage
management allowed more water storage for corn growth under arid
conditions.
Irrigation was reduced to 66% of consumptive use at the IRF
during test years 2003 through 2008. A portion of these trials
incorporated a short and long-season hybrid component, thus the
yield data was averaged across hybrids when available. Corn
yields were decreased when irrigation was limited to only 66%
compared to fully irrigated practices at the IRF. The soil
quality, plant health and soil water storage advantages of
strip-tillage were significant as heat and drought deteriorated
growing conditions compared to conventional-tillage plots.
Yields decreased as irrigation levels dropped, and strip-tillage
produced more bushels of corn per inch of water compared to
conventional-tillage management.
Sources
[1] Doesken, N.J. 2007. Colorado weather and climate
update. Colorado State University (presentation).
[2] U.S. Climate Data. 2011.
Climate-SalinaKansas.www.usclimatedata.com (verified
4/8/2011).
[3] Prasanna, H.G. et. al. 2008. Surface energy balance
based evapotranspiration mapping in the Texas High Plains.
Sensors, 8:5186-5201.
[4] Mcguire, V.L. 2007. Ground water depletion in the High
Plains Aquifer. USGS Fact Sheet 2007-3029.
Acknowledgements
We would like to thank all those whose contributions to this
research has made this research summary possible. Employees at
the IRF, Case New Holland, Orthman Manufacturing, Inc., and
Monsanto have been especially involved in this research and their
time and efforts are greatly appreciated.
Contacts:
Jeff Tichota Phone: 1-303-324-4941 Email:
jeffrey.m.tichota@monsanto.com
Mike Petersen Phone: 1-308-325-3474 Email:
mpetersen@orthman.com
Individual results may vary, and performance may vary from
location to location and from year to year. This result may not
be
an indicator of results you may obtain as local growing, soil and
weather conditions may vary. Growers should evaluate data
from
multiple locations and years whenever possible.
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2011 Monsanto Company. SEK4.8.2011.