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Use of Precision Irrigation to Maximize
Grower Profits and Manage Disease in
Pathogen Infested Soils
Yields
in irrigated crops typically exceed non-irrigated acres
by more than 50%.
In Texas, the average yield increase of irrigated verses
non-irrigated production is 61% for peanuts, 79% for wheat,
81% for corn, and 122% for cotton. Because of the importance
of irrigation to high production agriculture in the Texas
Panhandle and much of the Western United States -- highly
efficient irrigation systems, sensitive instrumentation
for quantifying plant stress, and irrigation equipment capable
of variable rate applications have been developed to maximize
water use efficiency.
However, when crops are grown
in pathogen- infested soils -- root disease can totally
disrupt a plant's ability to efficiently use available
soil water.
The
Primary Focus
of
the plant pathology precision agriculture project at Bushland
has been to investigate the relationships between irrigation,
disease incidence, and crop yield.
In the last three years,
we have evaluated the effect of various PET-based irrigation
levels on crop yields, water use efficiency and disease
development in corn, sorghum, sugar beets, and wheat.
With
all grain crops, we found yields from plots irrigated
at 75% PET often equal or exceed those irrigated at 100%
PET. Even when grain yields are lower at 75% PET, final
profit for growers can be higher because of reduced pumping
costs. During the 2000 growing season, 24.2 inches of
water were applied to sorghum irrigated at 100% PET while
only 19.4 inches were applied at 75% PET. Currently, it
costs approximately $7.50 to pump an acre-inch of irrigation
water, and at this cost, sorghum growers in 2000 applying
75% PET saved approximately five inches of water and $37.00
per acre in reduced irrigation costs. For corn, savings
at 75% PET were seven inches of water and $52.00 per acre
in pumping costs.
And the farmers bottom
line?
If
these savings were applied to all irrigated corn and sorghum
produced in the northern 21 counties of the Texas Panhandle
-- the 5 acre-inches saved over 250,000 acres of irrigated
sorghum and 7 acre-inches saved over the 900,000 acres
of irrigated corn would equal approximately 200 billion
gallons of water conserved and 56 million dollars.
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Principal Investigator:
Charles M. Rush Plant Pathologist
Texas Agricultural Experiment Station
Amarillo (Bushland)
Other savings ...
In addition to direct savings achieved
by reducing pumping costs, we
have found that less irrigation reduces the incidence
and severity of several plant diseases and also insect populations.
Reduced irrigation frequency limits many soilborne plant pathogens
because the soil has a chance to dry to a point where the
pathogen's ability to move through the soil to new infection
sites on the host plant is significantly reduced. Conversely,
at 100% PET, soil conditions favor pathogen movement and increased
disease incidence and severity results.
Research impact ... We
have demonstrated successfully that producers cannot irrigate
crops growing in pathogen-infested soils in the same manner
they irrigate crops growing in pathogen-free soils.
At Bushland in 2000, our study showed that irrigation rates
can also impact aphid-vectored virus diseases. At 100% PET
and low plant populations, greenbugs were significantly more
abundant than in sorghum plots with higher plant populations
and 50% PET. Regardless of plant population, greenbug abundance
always was less at 50% PET than at 75% or 100% PET. Furthermore,
we observed that plants irrigated at 100% PET had a significantly
higher incidence of maize dwarf mosaic virus (MDMV) than those
irrigated at 50% PET.
Future
research focus ... will
include the relationship between plant population and irrigation
rate with aphid populations and virus diseases, not studied
previously.
For
more information about this project, contact:
Charles
M. Rush, PhD Plant Pathologist
Texas Agricultural Experiment Station
2301 Experiment Station Road Bushland, TX 79012
PHONE: (806) 354-5804
FAX: (806) 354-5829
EMAIL: cm-rush@tamu.edu
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