|
Using Limited Irrigation for Crop Production
in the Central Great Plains
J.G. Benjamin, D. C. Nielsen, M. F. Vigil
PROBLEM: Irrigation water supplies in the central Great
Plains of the United States continue to diminish due to use by farmers and
additional demands for these water resources by urban areas. We envision that
farmers will have less water available for irrigation in the future. Water
resources need to be managed such that we maximize production for each unit of
irrigation water. It is well recognized the there are critical periods during a
crop’s life cycle were minimizing water stress results in maximum yield. Several
researchers have proposed limiting the application of irrigation water to these
periods. Less in known about the long-term effects of limited irrigation on soil
productivity and the sustainability of limited irrigation systems.
APPROACH: We continued an irrigation - tillage experiment
that was started in 2000. An early snow and freeze in the fall of 2001 prevented
the tillage treatments from being applied. The rotation plots in the experiment
were planted to spring barley in 2002. The remaining plots were planted to corn.
Half the field received full irrigation as determined from ET estimates and the
other half of the field receiving no irrigation until the crop started to
flower. After flowering the entire field received full irrigation based on
estimated ET. Soil moisture content measurements using the neutron scatter
technique were taken twice per week, immediately before irrigation and shortly
after irrigation. The plant growth characteristics for corn and barley that were
measured during the growing season included weekly leaf area index (LAI)
measurements and biomass measurements at flowering and at maturity. All plots
were harvested at maturity for grain yield. The tillage treatments were applied
in the fall of 2002 by deep chiseling the tilled plots 14" deep.
RESULTS: The year 2002 was a very difficult year for this
experiment. An extended drought occurred that subjected the crops to unusual
water stress. Also, by being a relatively green area in a large region of brown,
drought-stressed crops, we had much more wildlife damage than normal. In some
plots deer and 13-striped ground squirrel activity reduced plant stands to less
than 14,000 plants per acre from the 32,000 plant per acre usually planted. A
hail storm occurred on August 24 which was at the R2 growth stage of corn. The
LAI in the fully-irrigated corn plots was reduced from about 4 to about 2. The
LAI in the partially-irrigated corn plots was reduced from about 2.5 to about 1.
Crop yield were reduced accordingly. The mean corn yield for the fully-irrigated
plots and the partially-irrigated, no-till plots were the same at about 80 bu/ac.
The partially-irrigated, chisel plow plots has a grain yield of about 55 bu/ac.
The fully-irrigated barley plots yielded about 55 bu/ac and the
partially-irrigated barley plots yielded about 45 bu/ac.
FUTURE PLANS: We will continue the experiment in 2003. The crops will be
corn in the continuous corn plots and sunflower in the crop rotation plots. We
will install neutron access tubes in each plot to better evaluate water stress
and irrigation efficiency. Other measurements of crop emergence, LAI, biomass,
yield, and soil properties will remain the same. We are particularly interested
in the cumulative effects of partial irrigation on the early plant growth when
the current crop is planted on a soil depleted of water by the previous crop.
The authors may be reached via e-mail:
J.G. Benjamin,
D. C. Nielsen,
M. F. Vigil
or phone: 970-345-2259. |